摘要:

Journal of Materials Chemistry Scientific Advisory Editor Professor Martin R. Bryce Department of Chemistry University of Durham South Road Durham DH1 3LE, UK Associate Editor Professor Jean Etourneau lCMCB Avenue du Docteur Schweitzer 33600 Pessac France Editorial board Allan E. Underhill (Chairman) Bungor Neil L. Allan Bristol Peter G. Bruce St. Andrews Martin R. Bryce Durham Michael J. Cook Norwich Managing Editor Janet L. Dean Deputy Editor Zoe G. Lewin Assistant Editor Graham F. McCann Editorial Secretary Miss D. J. Halls Jean Etourneau Bordeaux Wendy R. Flavell UMIST Colin Greaves Birmingham Philip Hodge Manchester Stephen M. Kelly Hull International advisory editorial board K. Bechgaard Rise, Denmark J.Y. Becker Beer-Sheva, Israel A. J. Bruce Murray Hill, USA E. Chiellini Pisa, Italy D. Coates Poole, UK P. Day London, UK D. A. Dunmur Shefield, UK B. Dunn Los Angeles, USA W. J. Feast Durham, UK R. H. Friend Cambridge, UK A. Fukuda Tokyo, Japan D. Gatteschi Florence, Italy J. W. Goodby Hull, UK Information for authors The Royal Society of Chemistry welcomes submission of manuscripts intended for publication in two forms, Articles and Materials Chemistry Communications. These should describe original work of high quality dealing with the synthesis, structures, properties and applications of materials, particularly those associated with advanced technology. Full papers contain original scientific work that has not been published previously.However, work that has appeared in print in a short form such as a Materials Chemistry Communication is normally acceptable. Four copies of Articles including a top copy with figures etc. should be sent to the Managing Editor at the Cambridge address. Journal of’ Materials Chemistry (ISSN 0959-9428) is published monthly by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK. All orders accompanied with payment should be sent directly to The Royal Society of Chemistry, Turpin Distribution Services Ltd., Blackhorse Road, Letchworth, Herts SG6 lHN, UK. NB Turpin Distribution Services Ltd., distributors, is wholly owned by The Royal Society of Chemistry. 1996 Annual subscription rate EEA (incl.UK) E519.00, USA $934.00, Rest of World E532.00. Customers A. B. Holmes Cambridge, UK H. Inokuchi Okazaki, Japan W. Jeitschko Munster, Germany 0.Kahn Bordeaux, France J. Livage Paris, France R. McCullough Pittsburgh, USA J. S. Miller Salt Lake City, USA K. Mtillen Mainz, Germany L. Niinisto Espoo, Finland M. Nygren Stockholm, Sweden Y. W. Park Seoul, Korea N. Plat6 Moscow, Russia M. Prato Trieste, Italy Materials Chemistry Communications contain novel scientific work in short form and of such importance that rapid publication is warranted. The total length is normally restricted to two printed A4 pages. However, special consideration will be given to communications with a large amount of essential diagrammatic information.Submission of a Materials Chemistry Communication can be made either to the Managing Editor at the Cambridge address, or oia a member of the International Advisory Editorial Board. In the latter case, the top copy of the manuscript including any figures etc., together with the name of the person to whom the Communication is being submitted, should be sent simultaneously to the Managing Editor at the Cambridge address. All authors submitting work for publication are should make payments by cheque in sterling payable on a UK clearing bank or in US dollars payable on a US clearing bank. Air freight and mailing in the USA by Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003.USA POSTMASTER: send address changes to Journal of Materials Chemistry, Publications Expediting Inc., 200 Meacham Avenue, Elmont, NY 11003. Periodicals postage paid at Jamaica, NY 11431. All other dispatches outside the UK by Bulk Airmail within Europe, Accelerated Surface Post outside Europe. PRINTED IN THE UK. Editorial Production Coordinator Stephanie Shah Technical Editors Carole J. Nerney Alan J. Holder Jeff R. White Graphics Designer Ms C. Taylor-Reid Klaus Praefcke Berlin Anthony R. West Aberdeen Janet L. Dean (Secretary) C. N. R. Rao Bangalore, India B. Raveau Caen, France T. Rojo Bilbao, Spain J. Rouxel Nantes, France A. Simon Stuttgart, Germany M. A. Subramanian Wilmington, USA S. Takahashi Osaka, Japan J.0.Thomas Uppsala, Sweden M. Vallet-Regi Madrid, Spain D. E. W. Vaughan Annandale, USA J. D. Wright Canterbury, UK Y. Yamashita Okazaki, Japan required to sign an exclusive copyright licence. All submissions should be accompanied by a completed form (a blank for photocopying is reproduced at the end of the Information for Authors in Issue l), without which publication cannot proceed. A completed graphical abstract template should also accompany each submission. Full details of the form of manuscripts for Articles and Materials Chemistry Communications, conditions for acceptance etc. are given in Issue 1 of Journal of Materials Chemistry published in January of each year, on the world wide web (htpp://chemistry.rsc.org/rscj) or may be obtained from the Managing Editor. There is no page charge for papers published in Journal of Materials Chemistry. Fifty reprints are supplied free of charge. Janet L. Dean, Managing Editor Tel.: Cambridge (01223) 420066 E-Mail (INTERNET): DEANJ@RSC.ORG Fax: (01223) 420247 Advertisement sales: Tel. $44 (0)171-287 3091; Fax +44 (0)171-494 1134 0The Royal Society of Chemistry, 1996. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photographic, recording, or otherwise, without the prior permission of the publishers.

ISSN:0959-9428    

DOI:10.1039/JM99606FX045

出版商:RSC    

年代:1996

数据来源: RSC

ISSN:0959-9428    

DOI:10.1039/JM99606BX047

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

ISSN09 59-9428 Synthesis, structures, properties and applications of materials, particularly those associated with advanced technology CONTENTS Articles a-conjugating spacers in linearly extended hybrid tetrathiafulvalene analogues El Hadj Elandaloussi, Pierre Frltre, Amina Benahmed-Gasmi, Amedee Riou, Alain Gorgues and Jean Roncali 1865 Preparation and properties of epoxidized natural rubber/poly (c-caprolactone) self- vulcanizable blends Yasuhisa Tsukahara, Tomio Yonemura, Azanam Shah Hashim, Shinzo Kohjiya and Kyoji Kaeriyama 187 1 The synthesis and characterisation of a novel thiophene-based liquid crystal exhibiting ferro-, ferri- and antiferro-electric phase types David J. Byron, Lachezar Komitov, Avtar S. Matharu, Ian McSherry and Robert C.Wilson 1879 Preparation and characterization of Au-dispersed TiO, thin filmsby a liquid-phase deposition method Shigehito Deki, Yoshifumi Aoi, Hirashi Yanagimoto, Katsuyuki Ishii, Kensuke Akamatsu, Minoru Mizuhata and Akihiko Kajinami 1 JMACEP( 12) 1859-1969 (1996) c/) Qfis R WR R R + -cure ,elastometic materials Me t iiiiiiv

ISSN:0959-9428    

DOI:10.1039/JM99606FP126

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Cumulative Author Index Abe J Adamczyk B Agranat I Ahamdane H Airoldi C Akamatsu K Alano-Franco M A Albiston L Alcantara-Rodriguez M Ali F All-Adib Z Allen J L Allen K M Almond G G Almond M J Alonso P J Al-Raihani H Alves L Amari C Amarilla M J Andersch J Ando I Andreozzi G B Andrews S R Andrianainanvelo M.1665 Antonietta Massucci Beteille F Bianchi V Bickmore C R Bieniok A Bikchantaev I Blin J L Boggavarapu S Boiteux G Bomben A Bonnefond P Booth C Booth C J Borau V Bornholdt K Bosch P Boschi T Boulanger C Boutinaud P Bouwmeester H J MI Boyle D S Bradley D D C Branger C Bravic G Breen C Brendel U Brettle R Bntton D Chavez J A Chen C Chen F Chen J. 465. Chen K ChenL Chen X Cheng T R Chevieau A Chiba K Chippindale A M Chisholm M S Choi J U Choukroun R Chung D D L Chung H Clarkson G J Clearfield A Clemente D A Cockayne B Cohen S Cole-Hamilton D J Cole M Colgan D C Colley R A Collins D R.Du Y Dubois J Dumont B Dunmur D A Durand B Dusastre V Dussack L L Duvauchelle N Eadon D Eastmond G C Eckert H Egdell R G Eguchi K Einsiedel H Ekstrom T C Elandaloussi E H Elhsissen K T Ellert G Elsner J Enoki T Enomoto M Esmans E Espinet P Etter the late M C Eustace P Evans P Ewen R J Gerdanian P Gharbi N Gibb T C Gibson R Gilbart E Glenis S Glidle A Gogotsi Y G Goldenberg L M Gomi Y Gofii A Gonnet J P Gonsalves K E Goodby J W Gorbenko Y Gordon J Gore J G Gorgues A Goyal R Goui D Graboy I E Graham P Greaves C Green D A Green M A Green M L H Gregoire G M Brooks J S Condorelli G’ G Ezekwenna P Grenier J-C Aoi Y Aomine T Apperley D C Arai H Arai K Aramendia M A Aranda M A G Brouca-Cabarrecq C Brown C R Brown I W M Bruque S Brustolon M Bryce M R Budd P M Cook M J Cooke S Cooke S A Corbel S Cornu R Corm R J P Fache F Fahy M R FanY Fang M Fantoui G Farcy J Farr I V Gnjalva H Grobelna B Grobet P Grozdanov I S Guarrera D Guizard C Gulino A Aranha N Arc0 M d Ariza E Arnal P Arriortua M I Ashwell G J Attfield J P Budig H BuistG J Bujoli B Bujoh-Doeuff M Bukhtenko V Burggraaf A J Burn P L Busca G.Cot L Cowley A R Crayston J A Crespo I Crespo R Cuevas R F Dabadie T Dafadar M H Farrand L D Fawcett I D Febri M Ferey G Ferragma C Fetter G Feurer R Fievet F. GunDer W Guo L-H Gutierrez R Guzman G Haase W Haberle N Haggata S W Hahn J H Aymard L Ayral A Ayyappan S Babonneau F Bach S Bush T-S Bushnell-Wye G Byrn S R Byron D J Cabeza A Damiani D E DAndrea G Dann A J Dann S E Daolio S Fievet-Vincent F Fitch A N Flint S D Fompeyrine J Foran G J Hall S B Hamada D Hamer J C E Hamerton I Hamet J-F Baena M J Baert F Bafier N Cabrera S Cai S X Calabrese J C Darnet J Datun M Davies A Forder S Forester T R Fort A Hamilton D G Hamzaoui F Hanack M Bahloul-Hourlier D Bahra G S 23,969 Banister A J Baraton M-I Caldes M T Calestani G Calleja R D Calvert P Davies T W Davis F Davis F J Davis S J Foster D F Fournes L Fox J R Foxman B M Hara H Harding J H Hanno K Harkema S Barberis G E Barbosa L C Barcina J Barclay G G Bardosova M Barrans Y Barrel1 K J Barriga C Barris G C Barton J M Barzoukas M Bassoul P Bast1 Z Cameron N R Caminiti R Campbell S A Campillos E Campostnni R Carbone M Carfagna C Carleer R Carr S W Carroll S Carturan G Casal B Cassoux P Davison C M Dawson D H Deki S de Lacy Costello B P J Delahaye-Vidal A Delmas C de Paula A M de Souza D P F de Souza M F Destri S Detellier C Diaz L Fragala I Fragala I L Franke U Franklin K R Frauenheim T Fray S M Frere P Fryer J R Fujimoto H Fujiwara S Fukuda A Harris K D M Harris R K Harrison N M Harrison W T A.Hasegawa M Hasegawa N Hashim A S Hashimoto S Haugk M Hauptman Z V Hayashi H He H Bastow T J Castellanos M A Dickens P G Fun H-K Heald R C Battisti A De Battle P D Castiglioni M Catlow C R A Caurant D Diele S Dirken P J 1297. Furukawa T Gachard E Gallardo Amores J M Heatley F Henshaw G S Hepel M Baules P Baur W H Bay B H Bearchell C A Ceccato R Cellucci F Cerrini R Cesar C L Dixit M Domingues-Rodrigues Dommisse R A Gan L B Ganguli M Gao Q Gao Y Heppke G Heredia G Hernan L Hernandez V S Beaudoin B Chakrabarti N Dotze M Garcia J R Herrera-Urbina.R Behrens U Belloni J Benahmed-Gasmi A Bensamka F Chakravorty A K Chaneac C Chane-Ching K Chansou B Dou Y Dougherty J Doumerc J-P Douthwaite R E Garcia-Granda S GayD H Gazzoli D Geise H J Hersans R Hervieu M Hess A Benzi P Berry F J Bertoti Charters R B Chassagneux F Chasseau D Dragone R Drumel S Du H Gellman L J Gentle I R George C D Heyes S J Higgins B G Hillman A R Hinklin T R Hiraoki T Hirn B Hitch T J A R Hiyama T Hobson R J Hodge P Hoffmann R-D Ho-Hoang A Holloway A Holloway J Holmberg S Holmes P A Honeybourne C L Honta K Howie R A Howlin B J Hu Z Huang C H Huang J L Huang K-S Hubert Mutin P Hudson M J Hulinsky V Humberstone P Hunsinger J J Huve M Hyde T Ichikawa F Igarashi C Iglesias R Ihanus J 161,983 Iimura N Ikemoto I Imae I Kandori K Kannan T S Kanniainen T Kano S Karasu M Kanuki B M Kasthuraiah N Katerski A Kaul A R Kawaguchi K Keana J F W Keene M T J Kelder E M Kemnitz E Kennard C H L Khomenko G E Kikuchi K Kilian D Kim J H Kim S B Kitazawa T Klar G Klar P J Klinowski J Klissurski D G Knowles J Knowles J A Kochubey D I Kodenkandath T Koehler K Kohjiya S Kohler T Kohno M Komarneni S KlnJO N Li S Li X Lin C L Lin J Linda11 C M Lindroos S LiuC S Liu S Livage J Llavona R Lob0 C Loiseau T Lorriaux-Rubbens A Lose D Lougnot D J Loukatzikou L A Loveday D C Lowendahl L Lunkwitz R Lynch D E Machida M 69,455 MacKenzie K J D Macklin W J Madarasz J Madroiiero A Maeda Y Magri P Ma1 S-M Maignan A Mairesse G Maiti H S Maksimov Y V Malandnno G Li Y-J Miyazaki A Miyazaki K Mizuhata MI Moffat J B Mohai I Moine B Monk P M S Moon J H Mora A J Morales J Moran E Mon T Moriga T Morineau R Monoka H Morris L Mosel B D Mosset A Mueller B L Mulley S Mullmann R Muramatsu H Mutin P H Muto A NagaseY Nair G G Naito H Najdoski M Z Nakajima K Nakano H Nakaya T Nakazumi H Narayana Rao D Nasman J Nazabal V Pearson C Pedrini C Peeters K Pei Y Pelizzi C Pelloquin D Pelzl G Peng B-X Peng Z-H Pereira-Ramos J-P Perez-Rodnguez J L Perrin M-A Pertierra P Peters D Petric A Petrunenko I A Petty M C Phillips B Picard C Piccinllo C Pickett N L Piqueras M C Piszora P Pizarro J L Pohmer J Pola J Pomonis P J Poojary D M Porras A Portemer F Porzio W Pottgen R Powell A V Predieri G Prellier W Inagaki M Ingram-Jones V J Inman D Inoue H Inoue M Inoue Y Inui S Irvine J T S Komatsu T Komitov L Kooli F Koroglu A Koto K Koudijs A Koyama S Kremer R K Malet P Mancini N A Maniero A L Mann B E Manthiram A Marcelis A T M Marcomini A Marcos M Neat R J Needs R L Nemoto N Neumann B Newport R J 337,449 Nickel K G Nieminen M Nii H Pringle P G Pyzuk W Qian M Qun L R M A C Radaev S F Radhakrishnan T P Ishii K Ishikawa T Isozaki T Issiki TI Itaya A Itoh K Kreuzer F-H Krishnaprasad S Knstof J Krowczynski A Kruerke D Kruidhof H Mariappan L Marinas J M Marrot B Marson C M Martin C Martinez E S Niinisto L Niori T Nishida T Nishide T NomaN Nomura M Ramachandra Rao C N Ranjan R Rao C N R Rao K J Rasheed R K Iwane H Iyoda M Jackson P D Jacobson A J Jakob E Kubota J Kudnig J Kuroda K Kurosu H Kusumoto T Martinez J I Marucci A Marugan M M Marzotto A Matacotta F C Nortier P Nowogrocki G Nutz U Nygren M O’Bnen P Rasika Abeysinghe J Ratcliffe N M Rauhala E Rautanen J Jaleel V A Klonkowski A M Matar S F Oestreich S Raveau B James.M Janes R Jansson K Janvier P Jarmo Koivusaari K Labes M M Lacan P Lachowski E E Lagow R J Lai S-W Matharu A S Mather G C Matijevic E Matsubayashi G-e Matsui M Ogata H T S Ogawa K Ogura S Ohashi M OhN-K Ravi M Rawson J M Rawson J Razafitnmo H Jefferies G Jeitschko W Jiang H Jimenez C Jimenez- Lopez JobicH E R-C A Laine R M Lambrecht W R L Lang A Lanzetta R Laureiro Y Lavela P Lebuis A-M Matsuyama H Mattei G Maubert A M Maury F McCullough R D McKeown N B McLendon G Ohwaki K Ohyama T Oishi S Oka Y Okada A Olbrich F Olivera-Pastor P Reis A H Rentschler TI Reynes A Rice D A Rigden J S 337,449 Riley F L Rio C d Jolivet J P Lecante P McMurdo J Olivier-Fourcade J Riou.A Jones J R 305,911 Jones R H Leclercq D Le Cras F McSherry I Mehta P G Omenat A Onakhi C Risbud S H Rives V Joswg W Joubert J-C Juan A Judeinstein P Jumas J-C Jungnickel G Kaczmarek J Kaczorowski D Kadokawa J-I Lecuire J-M Lee C K Lee C Y Lee E Lee G R Lee M Le Flem G Lehtinen T Lemaire M Meinhold R H Melnitchenko A Menges B Mercey B Merle-Mejean T Michel C Miller J S Minami T Minceva-Sukarova B Orpen G A Orti E Ostrovski D Otterstedt J-E Ouchi S Ouyang J-m Pac C Pagura C Panda P K Roca S Rodnguez J Rodriguez M L Rodriguez-Castellon E Rohl A L Rohs S Rojas R ROJOT Roncali J Kaenyama K Kagawa S KahnO Lequan M Lequan R M Le Quesne J P Misawa M Mitchell G R Mitov I G Pang W Paprotny J Parent C Ros M B Rosseinsky M J Kajinami A Kakkar A K Lerner M M Leskela M Mittler-Neher S Miura Park J W Parker M J Roy R Ruiz-Amil A Kakudate Y Leskela T Miura Y Paronen M Ruiz-Conde A Kalfat R Kamath P V Kanamura K Lewis D W Lezama L M 1’Hentier P Miyachi K Miyasaka H Miyata F Partndge R D Paschke R Peacock R D Ruiz-Salvador A R Russell D A Ruiz-Hitzky E Tatam R P Uddin M A Williams G.Saadoune I Sironi A Sadaoka Y Skakle J M S Taylor R Uddin R Willis M R UenoT Wilson R C 1871Sadashiva B K Skjerhe K P Teare G C Sadun C Slade R C T Teki Y Uhl M Winfield J M SaeedT SmartL E ten Elshof J E Ulagappan N Withers R L Saito K Smeulders J B A F Tendeloo G V Ulibarn M A Wlodarczyk P Saito Y Smith I K Teraoka Y Urbano F J Wolska E Teunis C J Urbanova M Wolski W 1701Sakamoto M Smith J R Sakata Y Smith M E 337.Thatcher J H Ushitani Y WongG K Thiebaut B Uzunova E L Woolley M 375Salvado M A Smith P C Salvador S Smith W. Thompson D P Vaidhyanathan B Wnght A J Thompson J G Vahg M Wnght P J 1639Samoylenkov S V Smrcok L Sanchez C Soraru G D. Thompson N J Valli L Wnght P V 947Thompson R W van der Put P J J M Wu Y 1391Sanchez Escnbano V Southern J C Sanchez L Stefanis A De Tirado J L van de Velde G M H Wybourne M N 1249Toda K van Dijk M Xia W S 1493Sanchez-Soto P J Steuernagel S Tomas F Vannier R-N Xu R Sanchis M J Stoev M Sanders G M Stradling E P Tomkinson J Vansant E F Tomlinson A A G Varadaraju U V Yamamoto H SanjurJo J A Strobe1 P Sano T Su Q Vaughan White GI Yamamoto N Suarez M Topfer J Vaughey J T Yamamoto T Santos M Subbanna G N Torell L Vente J F Yan M Sasaki S Subramanian M A Toriumi M Verdu M Yan Q Sastre G Subrt J Sat0.M Sudholter E J R Torkkeli M Viau G Yanagmoto H Torncrona A Vijayaknshnan V Yao J Sauer C Torres Martinez Vlll v Yao T Sawada Y Sugahara Y L M Villesuzanne A Yao T-M Sayle D C Sugyama S Tovar S T Vioux A Yasukawa A Scheler U SunY Toyne K J Vitek J Yatabe T.Schnelle W Sundaresan A Tran V H Vogt T Yip B-C Schoonman J Sundholm F Traversa E Volpe P Yonehara H Schouten P G Sundholm G Treacher K E von Minden M Yonemura T 1865Schulz E Sung K Treadwell D R Wait S T Yonezawa S 795Sdoukos A T Suzuki H Tredgold R H Waldner K F Yoshino H 501Segal N Suzuki T Tremayne M Walker T W You F 1633Segre U Suzuki Y-1 Tretyakov Y D Wallart F YOU X-Z 1633Seifert G Szajda w Trindade T Walton R I YuA C 1493Sekine T Szepvolgyi J Troc R Wang S Yue Y Senmaa R Szydiowska J Trombe J-C Warman J M Zarrouk H 1673Sermon P A Tagliatesta P Tronc E Watanabe J Zeng H C 435Serrano J L Tai Z Truffa E Watanabe Zhang B 639.Seshadn R Takahashi M Tschierske C Watts J F Sheldon T J Takanishi Y Weller M T Zhang L Shernngton D C Takashima M Tsodkov M V West A R Zhang P Shibata K Takeda H Tsuchimon M Zhao X S Shimada S Takeda M Tsuji M Whale E A Zhong Q Shinton S Takehara Z-I Tsukahara Y White W B Zhou H Shirai Y Takezoe H Tsutsumi A Whitfield H J Zhou X-F Shirakawa Y Takiff L Tuffin R P Widany J Zhuang H Shirota Y Tamaki S Tundo P Widernik T Zimmer B Shitara Y Tamaura Y Tunega D Wiersema G S Zissi S Silvert P-Y Tanaka K Tunger H-W Wignacourt J P Zou Y Simonin L Tanaka M Tunney J J Williams D E ZUOJ-L Singh N Tang W Turner S S Zyss J Absorbance Optochemical HCl gas detection based on tetraphenylporphine dispersed in ethylcellulose Acid-base hydrolysis Simple aad-base hydrolytic chemistry approach to new matenals for second-order non-linear optics Adamantane Structure of a novel form of carbon dehydropolycondensed adamantane? Adhesive joint failure Interfacial chemistry of adhesive joint failure an investigation by small area XPS imaging XPS and TOF-SIMS Adsorption Adsorption of polycations on clays an zn situ study using 13,Cs solution-phase NMR Synthesis and characterization of a novel layered titanium silicate JDF-L1 Aerogel Surface reactivity and bulk properties of ZrO Part -Thermochemistry of ZrO Y,O,-ZrO and K-ZrO aerogels in and H.Surface reactivity and bulk properties of ZrO Part -Importance of homogeneity in the stabilisation of high surface area Ce0,-ZrO aerogels AI,O,-Sic mixture Carbothermal reduction of sillimanite Alkali-metal fulleride . New preparation of superconducting alkali-metal fullendes utilizing monomethylamine as solvent Alkaline-earth-metal sulfide Oxidation of alkaline-earth-metal sulfide powders and thin films Alk yldiamine Calorimetric study of intercalation of n-alkyldiamines into a-titanium hydrogenphosphate Alumina Alumina purification by carbothermal reduction Alumina te The structures of strontium tellunte and strontium tellunde aluminate sodalites studied by powder neutron diffraction EXAFS IR and MAS NMR spectroscopies Aluminium Keggin ion Intercalation ability of hydrolysed aluminium species in n-alkylmonoamine a-zirconium phosphate compounds Aluminium-matrix composite Consumption of Sic whiskers by the A1-Sic reaction in aluminium- matnx Sic whisker composites Aluminium nitride Preparation of AIN from poly(ethy1iminoalane) ma pyrolysis FTIR analysis of the surface of nanostructured aluminium nitride powder prepared via chemical synthesis Aluminium oxide Precipitation of finely divided A1,03 powders by a molten salt method Aluminol surface Chemically modified kaolinite Grafting of methoxy groups on the interlamellar aluminol surface of kaolinite Aluminophosphate Synthesis and characterization of a novel microporous aluminophosphate AlP0,-JDF (2AlPO -HOCH,CH,NH,) from alcohol systems The structure of the calcined aluminophosphate ALP0,-5 determined by high-resolution X-ray and neutron powder diffraction Aluminosilicate Thermal reactions of alkali-leached aluminosilicates studied by XRD and solid-state 27Al 29S1 and MAS NMR Processable aluminosilicate alkoxide precursors from metal oxides and hydroxides.The oxide one-pot synthesis process Nucleation and crystal growth of analcime from clear aluminosilicate solutions Aminated alkoxide Coordination environment of copper(1r) during the sol-gel process of an aminated alkoxide Aminosilane Simple acid-base hydrolytic chemistry approach to new materials for second-order non-linear optics Amphiphile Reorganisation of layer structures formed from amphiphilic molecules. Preparation and characterization of Langmuir-Blodgett films of N-hexadecyl-8-hydroxy-2-quinolinecarboxamideand its lanthanum complex Synthesis and charactenzation of inorganic gels in a lyotropic liquid crystal medium Part -Synthesis of silica gels in lyotropic crystal phases obtained from cationic surfactants Amphitropic polymer Examples of amphitropic polymers monolayer film Langmuir- Blodgett film and liquid-crystalline properties of some polymenc amphiphiles containing cholestanol moieties and those of some closely related non-polymeric amphiphiles 15.Analcime Nucleation and crystal growth of analcime from clear aluminosilicate solutions Anatase A water-resistant precursor in a wet process for T10 thin film formation Preparation and charactenzation of Au-dispersed T10 thin films by a liquid-phase deposition method Antiferroelectricity Thresholdless antiferroelectricity in liquid crystals and its application to displays Stability of the antiferroelectric phase in dimeric liquid crystals having two chiral centres with CF or CH groups evaluation of conformational and electnc interactions Electroclinic and antiferroelectnc properties of (R)-(-)-nonan-3-ylFerroelectric and antiferroelectric liquid crystalline phases in some pyridine carboxylic acid denvatives Antiferromagnetism Metamagnetism in EuPdIn and EuAuIn Synthesis crystal structure and spectroscopic properties of the NH,NiPO nH,O (n= 1,6) compounds magnetic behaviour of the monohydrated phase Structure refinement magnetic susceptibility electncal conductivity and europium- Mossbauer spectroscopy of EuNiIn Antifriction additive Synthesis of long chain alkyl and chloroalkyl esters of perfluorosalicylic acid new potential high temperature antifriction additives for advanced motor oils Antimony doping EELS and photoemission study of antimony-doped Cd,SnO ceramics Low-temperature stabilisation of tetragonal zirconia by antimony Apatite structure Crystal structure and magnetic properties of Ba,,(MnFeF,,-,Cl,),F,Cl,- (x=O 85) Structural relationships with the apatite-type structure Atomic force microscopy Ordering and manipulation of MoS platelets on differently charged micas by atomic force microscopy .Atomic layer epitaxy Growth of gallium oxide thin films from gallium acetylacetonate by atomic layer epitaxy Augmented spherical wave The electronic and magnetic structures of stoichiometric SrCo03 ASW calculations V Aurivillius phase From Bi4V201 to Bi,V,O,O the Vv-V1v transformation in the Aunvillius-type framework Comparison of X-ray patterns and Raman spectra of n =2 and Aurivillius phases by principal component analysis Autocombustion Chemical synthesis of barium zirconate titanate powder by an autocombustion technique Azide Laser photolytic studies of sensitizers for negative photoresists Band structure A density-functional based tight-binding approach to III-V semiconductor clusters Theoretical determination of the molecular and solid-state electronic structures of phthalocyanine and largely extended phthalocyanine macrocycles Barium cerate Unit-cell symmetnes and Raman spectra of calaum- and neodymium-doped barium cerate proton-conducting ceramic electrolytes Barium hexaaluminate Single-crystal X-ray structure analysis of Mn-substituted banum hexaaluminates as-grown and after reduction Barium-substituted copper oxyhalide Stabilisation of Ba,CuO,Cl with the K2NiF4 structure by chemical substitution Barium tetratitanate Preparation of BaTi,O by a sol-gel method and its photocatalytic activity for water decomposition Barium zirconate titanate Chemical synthesis of barium zirconate titanate powder by an autocombustion technique Battery Sol-gel-denved vanadium and titanium oxides as cathode materials in high-temperature lithium polymer-electrolyte cells B-C-N solid solution Synthesis and characterization of a shock-synthesized cubic B-C-N solid solution of composition BC ,N Bis(ether anhydride) Nitrodisplacement reactions and the synthesis of bis(ether anhydride)s from dihydroxynaphthalenes Bismuth Influence of crystal structure on the luminescence properties of bismuth(m) europium(II1) and dysprosium(II1) in Y,SiO Bismuth telluride Synthesis properties and performances of electrodeposited bismuth tellunde films Bismuth vanadium oxide From Bi4V2011 to Bi4V2010 the VV-VIv transformation in the Aurivillius-type framework Bis( perfluorophenyl azide) Evaluation of bis( perfluorophenyl azide)s as cross-linkers for a soluble polyimide Bithiophene Boron derivatives containing a bithiophene bndge as new materials for non-linear optics Boehmite.Dehydroxylation sequences of gibbsite and boehmite study of differences between soak and flash calcination and of particle- size effects Borohydride reduction Generation of magnetic metal particles in zeolite by borohydride reduction at ambient temperature Borowaluminium 0x0 chloride On the crystallisation and nature of the microporous boron- aluminium 0x0 chlonde BAC( lo) Boron hyperpolarizability Boron derivatives containing a bithiophene bndge as new materials for non-linear optics Boron nitride .Investigation of the stability of the hexagonal-cubic boron nitnde prism interface Cadmium oxide Oriented cadmium oxide thin solid films Cadmium oxide-antimony oxide system Vapour sensing properties of a cadmium oxide-antimony oxide system ceramic Cd2Sb206 v1 Cadmium selenide Synthesis of CdS and CdSe nanoparticles by thermolysis of diethyldithio- or diethyldiseleno-carbamates of cadmium Cadmium sulfide Synthesis of CdS and CdSe nanoparticles by thermolysis of diethyldithio- or diethyldiseleno-carbamates of cadmium XPS and XRD study of photoconductive CdS films obtained by a chemical bath deposition process Effect of pyridine upon gas-phase reactions between H,S and Me,Cd control of nanoparticle growth Processing and optical properties of spin-coated polystyrene films containing CdS nanoparticles Synthesis and charactenzation of II-VE semiconductor nanoparticulates by the reaction of a metal alkyl polymer adduct with hydrogen sulfide Caesium-133 Adsorption of polycations on clays an in situ study using 133Cs solution-phase NMR Calcination Dehydroxylation sequences of gbbsite and boehmite study of differences between soak and flash calcination and of particle- size effects Calcined aluminophosphate The structure of the calcined aluminophosphate ALP04-5 determined by high-resolution X-ray and neutron powder diffraction Calcium hydroxyapatite Surface and bulk properties catalytic activities and selectivities in methane oxidation on near-stoichiometric calcium hydroxyapatites Calcium oxide-zinc oxide Photoluminescence study of (CaO) -,(ZnO) powder solids in air Calorimetry Consumption of Sic whiskers by the A1-Sic reaction in aluminium- matrix Sic whisker composites Calorimetnc study of intercalation of n-alkyldiamines into a-titanium hydrogenphosphate Carbohydrates Structural variation of liquid crystalline tnoxadecalins Carbon-bearing nickel (11) ferrite A carbon-bearing nickel(I1) ferrite a tailor-made solid reactant for two-step thermochemical water splitting at 300" C Carbon fibre A model of duplex structure for short vapour-grown carbon fibres Carbonitridation Carbothermal reduction of sillimanite Carbon structure Structure of a novel form of carbon dehydropolycondensed adamantane? Structure of carbon produced by hydrothermal treatment of p-Sic powder Carbonyl sulfide Carbonyl sulfide (OCS) as a sulfur-containing precursor in MOCVD a study of mixtures of Me,Cd and OCS in the gas and solid phases and their use in MOCVD Carbothermal reduction Alumina purification by carbothermal reduction Modified carbothermal reduction for the synthesis of ultrafine particle tungsten compounds dispersed in a microporous carbon matrix Carbothermal reduction of sillimanite Carbothermal reductiownitridation Volatile products formed by carboreduction and nitridation of clay mixtures with silica and elemental silicon Catalyst characterization Charactenzation of RUM-SiO catalysts A comparative study before and after CO hydrogenation reaction .Catalytic properties Synthesis and catalytic properties of perovskite-related phases in the La-Sr-Co-Cu-Ru-0 system Magnesium- and iron-doped chromium fluonde/hydroxyfluonde synthesis charactenzation and catalytic activity Cathodic disbondment Interfacial chemistry of adhesive joint failure an investigation by small area XPS imaging XPS and TOF-SIMS Cation exchange Protonation and olation of 2,2 -bipyndyl and 1,lO-phenanthroline in y-titanium phosphate dihydrate Organometallic cation-exchanged phyllosilicates vanable- temperature 57Fe Mossbauer spectroscopic and related studies of the adsorption of dimethylaminomethylferrocene on clays and pillared clays Cationic framework On the crystallisation and nature of the microporous boron- aluminium 0x0 chlonde BAC( lo) Cationic surfactant.The reversible extraction of the hexamminecobalt(II1) cation by kanemite (NaHSi,O -3H,O) enhanced extraction in the presence of a cationic surfactant Ceramic Structural and electronic properties of the compounds Ba41r,MOlz (M =Li Na Mg Y Lu Zr and Ce) Vapour sensing properties of a cadmum omde-antimony oxide system ceramic Cd,Sb206 Oxygen-nitrogen ordenng in yttnum nitrogen melilite Precipitation of finely divided Al,03 powders by a molten salt method EELS and photoemission study of antimony-doped Cd,Sn04 ceramics Ceramic electrolyte Unit-cell symmetnes and Raman spectra of calcium- and neodymium-doped banum cerate proton-conducting ceramic electrolytes Ceria Preparation of ceria-coated composite silica particles Surface reactivity and bulk properties of ZrO Part -Importance of homogeneity in the stabilisation of high surface area Ce0,-ZrO aerogels Charge transfer Charge-transfer complex and radical cation salt of a new donor EDT-TTFCl unique conductivities and crystal structures Structure dielectnc relaxation and electncal conductivity of 2,3,7,8- tetramethoxy-chalcogenanthrene-2,3-dichloro-5,6-dicyano-benzoquinone charge-transfer complexes Structure of two polymorphs of the TTF-TCNE charge-transfer complex and the degree of ionicity Charactenzation of novel TCNQ and TCNE and salts of the tetrakis(dimethyam1no)ethylene dication C((CH3)zN) zC-C(N(CH3 )z 1,I2+ 1627Charge transport Preparation voltammetry coulometry and electrochemical quartz crystal gravimetry of [Os( bipy),( PVPS),ClRu(edta)] redox polymers Investigations on the charge transport in LaMnO at low temperatures Chemical bath deposition XPS and XRD study of photoconductive CdS films obtained by a chemical bath deposition process Oriented cadmium oxide thin solid films Speclation and the nature of ZnO thin films from chemical bath deposition Chemical doping Stabilisation of Ba,CuO,Cl with the K,NiF4 structure by chemical substitution Chemical model Chemical models for the cure of epoxy resins the influence of hydrogen bonding Chemical vapour deposition Laser-induced chemical vapour deposition of Si/C/H matenals from monoorganylsilanes .IR laser-induced decomposition of 2-chloroethenylsilane for chemical vapour deposition of Si/C phases Chemical vapour deposition of tantalum silicide thin films from difluorosilylene and tantalum halides Chemomechanical polishing Chemomechanical polishing of silica and silicon by fluonde- and oxide-based reagents identification of a reaction intermediate Chimie douce Preparation by a ‘chzmie douce’ route and characterization of LiNi,Mn -zO (0 <z <1) cathode matenals Chirality Structural vanation of liquid crystalline tnoxadecalins Stability of the antiferroelectnc phase in dimenc liquid crystals having two chiral centres with CF or CH groups evaluation of conformational and electric interactions Highly twisting enantiomenc radial multiyne dopants for discotic liquid-crystalline systems Thermal and optical properties of chiral twin liquid crystalline bis(cholestery1) alkanedioates Ferroelectnc and antiferroelectnc liquid crystalline phases in some pyndine carboxylic acid derivatives Chlorine Gas-sensitive resistors surface interaction of chlonne with semiconducting oxides C hloroethen ylsilane IR laser-induced decomposition of 2-chloroethenylsilane for chemical vapour deposition of Si/C phases Chromium aluminophosphate Synthesis and precise charactenzation of large single crystals of as- synthesized CrAPO-5 H ,[Cr 08A111 62P12048]F1 ,-1 6TEA Chromium hydroxyfluoride Magnesium- and iron-doped chromium fluoride/hydroxyfluoride synthesis charactenzation and catalytic activity Chromium oxide New porous Ga/Cr mixed oxide pillared a-zirconium phosphate materials Mesostructured lamellar chromium oxide Chromium sulfide Magnetic properties of ternary chromium sulfides V,Cr -rS4 (Odx<lO) Citrate-nitrate gel Chemical synthesis of barium zirconate titanate powder by an autocombustion technique Clay Adsorption of polycations on clays an in situ study using 13,Cs solution-phase NMR Volatile products formed by carboreduction and nitridation of clay mixtures with silica and elemental silicon Copper ion binding to N-phenylphthalamic acid studied by 13C nuclear magnetic resonance and electron paramagnetic resonance model interaction of polyamic acid with copper Coating.Preparation of ceria-coated composite silica particles Cobalt gallium phosphate Solvothermal synthesis and structural characterisation of the first ammonium cobalt gallium phosphate hydrate NH~[C~G~ZP~~~Z(HZO)ZI,CO hydrogenation Characterization of RuM*SiO catalysts A comparative study before and after CO hydrogenation reaction Colloid Preparation of uniform zinc oxide colloids by controlled double-jet precipitation Preparation of colloidal silver dispersions by the polyol process Part 1-Synthesis and characterization Columnar liquid crystals Self-assembled monolayers of phthalocyanine derivatives on glass and silicon Complexation Liquid-crystalline rod-coil polymers based on poly(ethy1ene oxide)s and the influence of the complexation of LiCF,SO on the liquid-crystalline assembly Computer modelling Computer modelling of V,O surface structures crystal morphology and ethene sorption Conducting polymer .Synthesis and gas sensing properties of poly [tetra(pyrro1-1-y1)-silane] Synthesis and characterization of organic conductors derived from ( 1H-pyrrol-3-y1)acetic acid esters Structure and properties of sulfonated poly [(vinylidene fluoride)- g-styrene] porous membranes Conductivity Charge-transfer complex and radical cation salt of a new donor EDT-TTFCl unique conductivities and crystal structures Structure dielectric relaxation and electncal conductivity of 2,3,7,8- tetramethoxy-chalcogenanthrene-2,3-dichloro-5,6-dicyano-benzoquinone charge-transfer complexes Preparation and charactensation of conductive Langmuir-Blodgett films of a tetrabutylammonium-Ni(dmit) complex Study of the order-disorder transition in yttria-stabilised zirconia by neutron diffraction Conductivities of some PEO complexes of lithium and sodium salts with aromatic and heterocyclic anions v11 Poly [oxymethylene-oligo(oxyethylene)] network electrolytes Amorphous and crystalline copper sulfides CuS Ionic conductivity of SrO-Ta,O and SrO-La,O,-Ta,O compounds Selectivity and composition dependence of response of gas-sensitive resistors Characterisation and properties of the non-stoichiometric perovskite Ca,Fe,-,Nb,O (0 45<x<O 65) Conjugated polymer The synthesis of an electronically asymmetric substituted poly (arylenevinylene) poly {2-(2'-ethylhexyloxy)-5-[(E)-4'-nitrostyry1)- 1,4-phenylenevinylene} Conjugated system Oligo(furan-2,5-diylvinylene)sas n-conjugating spacers in linearly extended hybrid tetrathiafulvalene analogues Coordination polymer Spin-crossover behaviour of the coordination polymer Fel'(C,H,N),Nil'(CN) Copol yesterifica tion Linear precursors of liquid crystalline thermosets Copolymer Examples of amphitropic polymers monolayer film Langmuir- Blodgett film and liquid-crystalline properties of some polyrnenc amphiphiles containing cholestanol moieties and those of some closely related non-polymeric amphiphiles CopperThe solid solution BaLi -,Cu,PO (xd0 5) an example of Cuf single-ion luminescence in oxide insulators Paramagnetic liquid-crystal side-chain polyacrylates containing Schiff-base copper(i1) complexes Copper ion binding to N-phenylphthalamic acid studied by 13C nuclear magnetic resonance and electron paramagnetic resonance model interaction of polyamic acid with copper Copper complex Mesogenic properties of novel enamino ketone ligands and their copper(i1) complexes Copper extraction Lithium intercalation and copper extraction in spinel sulfides of general formula Cu,MSn,S (M =Mn Fe Co Ni) Copper oxycarbonate microstructural study Microstructure of superconducting copper oxycarbonate thin films of the Ba-Ca-Cu-C-0 system Copper sulfide Amorphous and crystalline copper sulfides CuS Coumarin laser dye Enhanced fluorescence of coumarin laser dye in the restricted geometry of a porous nanocomposite Cr APO-5 Synthesis and precise charactenzation of large single crystals of as- synthesized CrAPO-5 H [Cr osAlll 62P12048]F1,* 6TEA Cross-linked inorganic polymer linked polysiloxanes prepared from polymethylhydrosiloxane Cross-linking reaction Preparation and properties of epoxidized natural rubber/poly(E- caprolactone) self-vulcanizable blends Crystal growth Monodisperse iron-based particles precipitation in liquid polyols Growth of emerald crystals by evaporation of a K,O-MOO flux,.Nucleation and crystal growth of analcime from clear aluminosilicate solutions Cry stallisation On the crystallisation and nature of the microporous boron- aluminium 0x0 chloride BAC( lo) Crystal morphology Computer modelling of V,O surface structures crystal morphology and ethene sorption Crystal orbital overlap population The electronic and magnetic structures of stoichiometnc SrCoO ASW calculations Crystal structure Synthesis crystal structure and magnetic properties of Ln -,Sr,NiO solid solutions (Ln =La Nd Sm and Gd Hydrothermal syntheses and crystal structures of new layered tungsten(v1) methylphosphonates M,( WO,),PO,CH (M=NH Rb CS) .Synthesis polymorphic characterization and structural comparisons of the non-linear optically active and inactive forms of polymorphs of 3-(nitroanilino)cycloalk-2-en-l-ones,123 Synthesis and crystal structure of zeolite W resembling the mineral merlinoite Synthesis crystal structure and spectroscopic properties of the NH,NiPO nH,O (n=1,6) compounds magnetic behaviour of the monohydrated phase Single-crystal X-ray structure analysis of Mn-substituted banum hexaaluminates as-grown and after reduction Charge-transfer complex and radical cation salt of a new donor EDT-TTFC12 unique conductivities and crystal structures Synthesis and crystal structures of two metal phosphonates M (H03PC6H5) (M =Ba Pb) LiSb(edta)(H,O) a convenient precursor to LiSbS and LiSbO Synthesis and structure determination of new layered perovskite compounds ALaTa,O and ACa,Ta301 (A =Rb Li) Synthesis and crystal structure of ULM-16 a new open-framework fluorinated gallium phosphate with 16-nng channels Ga,(P04),F2 -1 5NC6H14-05H20*0 5H30 Solution of an organic crystal structure from X-ray powder diffraction data by a generalized rigid-body Monte Carlo method crystal structure determination of l-methylfluorene Charactenzation of novel TCNQ and TCNE and salts of the tetrakis(dimethyam1no)ethylene dication C{(CH3)2Nl,c-C {N(CH3)2 +3 Crystal structure and magnetic properties of Balo(MnFeFll ~Cl,)3FxC12-x (x=O 85) Structural relationships with the apatite-type structure Transition-metal stannides with high tin content Os,Sn RhSn RhSn and IrSn The crystal structure of Li3Sb04 Cuprate superconductor Thermoanalytical study of oxoanion-substituted cuprate superconductors Curie-Weiss behaviour Magnetic electrical and "'Eu Mossbaucr properties of EuPtGe Curing Effect of complexation with copper(I1) on cured neat resin properties of a commercial epoxy resin using modified imidazole curing agents Chemical models for the cure of epoxy resins the influence of hydrogen bonding Cyanine dye Synthesis and physical performance of indole and benzimidazole cyanine dyes Cyclic oligosiloxane Dielectric relaxation in four cyclic liquid-crystalline oligosiloxanes with different ring size and spacer length Cyclic voltammetry Characterization of novel TCNQ and TCNE and salts of the tetrakis(dimethyam1no)ethylenedication C((CH3 )2Nl 2C-C{N(CH3)2 1,I2+ C yclohexenone Synthesis and mesogenic properties of 3,6-disubstituted cyclohex-2- en-l-ones C yclotriveratrylene The influence of heteroatoms and branchings on the liquid- crystalline properties of cyclotnveratrylene derivatives Decamethylmetallocenium Two-dimensional molecular-based ferrimagnets incorporating decamethylmetallocenium cations Defect ferrite Hydrothermal conversion of amorphous NiFe,-,Al,(OH) into crystalline phases Dehydration Dehydration-rehydration in magnesium vermiculite conversion from two-one and one-two water layer hydration states through the formation of interstratified phases Dehydropolycondensed adamantane Structure of a novel form of carbon dehydropolycondensed adamantane? Vlll Dehydroxylation Doping Dehydroxylation sequences of gbbsite and boehmite study of Iron-doped zirconium silicate Part -The location of iron differences between soak and flash calcination and of particle- Unit-cell symmetnes and Raman spectra of calcium- and size effects neodymium-doped banum cerate proton-conducting ceramic Densification electrolytes Composition and microstructure of nanosized amorphous and Highly twisting enantiomenc radial multiyne dopants for discotic crystalline silicon nitnde powders before during and after liquid-crystalline systems densification Magnesium- and iron-doped chromium fluoride/hydroxyfluonde Density-functional theory synthesis characterization and catalytic activity 1731.A density-functional based tight-binding approach to III-V Double-jet precipitation semiconductor clusters Preparation of uniform zinc oxide colloids by controlled double-jet Stability of silicon carbide structures precipitation from clusters to solid surfaces DRIFT spectroscopy The electronic and magnetic structures of stoichiometric SrCoO Synthesis and charactenzation of vanous MgO and related systems ASW calculations Density functional-tight binding scheme DyeStability of silicon carbide structures Controlling the structure of transparent Langmuir-Blodgett films from clusters to solid surfaces for nonlinear optical applications Deoxygenation Synthesis and physical performance of indole and benzimidazole Microwave-assisted selective deoxygenation of layer- and chain- cyanine dyes containing oxides ‘Molecular zips’ evidence of the interdigitation of layers in Depth profiling Langmuir-Blodgett films of an optically non-linear dye and a Investigation of the formation of Ru0,-based mixed oxide coatings compatible spacer by secondary ion mass spectrometry Structure of rhodanine cyanine dyes spectroscopy and performance Synthesis of polymers containing 9,10-diacetoxyanthracene-2,6-diyl Dysprosium moieties via a precursor polymer approach Influence of crystal structure on the luminescence properties of Diazidofluorene bismuth(m) europium(n1) and dysprosium(m) in Y,SiO Laser photolytic studies of sensitizers for negative photoresists 2,7- EELS diazidofluorene in poly(methy1 methacrylate) films EELS and photoemission study of antimony-doped Cd,SnO Dicadmium stannate ceramics EELS and photoemission study of antimony-doped Cd,SnO Elastomer .ceramics Preparation and properties of epoxidized natural rubber/poly(e- Dielectric relaxation spectroscopy caprolactone) self-vulcanizable blends Molecular motions near the glass transition in diethylene glycol Electrical conductivity bis(ally1 carbonate) as studied by dielectnc relaxation Electrochemical doping of a-ethyl-disubstituted oligothiophenes and spectroscopy electrical conductivities of the resulting radical-cation salts Supermolecular alignment in a liquid crystal-polymer gel as studied High-temperature electncal conductivity of FeTiO and ilmenite optically and by dielectric relaxation spectroscopy Structural relaxation and crystallization of semiconducting vanadate Dielectnc relaxation in four cyclic liquid-crystalline oligosiloxanes glass accompanying a jump of the electncal conductivity with different ring size and spacer length Electrical properties Diethylene glycol bis(ally1 carbonate) Preparation and electncal properties of KCa -xLa,Nb30 Molecular motions near the glass transition in diethylene glycol Evidence of new layered cuprates in the Hg-A-Gd-Cu-0 system (A =Ba Sr) bis(ally1 carbonate) as studied by dielectric relaxation Electrical resistivity spectroscopy Differential scanning calorimetry Crystal structure and physical properties of UAuSi and UAu Thermotropic phase transitions in 5,15-bis( 4-alkoxypheny1)- Electrical switching octaalkylporphyrins Electrical switching in V02 sol-gel films Dih ydrox ynaphthalene Electrocatalysis Nitrodisplacement reactions and the synthesis of bis(ether Investigation of the formation of Ru0,-based mixed oxide coatings by secondary ion mass spectrometry anhydnde)s from dihydroxynaphthalenes ElectroceramicSynthesis and properties of poly(ether imide)s derived from Preparation and characterization of perovskite-type dihydroxynaphthalenes Ln’xLn”l -.Coo3 for electroceramic applications Dimer Electrochemical quartz crystal microbalance Thermal and optical properties of chiral twin liquid crystalline Electrochemical quartz crystal microbalance studies of partially bis(cholestery1) alkanedioates oxidized tetracyanoplatinum salts Dimethylaminometh ylferrocene Electrochemical synthesis Organometallic cation-exchanged phyllosilicates variable- Electrochemical syntheses of two doped forms of poly(su1fur temperature 57Fe Mossbauer spectroscopic and nitride) { [SN] [AsF,]} and { [SN] [AsF,]} 1161related studies of the adsorption of Electrochemical synthesis and thermal decomposition of zirconia dimethylaminomethylferroceneon clays and pillared clays gels containing vanous metal ions Dimethyl cadmium ElectrochemistryCarbonyl sulfide (OCS) as a sulfur-containing precursor in Electrochemical doping of a-ethyl-disubstituted oligothiophenes and MOCVD a study of mixtures of Me,Cd and OCS in the gas electrical conductivities of the resulting radical-cation salts and solid phases and their use in MOCVD Studies on the electrochemical deposition of niobium oxide Dispersed gold particles LiNi -yCO,,O positive electrode materials relationships between Preparation and charactenzation of Au-dispersed T10 thin films by the structure physical properties and electrochemical a liquid-phase deposition method behaviour Dithiobispyridine Photo-active and electro-active protein films prepared by Intercalation of 2- 4-sulfanylpyridine 2,2’- and 4,4 -reconstitution with metalloporphyrins self-assembled on gold dithiobispyridine into VOPO and gel-V,O interlayer spaces Divalent metal phosphonate films of a tetrabutylammonium-Ni(dmit) complex Structure of Zn(O,PC,H,CO,H) 5C6H,NH2 and XANES-EXAFS Preparation voltammetry coulometry and electrochemical quartz study of the intercalation of amines into Zn(0,PR) H,O zinc crystal gravimetry of [Os(bipy),( PVPS),ClRu(edta)] redox alkylphosphonates polymers Optical waveguide fabncation using a polymenc azine containing Electrochemical quartz crystal microbalance studies of partially the 3-dodecylthiophene moiety oxidized tetracyanoplatinum salts ix Electrode material LiNi -yC0y02 positive electrode matenals relationships between the structure physical properties and electrochemical behaviour MVOs (M =Nb Ta) mixed oxides sol-gel synthesis structural and thermal charactenzation and electrochemical Li' insertion Electrodeposition Electrodeposition of thin-film rare-earth-metal oxocuprates Studies on the electrochemical deposition of niobium oxlde Synthesis properties and performances of electrodeposited bismuth telluride films .Electrochemical syntheses of two doped forms of poly(su1fur nitride) {CSNIsCAsF,I~ and {CSNl,,CA~F,I~x Elec troluminescence Improved electroluminescence performance of poly (3-alkylthiophenes) having a high head-to-tail (HT) ratio Electronic asymmetry The synthesis of an electronically asymmetnc substituted poly(arylenevinylene) poly {2-(2'-ethylhexyloxy)-5-[(E)-4'-nitrostyry1)- 1,4-phenylenevinylene} Electronic properties Structural and electronic properties of the compounds Ba,Ir,MO12 (M=Li Na Mg Y Lu Zr and Ce) Synthesis reactivity structure and electronic properties of "(CH,),] c60-1 5thf fullendes with simple hexagonal packing Electronic structure Theoretical determination of the molecular and solid-state electronic structures of phthalocyanine and largely extended phthalocyanine macrocycles The electronic and magnetic structures of stoichiometnc SrCoO ASW calculations Electron paramagnetic resonance Copper ion binding to N-phenylphthalamic acid studied by I3C nuclear magnetic resonance and electron paramagnetic resonance model interaction of polyamic acid with copper Electron transport N-(2,4,7-Trinitrofluorenylidene)anilines-new electron transport materials in positive charge electrophotography Electrophilic aromatic substitution .Chemical modification of monolithic poly(styrene4vinylbenzene) PolyHIPE@ materials Electrorheological properties Electrorheologcal properties of polypyrrole prepared by the action of mineral acids on pyrrole Electrostatic spray deposition Morphology control of thin LiCoO films fabricated using the electrostatic spray deposition (ESD) technique Emerald crystal Growth of emerald crystals by evaporation of a K,O-MOO flux Enamino ketone Mesogenic properties of novel enamino ketone ligands and their copper(n) complexes Energy dispersive X-ray diffraction Structural study by energy dispersive X-ray diffraction of amorphous mixed hydroxycarbonates containing Co Cu Zn Al Enhanced extraction The reversible extraction of the hexamminecobalt(II1) cation by kanemite (NaHSi,O -3H@) enhanced extraction in the presence of a cationic surfactant Epoxidized natural rubber Preparation and properties of epoxidized natural rubber/poly(c- caprolactone) self-vulcanuable blends Epoxy resin Effect of complexation with copper(r1) on cured neat resin properties of a commercial epoxy resin using modified imidazole curing agents Chemical models for the cure of epoxy resins the influence of hydrogen bonding EPR spectroscopy Coordination environment of copper@) during the sol-gel process of an aminated alkoxide Optical and EPR spectroscopic studies of silver clusters in Ag,Na-Y zeolite by y-irradiation Ethene sorption Computer modelling of V20s surface structures crystal morphology and ethene sorption X Ethylenediaminetetraacetate complex LiSb(edta)(H,O) a convenient precursor to LiSbS and LiSbO Ethylene glycol Preparation of colloidal silver dispersions by the polyol process Part -Synthesis and charactenzatlon EuNiIn Structure refinement magnetic susceptibility electncal conductivity and europium-151 Mossbauer spectroscopy of EuNiIn Europium Influence of crystal structure on the luminescence properties of bismuth(m) europium(II1) and dysprosium(n1) in Y2S10s Europium-151 Mossbauer spectroscopy Magnetic electrical and "'Eu Mossbauer properties of EuPtGe Structure refinement magnetic susceptibility electncal conductivity and europium-151 Mossbauer spectroscopy of EuNiIn Europium azo compound Second-order non-linear optical properties of Langmuir-Blodgett films of a new azo compound (p-NO,) C6H,N=NC,oH,0(CH,),N(CH3),C18H37Brand its europium complex Europium-bismuth-vanadium oxide Synthesis and structural investigation of the Eu -,Bi,VO scheelite phase X-ray diffraction Raman scattering and Eu3+ luminescence Europium-transition metal-indium intermetallic Metamagnetism in EuPdIn and EuAuIn Europium(m ) luminescence Synthesis and structural investigation of the Eu -,Bi,VO scheelite phase X-ray diffraction Raman scattenng and Eu3+ luminescence EXAFS Surface and bulk properties catalytic activities and selectivities in methane oxidation on near-stoichiometric calcium hydroxyapatites EXAFS-XANES study Structure of Zn(03PC2H,C02H) 5C6H,NHz and XANES-EXAFS study of the intercalation of amines into Zn(0,PR) H,O zinc alkylphosphonates .Feature article.Hybrid organic-inorganic materials a land of multidisciphnarity Thin film formulations of substituted phthalocyanines Ultrasound in matenals chemistry Ferrimagnet Two-dimensional molecular-based fernmagnets incorporating decamethylmetallocenium cations Ferrocene Ferrocene-containing thermotropic liquid crystals laterally connected twins Ferroelectricity Stability of the antiferroelectnc phase in dimeric liquid crystals having two chiral centres with CF or CH groups evaluation of conformational and electnc interactions Distinct ferroelectric smectic liquid crystals consisting of banana shaped achiral molecules Ferroelectric and antiferroelectric liquid crystallme phases in some pyridine carboxylic acid denvatives Influence of the host-guest interactions on the ferroelectnc properties of mononuclear orthopalladated metallomesogen mixtures Ferromagnetism Metamagnetism in EuPdIn and EuAuIn The electronic and magnetic structures of stoichiometnc SrCoO ASW calculations Fibre optic device Z-type Langmuir-Blodgett film structures surface plasmon resonance second harmonic generation and fibre optic devices Film deposition Thermal decomposition of V(NEt,) in an MOCVD reactor a low- temperature route to vanadium carbonitnde coatings Film growth mechanism Thermal decomposition of V(NEt,) in an MOCVD reactor a low-temperature route to vanadium carbonitride coatings Fluorescence Enhanced fluorescence of coumarin laser dye in the restncted geometry of a porous nanocomposite Fluorinated gallophosphate Synthesis and crystal structure of ULM-16 a new open-framework fluonnated gallium phosphate with 16-nng channels Ga4(P04)4F2. 5NC6H14 -0 5H20.0 5H30 Fluorphlogopite-coumarin complex Enhanced fluorescence of coumann laser dye in the restricted geometry of a porous nanocomposite Fourier analysis Dehydration-rehydration in magnesium vermiculite conversion from two-one and one-two water layer hydration states through the formation of interstratified phases FTIR spectroscopy FTIR analysis of the surface of nanostructured aluminium nitnde powder prepared via chemical synthesis Fuel cell Preparation and charactenzation of perovskite-type Ln',Ln'' -,COO for electroceramic applications Fullerene Metal-insulator transition and molecular dynamics in (NH3)K,C6 Fulleride Synthesis reactivity structure and electronic properties of "(CH,),] C6 5thf fullendes with simple hexagonal packing Gallium oxide Growth of gallium oxide thin films from gallium acetylacetonate by atomic layer epitaxy New porous Ga/Cr mixed oxide pillared a-zirconium phosphate materials Gallophosphate Synthesis and crystal structure of ULM-16 a new open-framework fluorinated gallium phosphate with 16-ring channels Ga4( PO4)4FZ -1 5NC6H14 -05H20.0 5H@ Gas chromatography Pyrolysis study of methyl-substituted Sir H containing gels as precursors for oxycarbide glasses by combined thermogravimetry gas chromatographic and mass spectrometric analysis Gas-phase reaction Effect of pyridine upon gas-phase reactions between H,S and Me,Cd control of nanoparticle growth Gas-sensi t ive resistor Gas-sensitive resistors surface interaction of chlonne with semiconducting oxides Selectivity and composition dependence of response of gas-sensitive resistors Selectivity and compositional dependence of response of gas- sensitive resistors Part -Properties of some rutile solid solution compounds Gas sensor .Nitrogen dioxide and volatile sulfide sensing properties of copper zinc and nickel chromite Vapour sensing properties of a cadmium oxide-antimony oxide system ceramic CdzSbZO Synthesis and gas sensing properties of poly [tetra( pyrrol-l- yl)silane] Optochemical HC1 gas detection based on tetraphenylporphine dispersed in ethylcellulose Gel Pyrolysis study of methyl-substituted Sir H containing gels as precursors for oxycarbide glasses by combined thermogravimetry gas chromatographic and mass spectrometric analysis Germanium carbide Thin film deposition of Ge,CyH by radiolysis of GeH,-C,H mixtures Gibbsite Dehydroxylation sequences of gbbsite and boehmite study of differences between soak and flash calcination and of particle- size effects Glass.Preparation and charactensation of high refractive index PbO-TiO,-TeO glass systems Grafting Structure and properties of sulfonated poly [(vinyhdene fluoride)-g-styrene] porous membranes Hafnia Halogen bridge ortho-Palladated metallomesogens the effects of structural modifications on their liquid crystalline behaviour Helical twist Highly twisting enantiomeric radial multiyne dopants for discotic liquid-crystalline systems Hexagonal-cubic interface Investigation of the stability of the hexagonakubic boron nitnde pnsm interface Hexamminecobalt(111) extraction The reversible extraction of the hexamminecobalt(ru) cation by kanemite (NaHSi205 -3H,O) enhanced extraction in the presence of a cationic surfactant High-resolution electron microscopy Microstructure of superconducting copper oxycarbonate thin films of the Ba-Ca-Cu-C-0 system Sheanng mechanism in the Bi-Sr-Cu oxycarbonates HREM study of a new collapsed phase Bi15Sr,9Cu12(C0,)7056 High-resolution X-ray diffraction The structure of the calcined aluminophosphate ALP04-5 determined by high-resolution X-ray and neutron powder diffraction High-temperature superconductor Effect of oxygen partial pressure on the Tl,Ba2Cu0,T12Ba2CaCu,0 transformation Hofmann-type compound Spin-crossover behaviour of the coordination polymer Fe"(C5H5N),Ni"(CN) Hot-pressing Composition and microstructure of nanosized amorphous and crystalline sihcon nitnde powders before during and after densification Hydration Layered structures of hydrated vanadium oxides Part -Single- crystal structure of Rb sV205 and phase changes of rubidium intercalate Hydrogenated germanium carbide Thin film deposition of Ge,CyH by radiolysis of GeH4-C,H8 mixtures Hydrogen bonding A ',Na NMR study of hydrous layered silicates Chemical models for the cure of epoxy resins the influence of hydrogen bonding Molecular design of amphotropic matenals influence of oligooxyethylene groups on the mesogenic properties of calamitic liquid crystals Structure and dynamics of hydrogen bonding guests in urea inclusion compounds Hydrogen chloride Optochemical HCl gas detection based on tetraphenylporphine dispersed in ethylcellulose H ydrotalcite Precursor dependence of the nature and structure of non- stoichiometnc magnesium aluminium vanadates Thermal behaviour of Zn-Cr layered double hydroxides with hydrotalcite-like structures containing carbonate or decavanadate Hydrothermal treatment Structure of carbon produced by hydrothermal treatment of p-Sic powder a-H ydroxide Homogeneous precipitation from solution by urea hydrolysis a novel chemical route to the a-hydroxides of nickel and cobalt Hydrox yapatite Preparation and characterization of magnesiumsalcium hydroxyapatites Ilmenite High-temperature electncal conductivity of FeTiO and ilmenite Imidazole Effect of complexation with copper(1r) on cured neat resin properties of a commercial epoxy resin using modified imidazole cunng agents Impact interaction Formation mechanism of a crystalline Ag,,Pd solid solution by impact ball-matenals interaction Inclusion The structures of strontium tellurite and strontium telluride .aluminate sodalites studied by powder neutron diffraction EXAFS IR and MAS NMR spectroscopies Structure and dynamics of hydrogen bonding guests in urea inclusion compounds xi Infrared spectroscopy Infrared reflection study of cofacially stacked phthalocyanines doped with iodine Insertion compound MVO (M =Nb Ta) mixed oxides sol-gel synthesis structural and thermal charactenzation and electrochemical Li' insertion Intercalation Intercalation ability of hydrolysed aluminium species in n-alkylmonoamine a-zirconium phosphate compounds Protonation and olation of 2,2'-bipyridyl and 1,lO-phenanthroline in y-titanium phosphate dihydrate Intercalation of n-alkylamines into misfit layer sulfides Layered structures of hydrated vanadium oxides Part -Single- crystal structure of Rb ,V205 and phase changes of rubidium intercalate Intercalation reactions of UTeO and USeO 1.New preparation method for surface-modified inorganic layered compounds Homogeneous precipitation from solution by urea hydrolysis a novel chemical route to the a-hydroxides of nickel and cobalt Synthesis and characterization of a novel layered titanium silicate JDF-L1 Structure of Zn(O,PC,H,CO,H) 5C6H,NH and XANES-EXAFS study of the intercalation of amines into Zn(0,PR) H,O zinc alkylphosphonates Intercalation of 2- 4-sulfanylpyridine 2,2- and 4,4'- dithiobispyndine into VOPO and gel-V,O interlayer spaces Synthesis of Al-intercalated montmorillonites using microwave irradiation Calorimetric study of intercalation of n-alkyldiamines into a-titanium hydrogenphosphate Interfacial failure Interfacial chemistry of adhesive joint failure an investigation by small area XPS imaging XPS and TOF-SIMS Intermetallic alloy A new method of nitrogenation of M2Fe17 powder alloy via chemical reaction with sodium azide (NaN,) as a nitrogen source (m=Y or Ln) Interstratification Dehydration-rehydration in magnesium vermiculite conversion from two-one and one-two water layer hydration states through the formation of interstratified phases Ion exchange Synthesis and ion-exchange properties of Na-4-mica Synthesis of three-dimensional compounds from alkali-metal ion- exchanged y-titanium phosphate Synthesis and structure determination of new layered perovskite compounds ALaTa207 and ACazTa3Olo (A =Rb Li) Ion-exchange resin Modified carbothermal reduction for the synthesis of ultrafine particle tungsten compounds dispersed in a microporous carbon matrix Ionic conductivity New oxide ion conducting solid electrolytes Bi4V2O11 M M =B Al Cr Y La LiSb(edta)(H,O) a convenient precursor to LiSbS and LiSbO From Bi4V2011 to Bi4V2Oi0 the Vv-V'v transformation in the Aurivillius-type framework Ionic conductivity of SrO-Ta,O and SrO-La,O3-Ta2O compounds Ionic interaction Self-assembly of non-linear optical chromophores through ionic interactions Ionicity Structure of two polymorphs of the TTF-TCNE charge-transfer complex and the degree of ionicity Iridium Structural and electronic properties of the compounds Ba,Ir,MO (M=Li Na Mg Y Lu Zr and Ce) Structural and magnetic properties of Sr4-xMxIr06 (M =Ca Zn Cd Li Na) Iron Iron-doped zlrconium silicate Part -The location of iron Iron-manganese hydroxycarbonate Iron-manganese hydroxycarbonate precursors in the synthesis of high-dispersity spinel mixed oxides Iron oxide-silica nanocomposite Magnetic iron oxide-silica nanocomposites Synthesis and charactenzation Iron-titanium oxide High-temperature electrical conductivity of FeTi03 and ilmenite Iron-yttrium acetylacetonate Study of the formation mechanism of complex oxides obtained by the sol-gel method influence of the structure of iron aluminium and yttnum acetylacetonate precursors on the phase composition of the ZrO ceramics Iron-zirconium oxide Study on the structure and reduction behaviour of the iron- zirconium oxide system Kanemite The reversible extraction of the hexamminecobalt(II1) cation by kanemite (NaHSi,O * 3H@) enhanced extraction in the presence of a cationic surfactant Kaolinite Chemically modified kaolinite Grafting of methoxy groups on the interlamellar aluminol surface of kaolinite K,O-MOO flux .Growth of emerald crystals by evaporation of a K,O-MOO flux Kramers-Kronig analysis Infrared reflection study of cofacially stacked phthalocyanines doped with iodine Langmuir-Blodgett film Examples of amphitropic polymers monolayer film Langmuir- Blodgett film and liquid-crystalline properties of some polymeric amphiphiles containing cholestanol moieties and those of some closely related non-polyrnenc amphiphiles structure of a centrosymmetric dye and the second-order non- linear optical properties of its non-centrosymmetric Langmuir- Blodgett films Z-type Langmuir-Blodgett film structures surface plasmon resonance second harmonic generation and fibre optic devices Controlling the structure of transparent Langmuir-Blodgett films for nonlinear optical applications Langmuir-Blodgett multilayers of six compact porphyrin amphiphiles Thin film formulations of substituted phthalocyanines Preparation of ultrafine particle multilayers using the Langmuir- Blodgett technique Preparation and characterisation of conductive Langmuir-Blodgett films of a tetrabutylammonium-Ni(dmit) complex 699.Preparation and characterization of Langmuir-Blodgett films of N-hexadecyl-8-hydroxy-2-quinolinecarboxamideand its lanthanum complex 'Molecular zips' evidence of the interdigitation of layers in Langmuir-Blodgett films of an optically non-linear dye and a compatible spacer Second-order non-linear optical properties of Langmuir-Blodgett films of a new azo compound (p-NO,)C6H,N=NCl,H,0(CH,),N(CH,),Cl,H,7Brand its europium complex Lanthanide Synthesis crystal structure and magnetic properties of Ln -,Sr,Ni04 solid solutions (Ln =La Nd Sm and Gd Lanthanum complex Preparation and charactenzation of Langmuir-Blodgett films of N-hexadecyl-8-hydroxy-2-quinolinecarboxamideand its lanthanum complex Lanthanum oxide I7O Solid-state NMR examination of La203 formation Laser-induced decomposition IR laser-induced decomposition of 2-chloroethenylsilane for chemical vapour deposition of Si/C phases Laser photolysis Laser-induced chemical vapour deposition of Si/C/H materials from monoorganylsilanes Laser photolytic studies of sensitizers for negative photoresists 2,7-diazidofluorene in poly(methy1 methacrylate) films Lattice simulation Space group symmetry and A1-0-P bond angles in A1Po4-5 xi1 Layered double hydroxide Incorporation of poly(acry1ic acid) poly (vinylsulfonate) and poly(styrenesu1fonate) within layered double hydroxides Rheology and microstructure of aqueous layered double hydroxide dispersions New preparation method for surface-modified inorganic layered compounds Thermal behaviour of Zn-Cr layered double hydroxides with hydrotalcite-like structures containing carbonate or decavanadate Hydrothermal conversion of amorphous NiFe -,Al,(OH) into crystalline phases Layered material Hydrothermal syntheses and crystal structures of new layered tungsten(v1) methylphosphonates M2(W0,),P03CH (M =NH Rb CS) A ,,Na NMR study of hydrous layered silicates Synthesis and structure determination of new layered perovskite compounds ALaTa,O and ACazTa,Olo (A =Rb Li) Precursor dependence of the nature and structure of non- stoichiometnc magnesium aluminium vanadates Synthesis and structure of Ba,InO,X (X=F C1 Br) and Ba,ScO,F oxide/halide ordenng in K,NiF,-type structures Thermal behaviour of Zn-Cr layered double hydroxides with hydrotalcite-like structures containing carbonate or decavanadate Homogeneous precipitation from solution by urea hydrolysis a novel chemical route to the a-hydroxides of nickel and cobalt Evidence of new layered cuprates in the Hg-A-Gd-Cu-0 system (A =Ba Sr) Stabilisation of Ba,CuO,Cl with the K2NiF structure by chemical substitution Structure and magnetotransport properties of the layered manganites RE ,MnZO7 (RE =La Pr Nd) Chemically modified kaolinite Grafting of methoxy groups on the interlamellar aluminol surface of kaolinite Mesostructured lamellar chromium oxide A neutron diffraction study of structural distortions in the Ruddlesden-Popper phase Na,La,Ti,O Synthesis and charactenzation of a novel layered titanium silicate JDF-L1 Structure of Zn(O3PC2H4CO2H) study of the intercalation of amines into Zn(0,PR) HzO zinc alkylphosphonates Layer structure .Reorganisation of layer structures formed from amphiphilic molecules Lead selenide Growth of lead selenide thin films by the successive ionic layer adsorption and reaction (SILAR) technique Lead sulfide Growth of strongly orientated lead sulfide thin films by successive ionic layer adsorption and reaction (SILAR) technique Li battery LiNi ,,Co,,O positive electrode materials relationships between the structure physical properties and electrochemical behaviour Light-emitting diode Improved electroluminescence performance of poly (3-alkylthiophenes) having a high head-to-tail (HT) ratio Liquid crystal Examples of amphitropic polymers monolayer film Langmuir- Blodgett film and liquid-crystalline properties of some polymeric amphiphiles containing cholestanol moieties and those of some closely related non-polymeric amphiphiles Synthesis and liquid crystal properties of phthalocyanine derivatives containing both alkyl and readily oxidised phenolic substituents Synthesis and properties of copper(I1) and oxovanadium(1v) complexes derived from polar Schiff’s bases Paramagnetic liquid-crystal side-chain polyacrylates containing Schiff-base copper(r1) complexes 533.Supermolecular alignment in a liquid crystal-polymer gel as studied optically and by dielectnc relaxation spectroscopy Thresholdless antiferroelectncity in liquid crystals and its application to displays Mesogenic properties of novel enamino ketone ligands and their copper(1r) complexes Structural vanation of liquid crystalline trioxadecalins Synthesis and mesogenic properties of 3,6-disubstituted cyclohex-2- en- 1-ones Stability of the antiferroelectnc phase in dimenc liquid crystals having two chiral centres with CF or CH groups evaluation of conformational and electric interactions Electroclinic and antiferroelectnc properties of (R)-(-)-nonan-3-yl 4- (4-dodecyloxybiphenyl-4-ylcarbonyloxy)-3-fluorobenzoate Highly twisting enantiomenc radial multiyne dopants for discotic liquid-crystalline systems Dielectnc relaxation in four cyclic liquid-crystalline oligosiloxanes with different ring size and spacer length Liquid-crystalline rod-coil polymers based on poly(ethy1ene oxide)s and the influence of the complexation of LiCF,SO on the liquid-crystalline assembly Molecular design of amphotropic materials influence of oligooxyethylene groups on the mesogenic properties of calamitic liquid crystals .Distinct ferroelectnc smectic liquid crystals consisting of banana shaped achiral molecules Phasmidic phases in macrocyclic liquid crystals The influence of heteroatoms and branchings on the liquid- crystalline properties of cyclotnveratrylene denvatives ortho-Palladated metallomesogens the effects of structural modifications on their liquid crystalline behaviour Synthesis and liquid-crystalline properties of novel laterally connected twins the influence of the connecting topology and the length of the rigid core Ferrocene-containing thermotropic liquid crystals laterally connected twins Linear precursors of liquid crystalline thermosets Liquid crystal polymers copolymers and elastomers containing a laterally attached mesogenic unit Influence of the host-guest interactions on the ferroelectric properties of mononuclear orthopalladated metallomesogen mixtures Synthesis and characterization of inorganic gels in a lyotropic liquid crystal medium Part 2-Synthesis of silica gels in lyotropic crystal phases obtained from cationic surfactants The synthesis and characterisation of a novel thiophene-based liquid crystal exhibiting ferro- fern- and antiferro-electric phase types Liquid metal infiltration Consumption of Sic whiskers by the Al-Sic reaction in aluminium- matrix Sic whisker composites Liquid-phase deposition Preparation and charactenzation of Au-dispersed T10 thin films by a liquid-phase deposition method Lithium antimony oxide The crystal structure of Li,SbO Lithium battery Preparation by a ‘chzmie douce’ route and characterization of LiNi,Mn -zO (0 <z <1) cathode matenals Lithium extraction Structural change of the LiMn,O spinel structure induced by extraction of lithium Lithium insertion Low-temperature mixed spinel oxides as lithium insertion compounds MVO (M =Nb Ta) mixed oxides sol-gel synthesis structural and thermal charactenzation and electrochemical Li’ insertion Lithium intercalation Lithium intercalation and copper extraction in spinel sulfides of general formula CuzMSn3S (M =Mn Fe Co Ni) Low-temperature synthesis and electrochemical lithium intercalation behaviour of defect Li-Mn-0 spinel oxide Lithium-nickel-manganese oxide Preparation by a ‘chimie douce’ route and characterization of LiNi,Mn -,02(0 dz d 1)cathode materials Lithium polymer-electrolyte cell Sol-gel-derived vanadium and titanium oxides as cathode matenals in high-temperature lithium polymer-electrolyte cells Local density approximation Stability of silicon carbide structures from clusters to solid surfaces Low-frequency microechography Characterization of heterogeneous structure in a polymer object manufactured by stereolithography with low-frequency microechography xi11 Low-tempera ture sta bilisa tion Low-temperature stabilisation of tetragonal zirconia by antimony Luminescence Influence of crystal structure on the luminescence properties of bismuth(Im) europium(m) and dysprosium(m) in Y,SiOs Magic-angle spinning nuclear magnetic resonance I7O Solid-state NMR examination of La203 formation Magnesiosilicate framework Sodalite-type NasMg3Si,0,,(OH) and Na,Mg,Si,O,,(OH,Cl) novel framework magnesiosilicates Magnesium aluminium vanadate Precursor dependence of the nature and structure of non- stoichiometnc magnesium aluminium vanadates Magnesium-calcium hydroxyapatite Preparation and charactenzation of magnesium~alcium hydroxyapa ti tes Magnesium oxide Synthesis and characterization of vanous MgO and related systems Magnetic properties.Synthesis crystal structure and magnetic properties of Ln,-,Sr,NiO solid solutions (Ln=La Nd Sm and Gd LiNi -,,C0,O2 positive electrode matenals relationships between the structure physical properties and electrochemical behaviour Structural and magnetic properties of Sr4-xMxIr06 (M =Ca Zn Cd Li Na) Manganese oxide-zirconium oxide solid solutions An X-ray diffraction Raman spectroscopy thermogravimetry and magnetic study Synthesis crystal structure and spectroscopic properties of the NH,NiPO nH,O (n= 1,6) compounds magnetic behaviour of the monohydrated phase Magnetic electrical and lslEu Mossbauer properties of EuPtGe Preparation of ultrafine particle multilayers using the Langmuir- Blodgett technique Magnetic properties of ternary chromium sulfides V,Cr -3 (Obxbl0) Generation of magnetic metal particles in zeolite by borohydnde reduction at ambient temperature Crystal structures and magnetic properties of La,Zn,Mg -,Ir06 .Investigations on the charge transport in LaMnO at low temperatures Two-dimensional molecular-based fernmagnets incorporating decamethylmetallocenium cations Evidence of new layered cuprates in the Hg-A-Gd-Cu-0 system (A = Ba Sr) Crystal structure and magnetic properties of Balo(MnFeF,l~,Cl,),FxC12~,(x=O 85) Structural relationships with the apatite-type structure Transition-metal stannides with high tin content Os4Sn17 RhSn RhSn and IrSn Magnetic iron oxide-silica nanocomposites Synthesis and characterization Magnetic structure The electronic and magnetic structures of stoichiometnc SrCoO ASW calculations Magnetic susceptibility Spin-crossover behaviour of the coordination polymer Fe"(CSHSN),Ni1'(CN) Crystal structure and physical properties of UAuSi and UAu Synthesis reactivity structure and electronic properties of "(CH,),] c60-1 5thf fullendes with simple hexagonal packing Magnetotransport properties Structure and magnetotransport properties of the layered manganites RE ,Sr1 ,Mn207 (RE = La Pr Nd) Manganese Single-crystal X-ray structure analysis of Mn-substituted banum hexaaluminates as-grown and after reduction Manganese oxide Manganese oxide-zirconium oxide solid solutions An X-ray diffraction Raman spectroscopy thermogravimetry and magnetic study Low-temperature synthesis and electrochemical lithium intercalation behaviour of defect Li-Mn-0 spinel oxide MAS NMR Additive-assisted pressureless sintenng of carbothermal p'-sialon an X-ray and solid-state MAS NMR study Synthesis and structure of Ba21n0,X (X=F C1 Br) and Ba,ScO,F oxide/halide ordenng in K,NiF,-type structures Volatile products formed by carboreduction and nitndation of clay mixtures with silica and elemental silicon linked polysiloxanes prepared from polymethylhydrosiloxane The structures of strontium tellunte and strontium tellunde aluminate sodalites studied by powder neutron diffraction EXAFS IR and MAS NMR spectroscopies I7ONMR investigation of hafnia and ternary oxides Mass spectrometry Pyrolysis study of methyl-substituted Si- H containing gels as precursors for oxycarbide glasses by combined thermogravimetry gas chromatographic and mass spectrometnc analysis Synthesis and charactenzation of vanous MgO and related systems Mechanical alloying Formation mechanism of a crystalline Ag,,Pd solid solution by impact ball-matenals interaction Influence of size and shape of metallic silver and palladium powders on the Ag,,Pd solid solution formation by mechanical alloying Membrane Fabrication of La -,Sr,CoO -,thin layers on porous supports by a polymeric sol-gel process Merlinoi te Synthesis and crystal structure of zeolite W resembling the mineral merlinoite Mesogen Mesogenic properties of novel enamino ketone ligands and their copper@) complexes Electroclinic and antiferroelectric properties of (R)-(-)-nonan-3-yl 4- (4'-dodecyloxybiphenyl-4-ylcarbonyloxy)-3-fluorobenzoate,Liquid crystal polymers copolymers and elastomers containing a laterally attached mesogenic unit Mesomorphism Ferroelectric and antiferroelectnc liquid crystalline phases in some pyridine carboxylic aad denvatives Mesoporous material Preparation and charactensation of mesoporous high-surface-area zirconium(1v) oxide Synthesis and charactenzation of inorganic gels in a lyotropic liquid crystal medium Part -Synthesis of silica gels in lyotropic crystal phases obtained from cationic surfactants Metal-insulator transition Metal-insulator transition and molecular dynamics in (NH,)K,C,,,.Metallic conductivity Metamagnetism in EuPdIn and EuAuIn Magnetic electncal and lslEu Mossbauer properties of EuPtGe Structure refinement magnetic susceptibility electncal conductivity and europium-151 Mossbauer spectroscopy of EuNiIn A new metallic ordered perovskite thin film La ,Srl ,Cu,O pulsed laser deposition and microstructural charactenzation Transition-metal stannides with high tin content Os,Sn17 RhSn RhSn and IrSn Metallomesogen Ferrocene-containing thermotropic liquid crystals laterally connected twins Influence of the host-guest interactions on the ferroelectnc properties of mononuclear orthopalladated metallomesogen mixtures Metalloporphyrin derivative Photo-active and electro-active protein films prepared by reconstitution with metalloporphynns self-assembled on gold .Metal phosphonate Synthesis and crystal structures of two metal phosphonates M(H0,PC6H,) (M = Ba Pb) xiv Metamagnetism Metamagnetism in EuPdIn and EuAuIn Methane oxidation Surface and bulk properties catalytic activities and selectivities in methane oxidation on near-stoichiometnc calcium hydroxyapatites Methox ysilane Coordination environment of copper(I1) dunng the sol-gel process of an aminated alkoxide Methyl acrylate Liquid crystal polymers copolymers and elastomers containing a laterally attached mesogenic unit Methyl cellulose Preparation of photochromic spiropyrans linked to methyl cellulose and photoregulation of their properties Solution of an organic crystal structure from X-ray powder diffraction data by a generalized rigid-body Monte Carlo method crystal structure determination of l-methylfluorene The molecular dipole moment of the non-linear optical 3-methyl empirical studies Mica Ordering and manipulation of MoS platelets on differently charged micas by atomic force microscopy Microcluster Molecular dynamics study of T10 microclusters Microporous material On the crystallisation and nature of the microporous boron- aluminium 0x0 chlonde BAC( lo) Solvothermal synthesis and structural characterisation of the first ammonium cobalt gallium phosphate hydrate NH CCoGa,P,O,,(H,O),I Synthesis and charactenzation of a novel microporous aluminophosphate AlP0,-JDF (2AlP04* HOCH,CH,NH,) from alcohol systems Space group symmetry and A1-0-P bond angles in A1P04-5 Microwave heating Microwave-assisted selective deoxygenation of layer- and chain- containing oxides Microwave irradiation Synthesis of Al-intercalated montmorillonites using microwave irradiation Mineral acid Electrorheological properties of polypyrrole prepared by the action of mineral acids on pyrrole Misfit layer sulfide Intercalation of n-alkylamines into misfit layer sulfides Mixed hydroxycarbonate Structural study by energy dispersive X-ray diffraction of amorphous mixed hydroxycarbonates containing Co Cu Zn Al Mixed metal polymer Preparation voltammetry coulometry and electrochemical quartz crystal gravimetry of [Os(bipy),( PVPS),ClRu(edta)] redox polymers Mixed oxide Low-temperature mixed spinel oxides as lithium insertion compounds Synthesis and catalytic properties of perovskite-related phases in the La-Sr-Co-Cu-Ru-0 system Structural and magnetic properties of Sr4-*Mx1rO6 (M =Ca Zn Cd Li Na) Investigation of the formation of Ru0,-based mixed oxide coatings by secondary ion mass spectrometry Iron-manganese hydroxycarbonate precursors in the synthesis of high-dispersity spinel mixed oxides Structural chemistry of SrMn .Fe,O xz03 Stoichiometry structures and polymorphism of spinel-like phases L1l 33xzn2 2xT11 +O 671~47 Mixed oxides Si02-Zr02 and SiO,-TiO by a non-hydrolytic sol-gel route MOCVD LuBa,Cu,O thin films prepared using MOCVD Synthesis and spectroscopic charactensation of MOO thin films Thermal decomposition of V(NEt,) in an MOCVD reactor a low- temperature route to vanadium carbonitride coatings 1501.Carbonyl sulfide (OCS) as a sulfur-containing precursor in MOCVD a study of mixtures of Me,Cd and OCS in the gas and solid phases and their use in MOCVD Molecular dipole moment The molecular dipole moment of the non-linear optical 3-methyl 4- nitropyridine N-oxide molecule X-ray diffraction and semi- empincal studies Molecular dynamics Metal-insulator transition and molecular dynamics in (NH,)K,C Molecular dynamics simulation Molecular dynamics study of Ti0 microclusters Molecular modelling Molecular modelling of the physical and mechanical properties of two polycyanurate network polymers Molecular motion Molecular motions near the glass transition in diethylene glycol bis(ally1 carbonate) as studied by dielectnc relaxation spectroscopy Molecular sieve Synthesis and precise characterization of large single crystals of as- synthesized CrAPO-5 Hz [Cr osAl 62P12048]F1,-1 6TEA Nucleation and crystal growth of analcime from clear .aluminosilicate solutions Molecular zip 'Molecular zips' evidence of the interdigitation of layers in Langmuir-Blodgett films of an optically non-linear dye and a compatible spacer Molten salt Precipitation of finely divided Al,O powders by a molten salt method Molybdenum oxide Synthesis and spectroscopic characterisation of MOO thin films Monoalk ylsilane Laser-induced chemical vapour deposition of Si/C/H materials from monoorganylsilanes Monolithic polymer Chemical modification of monolithic poly(styrene4ivinylbenzene) PolyHIPE@ materials Monomethylamine New preparation of superconducting alkali-metal fullerides utilizing monomethylamine as solvent Monte Carlo calculation Soluhon of an orgamc crystal structure from X-ray powder diffraction data by a generaked ngd-body Monte Carlo method crystal structure detemnation of l-methylfluorene Montmorillonite Synthesis of Al-intercalated montmonllonites using microwave irradiation Morphology control Morphology control of thin LiCoO films fabncated using the electrostatic spray deposition (ESD) technique MoS platelets Ordering and manipulation of MoS platelets on differently charged micas by atomic force microscopy Mossbauer effect Structural relaxation and crystallization of semiconducting vanadate glass accompanying a jump of the electncal conductivity Mossbauer spectroscopy Lithium intercalation and copper extraction in spinel sulfides of general formula Cu,MSn3Ss (M =Mn Fe Co Ni) Spin-crossover behaviour of the coordination polymer Fe"(C5H5N),Ni1'(CN) Organometallic cation-exchanged phyllosilicates vanable- temperature 57Fe Mossbauer spectroscopic and related studies of the adsorption of dimethylaminomethylferroceneon clays and pillared clays Structural chemistry of SrMn -,Fe,O x x03 Motor oil Synthesis of long chain alkyl and chloroalkyl esters of perfluorosalicylic acid new potential high temperature antifnction additives for advanced motor oils A ',Na NMR study of hydrous layered silicates Nanocomposite Incorporation of poly(acry1ic acid) poly(vinylsulfonate) and poly(styrenesu1fonate) within layered double hydroxides xv Nanoparticles Synthesis of CdS and CdSe nanoparticles by thermolysis of diethyldithio- or diethyldiseleno-carbamates of cadmium Effect of pyridine upon gas-phase reactions between H,S and Me,Cd control of nanoparticle growth Nanostructured ceramic FTIR analysis of the surface of nanostructured aluminium nitnde powder prepared via chemical synthesis Negative photoresist Laser photolytic studies of sensitizers for negative photoresists 2,7- diazidofluorene in poly(methy1 methacrylate) films Neodymium cuprate Electrodeposition of thin-film rare-earth-metal oxocuprates Network structure Crystal structure and magnetic properties of Ba,o(MnFeF,,-,C1,),F,C1,- (x=O 85) Structural relationships with the apatite-type structure Neutron diffraction Study of the order-disorder transition in yttna-stabilised zirconia by neutron diffraction Synthesis and structure of Ba,InO,X (X =F C1 Br) and Ba,ScO,F oxide/halide ordering in K,NiF,-type structures A neutron diffraction study of structural distortions in the Ruddlesden-Popper phase NazLazTi3010 Neutron powder diffraction The structure of the calcined aluminophosphate ALP04-5.determined by high-resolution X-ray and neutron powder diffraction Nickel-dithiolene complex Syntheses characterization and non-linear optical properties of nickel complexes of multi-sulfur 1,2-dithiolene with strong near-IR absorption Nickel ferrite aluminate Hydrothermal conversion of amorphous NiFe2 -,Al,(OH) into crystalline phases Niobium oxide .Studies on the electrochemical deposition of niobium oxide Nitrene Laser photolytic studies of sensitizers for negative photoresists 2,7- diazidofluorene in poly(methy1 methacrylate) films Ni trodisplacement Nitrodisplacement reactions and the synthesis of bis(ether anhydride)s from dihydroxynaphthalenes Nitrogen-15 NMR spectroscopy Oxygen-nitrogen ordenng in yttnum nitrogen melilite Nitrogenation A new method of nitrogenation of M,Fe17 powder alloy via chemical reaction with sodium azide (NaN,) as a nitrogen source (m=Y or Ln) Nitrogen dioxide Nitrogen dioxide and volatile sulfide sensing properties of copper zinc and nickel chromite Non-hydrolytic condensation Mixed oxides SiO2-ZrO2 and Si02-Ti02 by a non-hydrolytic sol-gel route Non-linear optics Structure and non-linear optical properties of phosphine oxide denvatives structure of a centrosymmetnc dye and the second-order non- linear optical properties of its non-centrosymmetric Langmuir- Blodgett films Synthesis polymorphic charactenzation and structural comparisons of the non-linear optically active and inactive forms of polymorphs of 3-(nitroanilino)cycloalk-2-en-l-ones,Controlling the structure of transparent Langmuir-Blodgett films for nonlinear optical applications Self-assembly of non-linear optical chromophores through ionic interactions Boron derivatives containing a bithiophene bndge as new materials for non-linear optics Novel optically transparent polyesters containing a high density of second-order non-linear optically active chromophores ‘Molecular ups’ evidence of the interdigitation of layers in Langmuir-Blodgett films of an optically non-linear dye and a compatible spacer Simple acid-base hydrolytic chemistry approach to new materials for second-order non-linear optics Strong optical second-harmonic generation in a chiral diaminodicyanoquinodimethane system The molecular dipole moment of the non-linear optical 3-methyl 4- nitropyridine N-oxide molecule X-ray diffraction and semi- empirical studies Two-step refractive index changes by photoisomerization and photobleaching processes in the films of non-linear optical polyurethanes and a urethane-urea copolymer Second-order non-linear optical properties of Langmuir-Blodgett films of a new azo compound (p-NO,)C6H4N=NC,oH60(CH,)3N(CH3)2C18H37Brand its europium complex Syntheses characterization and non-linear optical properties of nickel complexes of multi-sulfur 1,2-dithiolene with strong near-IR absorption Preparation and characterisation of high refractive index Pb0-Ti0,-Te02 glass systems Non-stoichiometry Correlating thermochemical data of the oxygen non-stoichiometric compound YBa,Cu,O,- with the oxygen content Nucleation Monodisperse iron-based particles precipitation in liquid polyols Nucleation and crystal growth of analcime from clear aluminosilicate solutions Odd-even effect Thermal and optical properties of chiral twin liquid crystalline bis(cholestery1) alkanedioates Oligo(furan-2,s-diylvinylene) Ohgo(furan-2,5-diylvinylene)sas n-conjugating spacers in linearly extended hybrid tetrathiafulvalene analogues Oligothiophene Electrochemical doping of a-ethyl-disubstituted oligothiophenes and electrical conductivities of the resulting radical-cation salts .Optical constant Infrared reflection study of cofacially stacked phthalocyanines doped with iodine Optical properties Processing and optical properties of spin-coated polystyrene films containing CdS nanoparticles Optical waveguide fabrication Optical waveguide fabncation using a polyrnenc azine containing the 3-dodecylthiophene moiety Optochemical sensor Optochemical HCl gas detection based on tetraphenylporphine dispersed in ethylcellulose Order-disorder transition Study of the order-disorder transition in yttria-stabilised zirconia by neutron diffraction Organic-inorganic composite Novel composite organic-inorganic semiconductor sensors for the quantitative detection of target organic vapours Organic-inorganic hybrid material Hybrid organic-inorganic matenals a land of multidisciplinanty .Organic-inorganic nanocomposite New preparation method for surface-modified inorganic layered compounds Organic polyester Novel optically transparent polyesters containing a high density of second-order non-linear optically active chromophores Organic vapour detection Novel composite organic-inorganic semiconductor sensors for the quantitative detection of target organic vapours Organomineral Chemically modified kaolinite Grafting of methoxy groups on the interlamellar aluminol surface of kaolinite Ortho-palladated metallomesogen ortho-Palladated metallomesogens the effects of structural modifications on their liquid crystalline behaviour Oxide New oxide ion conducting solid electrolytes Bi,V,O M M =B Al Cr Y La Oxide halide Synthesis and structure of Ba,InO,X (X=F C1 Br) and BazSc03F oxide/halide ordering in K,NiF,-type structures Oxide insulator The solid solution BaLi,-,Cu,PO (x<O 5) an example of Cut single-ion luminescence in oxide insulators Oxide ion conductivity Preparation and electrical conductivity of neodymium-europium oxide fluorides xv1 Charactensation and properties of the non-stoichiometnc perovskite Ca,Fe -,Nb,O (045 <x <0 65) Oxide one-pot synthesis Processable aluminosilicate alkoxide precursors from metal oxides and hydroxides. The oxide one-pot synthesis process Oxotitanium(1v) phthalocyanine Chemical behaviour of oxotitanium(rv) phthalocyanine (OTiPc) solutions associated with the preparation of OTiPc monolayers and multilayers Oxovanadium phosphate Intercalation of 2- 4-sulfanylpyndine 2,2'-and 4,4 -dithiobispyridine into VOPO and gel-V,O interlayer spaces Oxycarbide glass Pyrolysis study of methyl-substituted Si-H containing gels as precursors for oxycarbide glasses by combined thermogravimetry gas chromatographic and mass spectrometnc analysis Ox ycarbonate Sheanng mechanism in the Bi-Sr-Cu oxycarbonates HREM study of a new collapsed phase ~i,,~r29~u,,(~~,)7~ P-Oxygen effect The influence of heteroatoms and branchings on the liquid- crystalline properties of cyclotriveratrylene derivatives Oxygen content Correlating thermochemical data of the oxygen non-stoichiometric compound YBa,Cu,O,- with the oxygen content Oxygen-17 solid-state nuclear magnetic resonance Palladium catalysed cross-coupling Synthesis and liquid-crystalline properties of novel laterally connected twins the influence of the connecting topology and the length of the rigid core Paramagnetism Paramagnetic liquid-crystal side-chain polyacrylates containing Schiff-base copper(I1) complexes Pentagonal-prism tunnel structure Preparation of BaTi40 by a sol-gel method and its photocatalytic activity for water decomposition .Perfluorosalicylic acid ester Synthesis of long chain alkyl and chloroalkyl esters of perfluorosalicylic acid new potential high temperature antifriction additives for advanced motor oils Perovskite Preparation and electrical properties of KCa -,La,Nb3010 Synthesis and catalytic properties of perovskite-related phases in the La-Sr-Co-Cu-Ru-0 system Synthesis and structure determination of new layered perovskite compounds ALaTa207 and ACa2Ta301 (A= Rb Li) A new metallic ordered perovskite thin film La 4Sr1 ,CU~O pulsed laser deposition and microstructural charactenzation Structural chemistry of SrMnl-,Fe,O,- xz0 Charactensation and properties of the non-stoichiometric perovskite Ca,FE,-,Nb,O,O(O 45<x<O 65) Perovskite structure Structural and electronic properties of the compounds Ba,Ir,MO (M =Li Na Mg Y Lu Zr and Ce) Preparation characterization and surface structure of coprecipitated high-area Sr,TiOz+,(O<x< 1) powders Crystal structures and magnetic properties of La,Zn,Mg -,IrO Investigations on the charge transport in LaMnO at low temperatures Perovskite-type oxide Fabncation of La,-,Sr,CoO,- thin layers on porous supports by a polymeric sol-gel process Preparation and characterlzation of perovskite-type Ln',Ln" -,COO for electroceramic applications Phase diagram The YBa,Cu,O phase diagram Phase formation Effect of oxygen partial pressure on the T1,Ba,CuO,T1,Ba,CaCu2O transformation Phase transformation Diffusion of transition metals (Co,Ni) and its effects on sol-gel derived ZrO polymorphic stabilities 435.Phase transition Synthesis and liquid-crystalline properties of novel laterally connected twins the influence of the connecting topology and the length of the ngid core Phasmidic liquid crystal Phasmidic phases in macrocyclic liquid crystals Phenylphthalamic acid Copper ion binding to N-phenylphthalamic acid studied by 13C nuclear magnetic resonance and electron paramagnetic resonance model interaction of polyamic acid with copper Phorphine Optochemical HC1 gas detection based on tetraphenylporphine dispersed in ethylcellulose Phosphine oxide Structure and non-linear optical properties of phosphine oxide denvatives Photoacoustic spectroscopy Synthesis and characterization of 11-VI semiconductor nanoparticulates by the reaction of a metal alkyl polymer adduct with hydrogen sulfide Photoactivity Photo-active and electro-active protein films prepared by reconstitution with metalloporphynns self-assembled on gold Photocatalysis Preparation of BaTi,09 by a sol-gel method and its photocatalytic activity for water decomposition Photochemistry Two-step refractive index changes by photoisomerization and photobleaching processes in the films of non-linear optical polyurethanes and a urethane-urea copolymer Photochromism Preparation of photochromic spiropyrans linked to methyl cellulose and photoregulation of their properties Photoconductivity XPS and XRD study of photoconductive CdS films obtained by a chemical bath deposition process Photoelectron spectroscopy XPS and XRD study of photoconductive CdS films obtained by a chemical bath deposition process Photoemission spectroscopy EELS and photoemission study of antimony-doped Cd,Sn04 ceramics Photographic emulsion Structure of rhodanine cyanine dyes spectroscopy and performance in photographic emulsions Photographic film Synthesis and physical performance of indole and benzimidazole cyanine dyes Photoluminescence Photoluminescence study of (CaO) ,(ZnO) powder solids in air Improved electroluminescence performance of poly (3-alkylthiophenes) having a high head-to-tail (HT) ratio Photopolymer charactenzation of heterogeneous structure in a polymer object manufactured by stereolithography with low-frequency microechography Photoregulation Preparation of photochromic spiropyrans linked to methyl cellulose and photoregulation of their properties Phthaloc yanine Chemical behaviour of oxotitanium(1v) phthalocyanine (OTiPc) solutions associated with the preparation of OTiPc monolayers and multilayers Self-assembled monolayers of phthalocyanine denvatives on glass and silicon Synthesis and liquid crystal properties of phthalocyanine derivatives containing both alkyl and readily oxidised phenolic substituents .Thin film formulations of substituted phthalocyanines Synthesis and characterization of novel bridged phthalocyaninatoruthenium complexes Infrared reflection study of cofaclally stacked phthalocyanines doped with iodine Theoretical determination of the molecular and solid-state electronic structures of phthalocyanine and largely extended phthalocyanine macrocycles XVll Ph yllosilica te Organometallic cation-exchanged phyllosilicates variable- temperature 57Fe Mossbauer spectroscopic and related studies of the adsorption of dimethylaminomethylferrocene on clays and pillared clays Pillared material Intercalation ability of hydrolysed aluminium species in n-alkylmonoamine a-zirconium phosphate compounds New porous Ga/Cr mixed oxide pillared a-zirconium phosphate matenals Protonation and olation of 2,2’-bipyndyl and 1,lO-phenanthroline in y-titanium phosphate dihydrate Enhanced fluorescence of coumarin laser dye in the restricted geometry of a porous nanocomposite Platelet assembly Ordering and manipulation of MoS platelets on differently charged micas by atomic force microscopy Podand Molecular design of amphotropic materials influence of oligooxyethylene groups on the mesogenic properties of calamitic liquid crystals Polarisation microscopy Thermotropic phase transitions in 5,15-bis(4- alkoxyphenyl)octaalkylporphyrins Polar Schiff bases Synthesis and properties of copper(r1) and oxovanadium(1v) complexes denved from polar Schiff’s bases Poly (3-alkylthiophene).Improved electroluminescence performance of poly (3-alkylthiophenes) having a high head-to-tail (HT) ratio Pol yacr ylate Paramagnetic liquid-crystal side-chain polyacrylates containing Schiff-base copper(I1) complexes Polyamic acid Copper ion binding to N-phenylphthalamic acid studied by I3C nuclear magnetic resonance and electron paramagnetic resonance model interaction of polyamic acid with copper,Conference Diary Pol yamide Rigid-rod aramids incorporating polymethylated monomers Polyaramid Rigid-rod aramids incorporating polymethylated monomers Polyarylene ether sulfone(s) Molecular modelling of the physical and mechanical properties of two polycyanurate network polymers Poly (ar ylenevin ylene) The synthesis of an electronically asymmetnc substituted poly (arylenevinylene) poly { 2-(2’-ethylhexyloxy)-5-[(E)-4’-nitrostyry1)- 1,4-phenylenevinylene} Pol ycation Adsorption of polycations on clays an in sztu study using 13,Cs solution-phase NMR Polycyanurate Molecular modelling of the physical and mechanical properties of two polycyanurate network polymers Polyester Synthesis of polyesters containing 9,10-diacetoxyanthracene-2,6-diyl moieties via a precursor polymer approach Poly(ether imide) Nitrodisplacement reactions and the synthesis of bis(ether anhydride)s from dihydroxynaphthalenes Synthesis and properties of poly (ether imide)s derived from dihydroxynaphthalenes Poly(ethy1ene oxide) Conductivities of some PEO complexes of lithium and sodium salts with aromatic and heterocyclic anions Liquid-crystalline rod-coil polymers based on poly(ethy1ene oxide)s and the influence of the complexation of LiCF,SO on the liquid-crystalline assembly Poly (ethyliminoalane) Preparation of AlN from poly(ethy1iminoalane) uia pyrolysis Poly (E-caprolactone) Preparation and properties of epoxidized natural rubber/poly(s- caprolactone) self-vulcanizable blends Po1yHIPE Chemical modification of monolithic poly(styrene-divinylbenzene) PolyHIPE@ materials Pol yimide Evaluation of bis( perfluorophenyl azide)s as cross-linkers for a soluble polyimide Polymer Ultrasound in matenals chemistry Polymer electrolyte Poly [oxymethylene-oligo(oxyethy1ene)lnetwork electrolytes Polymeric azine Optical waveguide fabncation using a polymeric azine containing the 3-dodecylthiophene moiety Polymer intercalation Incorporation of poly(acry1ic acid) poly (vinylsulfonate) and poly(styrenesu1fonate) within layered double hydroxides Polymer matrix Laser photolytic studies of sensitizers for negative photoresists 2,7- diazidofluorene in poly(methy1 methacrylate) films .Polymer-nanoparticle composite Synthesis and charactenzation of 11-VI semiconductor nanoparticulates by the reaction of a metal alkyl polymer adduct with hydrogen sulfide Polymer network Poly [oxymethylene-oligo(oxyethylene)]network electrolytes Polymer synthesis Synthesis of polyesters containing 9,10-diacetoxyanthracene-2,6-diyl moieties via a precursor polymer approach Pol ymeth ylhydrosiloxane linked polysiloxanes prepared from polymethylhydrosiloxane Polymorphism Synthesis polymorphic charactenzation and structural compansons of the non-linear optically active and inactive forms of polymorphs of 3-(nitroanilino)cycloalk-2-en-l-ones,123 Polyol process Preparation of colloidal silver dispersions by the polyol process Part 1-Synthesis and characterization Monodisperse iron-based particles precipitation in liquid polyols Influence of size and shape of metallic silver and palladium powders on the Ag,,Pd solid solution formation by mechanical alloying Poly [oxymethylene-oligo (ox yeth ylene)] Poly [oxymethylene-oligo(oxyethylene)] network electrolytes Poly (phen yleneethynylene) Synthesis and magnetic behaviour of polyradical poly( 1,3- phenyleneethynylene) with n-toporegulated pendant stable aminoxyl and imine N-oxide-aminoxyl radicals Polyp yrrole Electrorheological properties of polypyrrole prepared by the action of mineral acids on pyrrole Synthesis and charactenzation of organic conductors derived from (1H-pyrrol-3-y1)acetic acid esters Polyradical Synthesis and magnetic behaviour of polyradical poly( 1,3- phenyleneethynylene) with n-toporegulated pendant stable aminoxyl and imine N-oxide-aminoxyl radicals Pol ysiloxane linked polysiloxanes prepared from polymethylhydrosiloxane Poly (st yrendivin ylbenzene).Chemical modification of monolithic poly (styrene-divinylbenzene) PolyHIPE@ matenals Poly (sulfur nitride) Electrochemical syntheses of two doped forms of poly(su1fur nitride) {[SN],[AsF,]} and ([SN],,[AsF,]} Poly [tetra (pyrrol-1-yl)silane] Synthesis and gas sensing properties of poly [tetra( pyrrol-1- yl)silane] Polyurethane film Two-step refractive index changes by photoisomenzation and photobleaching processes in the films of non-linear optical polyurethanes and a urethane-urea copolymer Poly (vinylidene fluoride) Structure and properties of sulfonated poly [(vinylidene fluoride)-g-styrene] porous membranes Polyvin ylp yrrolidone Preparation of colloidal silver dispersions by the polyol process Part -Synthesis and charactenzation XVlll Porous film Unit-cell symmetnes and Raman spectra of calcium- and Structure and properties of sulfonated poly [(vinylidene fluoride)-neodymium-doped banum cerate proton-conducting ceramic g-styrene] porous membranes electrolytes Porous mixed oxide Companson of X-ray patterns and Raman spectra of n=2 and New porous Ga/Cr mixed oxlde pillared a-zirconium phosphate Aunvillius phases by pnncipal component analysis matenals Rare-earth-metal oxide fluoride Porphyrin Preparation and electncal conductiwty of neodymium-europium Langmuir-Blodgett multilayers of six compact porphynn oxide fluondes amphiphiles Redox active Positive charge electrophotography Synthesis and liquid crystal properties of phthalocyanine derivatives N-(2,4,7-Tnnitrofluorenylidene)anilines-new electron transport containing both alkyl and readily oxidised phenolic matenals in positive charge electrophotography substituents Positive electrode material Redox polymer LiNi -,,Co,,O positive electrode matenals relationships between Preparation voltammetry coulometry and electrochemical quartz the structure physical properties and electrochemical crystal gravimetry of [Os( bipy),(PVPS),ClRu(edta)] redox behaviour polymers Potential model Refractive index Space group symmetry and Al-0-P bond angles in A1Po4-5 Preparation and charactensation of high refractive index Pb0-Ti02-Te02 glass systems 1Powder RehydrationA new solution route to silicates Part 4-submicronic nrcon Dehydration-rehydration in magnesium vermiculite conversion powders from two-one and one-two water layer hydration states Powder diffraction through the formation of interstratified phases Electrochemical synthesis and thermal decomposition of nrconia Reversible extraction gels containing vanous metal ions.The reversible extraction of the hexamminecobalt(m) cation by Powder neutron diffraction kanemite (NaHSi20 -3H20) enhanced extraction in the Powder neutron diffraction study of LiMnVO presence of a cationic surfactant Powder X-ray diffraction Thermotropic phase transitions in 5,15-bis(4- Rhodanine cyanine dye alkoxyphenyl)octaalkylporphynns,357 Structure of rhodanine cyanine dyes spectroscopy and performance A combined time-of-flight powder neutron and powder X-ray in photographic emulsions Rietveld analysis diffraction study of ternary chromium sulfides V,Cr -3 Powder neutron diffraction study of LiMnVO (Odxdl 0) Precursor Rietveld refinement Preparation of AlN from poly(ethyhminoa1ane) via pyrolysis Structural change of the LiMn,O spinel structure induced by Principal component analysis extraction of lithium Comparison of X-ray patterns and Raman spectra of n=2 and Synthesis and structure of Ba21n03X (X =F Cl Br) and Ba,ScO,F Aurivillius phases by principal component analysis oxide/halide ordenng in KzNiF,-type structures Protein film.The crystal structure of Li,SbO Photo-active and electro-active protein films prepared by Robinson-type annulation reconstitution with metalloporphynns self-assembled on gold Synthesis and mesogenic properties of 3,6-disubstituted cyclohex-2- Protonic conductor Rocksalt-perovskite intergrowth phase . Unit-cell symmetnes and Raman spectra of calcium- and Synthesis and crystal structures of 'Lil 8K0 9M 75Zr2 2506neodymium-doped banum cerate proton-conducting ceramic Cu Mg) a family of novel rocksalt-perovskite intergrowth electrolytes phases Pulsed laser deposition Rocksalt structure A new metallic ordered perovskite thin film La 4Sr1 6C~8022.The crystal structure of Li,SbO pulsed laser deposition and microstructural characterization Rod-coil polymer Push-pull quinonoid and the influence of the complexation of LiCF,SO on the Strong optical second-harmonic generation in a chiral liquid-crystalline assembly diaminodicyanoquinodimethane system Rubidium vanadium oxide Solvate-switchable powder second harmonic generation in a Layered structures of hydrated vanadium oxides Part -Single-push-pull quinonoid system crystal structure of Rb 5V,05 and phase changes of rubidium Pyrolysis intercalate Pyrolysis study of methyl-substituted Si-H containing gels as Ruddlesden-Popper phase precursors for oxycarbide glasses by combined thermogravimetry gas chromatographic and mass A neutron diffraction study of structural distortions in the Ruddlesden-Popper phase Na,La,Ti30 1823spectrometnc analysis RutheniumPreparation of AlN from poly(ethy1iminoalane) via pyrolysis Synthesis and charactenzation of novel bndged "Si MAS NMR investigation of the pyrolysis process of cross-phthalocyaninatoruthenium complexes linked polysiloxanes prepared from polymethylhydrosiloxane Ruthenium dioxide Radiochemical technique Investigation of the formation of Ru0,-based mixed oxide coatings Chemical models for the cure of epoxy resins the influence of by secondary ion mass spectrometry hydrogen bonding Rutile.Radiolysis Molecular dynamics study of TiO microclusters Optical and EPR spectroscopic studies of silver clusters in Ag,Na-Y Selectivity and compositional dependence of response of gas- zeolite by y-irradiation sensitive resistors Part -Properties of some rutile solid Thin film deposition of Ge,C,,H by radiolysis of GeH,-C,H solution compounds mixtures Scaffolding mechanism Raman scattering Preparation and characterisation of mesoporous high-surface-area Synthesis and structural investigation of the Eu -,Bi,VO scheelite zirconium(1v) oxide phase X-ray diffraction Raman scattering and Eu3 + Scanning electron microscopy luminescence Preparation of uniform zinc oxide colloids by controlled double-jet Raman spectroscopy precipitation Manganese oxide-zirconium oxide solid solutions An X-ray Schiff base diffraction Raman spectroscopy thermogravimetry and Paramagnetic liquid-crystal side-chain polyacrylates containing magnetic study Schiff-base copper@) complexes XlX Secondary ion mass spectrometry Investigation of the formation of Ru0,-based mixed oxlde coatings by secondary ion mass spectrometry Second harmonic generation structure of a centrosymmetric dye and the second-order non- linear optical properties of its non-centrosymmetric Langmuir- Blodgett films Synthesis polymorphic characterization and structural comparisons of the non-linear optically active and inactive forms of polymorphs of 3-(nitroanilino)cycloalk-2-en-l-ones,Z-type Langmuir-Blodgett film structures surface plasmon resonance second harmonic generation and fibre optic devices Controlling the structure of transparent Langmuir-Blodgett films for nonlinear optical applications ‘Molecular zips’ evidence of the interdigitation of layers in Langmuir-Blodgett films of an optically non-linear dye and a compatible spacer Strong optical second-harmonic generation in a chiral diaminodicyanoquinodimethane system Second-order non-linear optical properties of Langmuir-Blodgett films of a new azo compound (p-NO,) C,H4N=NC,oH,0(CH2),N(CH,)2Cl,H,7Brand its europium complex Solvate-switchable powder second harmonic generation in a push-pull quinonoid system Seebeck coefficient The YBa,Cu,O phase diagram Selective reflection Thermal and optical properties of chiral twin liquid crystalline bis(cholestery1) alkanedioates Selectivity Protonation and olation of 2,2’-bipyndyl and 1,lO-phenanthroline in y-titanium phosphate dihydrate Self-assembled monolayer Self-assembled monolayers of phthalocyanine derivatives on glass and silicon Self-assembly Self-assembly of non-linear optical chromophores through ionic interactions Simple acid-base hydrolytic chemistry approach to new materials for second-order non-linear optics Self-propagating high-temperature synthesis Solid-state NMR charactenzation of P-sialons from self-propagating high-temperature synthesis Self-vulcanizable polymer blend Preparation and properties of epoxidized natural rubber/poly(e- caprolactone) self-vulcanizable blends Semiconducting oxide Gas-sensitive resistors surface interaction of chlorine with semiconducting oxides Semiconducting vanadate glass Structural relaxation and crystallization of semiconducting vanadate glass accompanying a jump of the electrical conductivity Semiconductivity Preparation and electrical properties of KCa,-xLaxNb,Ol Electrodeposition of thin-film rare-earth-metal oxocuprates Novel composite organic-inorganic semiconductor sensors for the quantitative detection of target organic vapours Oriented cadmium oxide thin solid films Synthesis properties and performances of electrodeposited bismuth tellunde films Synthesis and charactenzation of novel bridged phthalocyaninatoruthenium complexes .High- temperature electncal conductivity of FeTiO and ilmenite Selectivity and composition dependence of response of gas-sensitive resistors Investigations on the charge transport in LaMnO at low temperatures Processing and optical properties of spin-coated polystyrene films containing CdS nanoparticles A density-functional based tight-binding approach to III-V semiconductor clusters Synthesis and characterization of II-VI semiconductor nanoparticulates by the reaction of a metal alkyl polymer adduct with hydrogen sulfide Sensor Novel composite organic-inorganic semiconductor sensors for the quantitative detection of target organic vapours Shearing mechanism Sheanng mechanism in the Bi-Sr-Cu oxycarbonates HREM study of a new collapsed phase B~,,S~,,CU,,(CO,),O,~ Shift correlation spectra A 23Na NMR study of hydrous layered silicates Shock synthesis Synthesis and characterization of a shock-synthesized cubic B-C-N solid solution of composition BC2 ,N f!-Si a Ion.Additive-assisted pressureless sintering of carbothermal p’-sialon an X-ray and solid-state MAS NMR study Volatile products formed by carboreduction and nitridation of clay mixtures with silica and elemental silicon Solid-state NMR characterization of p-sialons from self-propagating high-temperature synthesis r-Sialon Carbothermal reduction of sillimanite SILAR technique Growth of strongly orientated lead sulfide thin films by successive ionic layer adsorption and reaction (SILAR) technique Growth of lead selenide thin films by the successive ionic layer adsorption and reaction (SILAR) technique Zinc sulfide thin films grown by SILAR on poly(viny1 chloride) and polycarbonate substrates Silica Preparation of ceria-coated composite silica particles Chemomechanical polishing of silica and silicon by fluoride- and oxide-based reagents identification of a reaction intermediate Volatile products formed by carboreduction and nitridation of clay mixtures with silica and elemental silicon Mixed oxides SiO,-ZrO and Si0,-TiO by a non-hydrolytic sol-gel route Silica gel Synthesis and characterization of inorganic gels in a lyotropic liquid crystal medium Part 2-Synthesis of silica gels in lyotropic crystal phases obtained from cationic surfactants Silica-titania Role of titanium in T10 SiO sol-gels an X-ray diffraction study Silicon Chemomechanical polishing of silica and silicon by fluonde- and oxide-based reagents identification of a reaction intermediate Silicon carbide Consumption of Sic whiskers by the Al-Sic reaction in aluminium- matrix Sic whisker composites Structure of carbon produced by hydrothermal treatment of p-Sic powder Stability of silicon carbide structures from clusters to solid surfaces Silicon nitride Composition and microstructure of nanosized amorphous and crystalline silicon nitride powders before during and after densification Sillimanite Carbothermal reduction of sillimanite Silver cluster Optical and EPR spectroscopic studies of silver clusters in Ag,Na-Y zeolite by y-irradiation Silver-palladium solid solution Formation mechanism of a crystalline Ag,,PdSo solid solution by impact ball-matenals interaction Influence of size and shape of metallic silver and palladium powders on the Ag70Pd30 solid solution formation by mechanical alloying Single-crystal X-ray diffraction Solvothermal synthesis and structural characterisation of the first ammonium cobalt gallium phosphate hydrate NH4CCoGa2P,O,,(H,0)21 Single-ion luminescence The solid solution BaLi,-,Cu,PO (x605) an example of Cu+ single-ion luminescence in oxide insulators Sintering Additive-assisted pressureless sintenng of carbothermal p’-sialon an X-ray and solid-state MAS NMR study xx Sodalite The structures of strontium tellurite and strontium telluride aluminate sodalites studied by powder neutron diffraction EXAFS IR and MAS NMR spectroscopies Sodalite-type Na,Mg3Sig024(0H) and Na,Mg3Sig0,,(OH,Cl) novel framework magnesiosilicates Sodium azide A new method of nitrogenation of M,Fel powder alloy via chemical reaction with sodium azide (NaN,) as a nitrogen source (m =Y or Ln) Sodium fluorophlogopite mica .Synthesis and ion-exchange properties of Na4-mica Soft chemistry synthesis Preparation by a 'chirnze douce' route and charactenzation of LiNi,Mn -zO (0 <z <1) cathode matenals Sol-gel Sol-gel-derived vanadium and titanium oxides as cathode matenals in high-temperature lithium polymer-electrolyte cells Study of the formation mechanism of complex oxides obtained by the sol-gel method influence of the structure of iron aluminium and yttnum acetylacetonate precursors on the phase composition of the ZrO ceramics Role of titanium in T10 SiO sol-gels an X-ray diffraction study Diffusion of transition metals (Co,Ni) and its effects on sol-gel derived ZrO polymorphic stabilities Electrical switching in VO sol-gel films Coordination environment of copper(I1) during the sol-gel process of an aminated alkoxide Fabrication of La -xSrxCo03-6 thin layers on porous supports by a polyrnenc sol-gel process MVO (M =Nb Ta) mixed oxides sol-gel synthesis structural and thermal charactenzation and electrochemical Li+ insertion A new solution route to silicates Part 4-submicronic zircon powders Mixed oxides Si0,-Zr02 and S10,-T102 by a non-hydrolytic sol-gel route Preparation of BaTi,09 by a sol-gel method and its photocatalytic activity for water decomposition 1921.Preparation of anatase brookite and rutile at low temperature by non-hydrolytic sol-gel methods Solid base catalyst Synthesis and characterization of various MgO and related systems Solid electrolyte New oxide ion conducting solid electrolytes Bi,V,O M M =B Al Cr Y La Preparation and electrical conductivity of neodymium-europium oxide fluondes Ionic conductivity of SrO-Ta,O and SrO-La,03-Ta,0 compounds Solid solution Synthesis crystal structure and magnetic properties of Ln -xSrxNi04 solid solutions (Ln =La Nd Sm and Gd The solid solution BaLi -,Cu,PO (x <O 5) an example of Cu' single-ion luminescence in oxide insulators Manganese oxide-zirconium oxlde solid solutions An X-ray diffraction Raman spectroscopy thermogravimetry and magnetic study Ionic conductivity of Sr0-Taz05 and Sr0-La203-Taz05 compounds Selectivity and composition dependence of response of gas-sensitive resistors Crystal structures and magnetic properties of La,Zn,Mg -xIr06 Stoichiometry structures and polymorphism of spinel-hke phases L1l 33xzn2 2xTil +O 67x04 Synthesis and charactenzation of a shock-synthesized cubic B-C-N solid solution of composition BC ,N Solid-state electrochemistry Structural change of the LiMn,O spinel structure induced by extraction of lithium Solid-state NMR spectroscopy Thermal reactions of alkali-leached aluminosilicates studied by XRD and solid-state "Al ,'Si and 23Na MAS NMR Solid-state NMR charactenzation of p-sialons from self-propagating high-temperature synthesis Solid-state reaction Preparation and electncal conductivity of neodymium-europium oxide fluondes EELS and photoemission study of antimony-doped Cd,Sn04 ceramics Sodalite-type Na,Mg3Sig0,,(OH) and Na,Mg3Si90,,(0H,C1) novel framework magnesiosilicates Soluble polyimide Evaluation of bis( perfluorophenyl azide)s as cross-linkers for a soluble polyimide .Solution-phase NMR Adsorption of polycations on clays an in situ study using 13,Cs solution-phase NMR Solvothermal synthesis Solvothermal synthesis and structural charactensation of the first ammonium cobalt gallium phosphate hydrate NH4CCoGa2P3012(H20)21,Sonochemistry Ultrasound in matenals chemistry Spin-coated polystyrene film Processing and optical properties of spin-coated polystyrene films containing CdS nanoparticles Spin crossover behaviour Spin-crossover behaviour of the coordination polymer Fell(C,H,N),Ni"(CN) Spinel Structural change of the LiMn,O spinel structure induced by extraction of lithium Low-temperature mixed spinel oxides as lithium insertion compounds Lithium intercalation and copper extraction in spinel sulfides of general formula Cu,MSn3S8 (M =Mn Fe Co Ni) Nitrogen dioxide and volatile sulfide sensing properties of copper zinc and nickel chromite Iron-manganese hydroxycarbonate precursors in the synthesis of high-dispersity spinel mixed oxides Powder neutron diffraction study of LiMnVO Stoichiometry structures and polymorphism of spinel-like phases L1l 33xZn2-txT1l+O 67.~~4,Low-temperature synthesis and electrochemical lithium intercalation behaviour of defect Li-Mn-0 spinel oxide Hydrothermal conversion of amorphous NiFe -,Al,(OH) in to crystalline phases Spiropyran Preparation of photochromic spiropyrans linked to methyl cellulose and photoregulation of their properties Spontaneous polarization Influence of the host-guest interactions on the ferroelectnc properties of mononuclear orthopalladated metallomesogen mixtures Squaraine structure of a centrosymmetric dye and the second-order non- linear optical properties of its non-centrosymmetric Langmuir- Blodgett films Stereolithography Charactenzation of heterogeneous structure in a polymer object manufactured by stereolithography with low-frequency microechography Strontium tantalate Ionic conductivity of SrO-Ta,O and SrO-La,0,-Taz05 compounds Strontium titanium oxide Preparation characterization and surface structure of coprecipitated high-area Sr,TiO,+,(O< x <1) powders Structural distortion A neutron diffraction study of structural distortions in the Ruddlesden-Popper phase NazLazTi3010 Structural relaxation and crystallization.Structural relaxation and crystallization of semiconducting vanadate glass accompanying a jump of the electrical conductivity Successive ionic layer adsorption and reaction Growth of strongly orientated lead sulfide thin films by successive ionic layer adsorption and reaction (SILAR) technique Growth of lead selenide thin films by the successive ionic layer adsorption and reaction (SILAR) technique Zinc sulfide thin films grown by SILAR on poly(viny1 chloride) and polycarbonate substrates Sulfan ylp yridine Intercalation of 2- 4-sulfanylpyridine 2,2‘- and 4,4- dithiobispyridine into VOP04 and gel-V20 interlayer spaces Sulfide Nitrogen dioxide and volatile sulfide sensing properties of copper zinc and nickel chromite Superconducting oxide Correlating thermochemical data of the oxygen non-stoichiometric .compound YBa,Cu,O,- with the oxygen content Superconductivity New preparation of superconducting alkali-metal fullerides utilizing monomethylamine as solvent Microstructure of superconducting copper oxycarbonate thin films of the Ba-Ca-Cu-C-0 system Thermoanalytical study of oxoanion-substituted cuprate superconductors Surface analysis FTIR analysis of the surface of nanostructured aluminium nitride powder prepared via chemical synthesis Surface modification New preparation method for surface-modified inorganic layered compounds Chemically modified kaolinite Grafting of methoxy groups on the interlamellar aluminol surface of kaolinite Surface plasmon resonance Z-type Langmuir-Blodgett film structures surface plasmon resonance second harmonic generation and fibre optic devices Surface structure Preparation characterization and surface structure of coprecipitated high-area Sr,TiO +,( < x < 1) powders Surfactant Preparation of uniform zinc oxide colloids by controlled double-jet precipitation Tantalum silicide Chemical vapour deposition of tantalum silicide thin films from difluorosilylene and tantalum halides Telechelic polymer Preparation and properties of epoxidized natural rubber/poly(E- caprolactone) self-vulcanizable blends Telluride The structures of strontium tellurite and strontium tellunde aluminate sodalites studied by powder neutron diffraction EXAFS IR and MAS NMR spectroscopies Tellurite The structures of strontium tellurite and strontium telluride aluminate sodalites studied by powder neutron diffraction EXAFS IR and MAS NMR spectroscopies Temperature-programmed desorption Synthesis and characterization of various MgO and related systems Temperature-programmed reduction Study on the structure and reduction behaviour of the iron- zirconium oxide system Characterization of RuMo-SiO catalysts A comparative study before and after CO hydrogenation reaction Tensile properties Synthesis and properties of poly(ether imide)s denved from dihydroxynaphthalenes Ternary hafnium oxide ”0 NMR investigation of hafnia and ternary hafnium oxides Ternary sulfide Magnetic properties of ternary chromium sulfides V,Cr -,S4 (O<x<lO) TerphenyI Synthesis and liquid-crystalline properties of novel laterally connected twins the influence of the connecting topology and the length of the rigid core Tetrachloromethane Surface and bulk properties catalytic activities and selectivities in methane oxidation on near-stoichiometnc calcium hydroxyapatites Tetrac yanoplatinate Electrochemical quartz crystal microbalance studies of partially oxidized tetracyanoplatinum salts Tetragonal zirconia Low-temperature stabilisation of tetragonal zirconia by antimony Tetra thiafulvalene Oligo(furan-2,5-diylvinylene)sas n-conjugating spacers in linearly extended hybnd tetrathiafulvalene analogues Tetromethox ychalcogenanthrene Structure dielectnc relaxation and electrical conductivity of 2,3,7,8- tetramethoxy-chalcogenanthrene-2,3-dichloro-5,6-dicyano-benzoquinone charge-transfer complexes Thermal behaviour Preparation and characterization of perovskite-type Ln’xLn”l -,COO for electroceramic applications .Thermal behaviour of Zn-Cr layered double hydroxides with hydrotalcite-like structures containing carbonate or decavanadate Synthesis and properties of poly(ether imide)s derived from dihydroxynaphthalenes Thermoanalytical study of oxoanion-substituted cuprate superconductors Electrochemical synthesis and thermal decomposition of zirconia gels containing various metal ions Thermochemical data Correlating thermochemical data of the oxygen non-stoichiometric compound YBa,Cu,O,- with the oxygen content Thermodynamics.Correlating thermochemical data of the oxygen non-stoichiometric compound YBa,Cu,O -,with the oxygen content Thermoeiectrical material Synthesis properties and performances of electrodeposited bismuth telluride films Thermogravimetry Manganese oxide-zirconium oxide solid solutions An X-ray diffraction Raman spectroscopy thermogravimetry and magnetic study Pyrolysis study of methyl-substituted Si- H containing gels as precursors for oxycarbide glasses by combined thermogravimetry gas chl amatographic and mass spectrometric analysis Thermol ysis Synthesis of CdS and CdSe nanoparticles by thermolysis of diethyldithio- or diethyldiseleno-carbamates of cadmium Thiadiazole Molecular design of amphotropic matenals influence of oligooxyethylene groups on the mesogenic properties of calamitic liquid crystals Thin film Growth of gallium oxide thin films from gallium acetylacetonate by atomic layer epitaxy Chemical behaviour of oxotitanium(1v) phthalocyanine (OTiPc) solutions associated with the preparation of OTiPc monolayers and multilayers Self-assembled monolayers of phthalocyanine derivatives on glass and silicon Laser-induced chemical vapour deposition of Si/C/H matenals from monoorganylsilanes Growth of strongly orientated lead sulfide thin films by successive ionic layer adsorption and reaction (SILAR) technique Microstructure of superconducting copper oxycarbonate thin films of the Ba-Ca-Cu-C-0 system Studies on the electrochemical deposition of niobium oxide XPS and XRD study of photoconductive CdS films obtained by a chemical bath deposition process Electrical switching in VO sol-gel films Investigation of the formation of Ru0,-based mixed oxide coatings by secondary ion mass spectrometry LuBa,Cu,O -,thin films prepared using MOCVD Thin film formulations of substituted phthalocyanines Oriented cadmium oxide thin solid films Morphology control of thin LiCoO films fabricated using the electrostatic spray deposition (ESD) technique Oxidation of alkaline-earth-metal sulfide powders and thin films Growth of lead selenide thin films by the successive ionic layer adsorption and reaction (SILAR) technique Simple acid-base hydrolytic chemistry approach to new matenals for second-order non-linear optics Chemical vapour deposition of tantalum silicide thin films from difluorosilylene and tantalum halides Speciation and the nature of ZnO thin films from chemical bath deposition A new metallic ordered perovskite thin film La ,CU~O pulsed laser deposition and microstructural charactenzation XXll Amorphous and crystalline copper sulfides CuS .Synthesis and spectroscopic charactensation of MOO thin films Zinc sulfide thin films grown by SILAR on poly(viny1 chloride) and polycarbonate substrates Thin film deposition of Ge,C,,H by radiolysis of GeH,-C,H mixtures A water-resistant precursor in a wet process for TiO thin film formation Thin layer Fabncation of L~,-,S~,COO,-~ thin layers on porous supports by a polymeric sol-gel process Thiophene The synthesis and charactensation of a novel thiophene-based liquid crystal exhibiting ferro- fern- and antiferro-electric phase types Thresholdless antiferroelectricity Thresholdless antiferroelectncity in liquid crystals and its application to displays Time-of-flight powder neutron diffraction A combined time-of-flight powder neutron and powder X-ray diffraction study of ternary chromium sulfides V,Cr -3 (O<x< lo) Time resolved microwave conductivity Thermotropic phase transitions in 5,15-bis(4- alkoxyphenyl)octaalkylporphynns,357 Titania Preparation of cena-coated composite silica particles Mixed oxides SiO,-ZrO and S10,-TiO by a non-hydrolytic sol-gel route Preparation of anatase brookite and rutile at low temperature by non-hydrolytic sol-gel methods Titanium Role of titanium in T10 SiO sol-gels an X-ray diffraction study Titanium dioxide Molecular dynamics study of Ti0 microclusters Titanium-edta complex A water-resistant precursor in a wet process for TiO thin film formation Titanium hydrogenphosphate Calorimetric study of intercalation of n-alkyldiamines into cr-titanium hydrogenphosphate Titanium oxide Sol-gel-derived vanadium and titanium oxides as cathode materials in high-temperature lithium polymer-electrolyte cells Preparation and charactenzation of Au-dispersed T10 thin films by a liquid-phase deposition method y-Titanium phosphate Synthesis of three-dimensional compounds from alkali-metal ion-exchanged y-titanium phosphate 415.Protonation and olation of 2,2'-bipyridyl and 1,lO-phenanthroline in y-titanium phosphate dihydrate TlBaCaCuO Effect of oxygen partial pressure on the T1,Ba2CuO,T1,Ba2CaCu,OX transformation TOF-SIMS Interfacial chemistry of adhesive joint failure an investigation by small area XPS imaging XPS and TOF-SIMS Transition-metal diffusion Diffusion of transition metals (Co,Ni) and its effects on sol-gel derived ZrO polymorphic stabilities Transition-metal oxides Microwave-assisted selective deoxygenation of layer- and chain- containing oxides Transition-metal stannide Transition-metal stannides with high tin content Os,Sn RhSn RhSn and IrSn Transmission electron microscopy Synthesis and charactenzation of 11-VI semiconductor nanoparticulates by the reaction of a metal alkyl polymer adduct with hydrogen sulfide Trioxadecalin Structural variation of liquid crystalline tnoxadecalins TTF-TCNE Structure of two polymorphs of the TTF-TCNE charge-transfer complex and the degree of ionicity Tungsten compound Modified carbothermal reduction for the synthesis of ultrafine particle tungsten compounds dispersed in a microporous carbon matrix XXlll Tungsten oxide Hydrothermal syntheses and crystal structures of new layered tungsten(v1) methylphosphonates M,( WO,),PO3CH3 (M =NH4 Rb CS) Gas-sensitive resistors surface interaction of chlonne with semiconducting omdes Twin mesogens Synthesis and liquid-crystalline properties of novel laterally connected twins the influence of the connecting topology and the length of the ngid core Ultrafine particles Preparation of ultrafine particle multilayers using the Langmuir- Blodgett technique Modified carbothermal reduction for the synthesis of ultrafine particle tungsten compounds dispersed in a microporous carbon matnx Ultrasound Ultrasound in materials chemistry Uranium gold silicide Crystal structure and physical properties of UAuSi and UAu Uranium tellurium oxide Intercalation reactions of UTeO and USeO Urea Homogeneous precipitation from solution by urea hydrolysis a novel chemical route to the a-hydroxides of nickel and cobalt Structure and dynamics of hydrogen bonding guests in urea inclusion compounds .Urethane-urea copolymer Two-step refractive index changes by photoisomenzation and photobleaching processes in the films of non-linear optical polyurethanes and a urethane-urea copolymer Valence effective Hamiltonian Theoretical determination of the molecular and solid-state electronic structures of phthalocyanine and largely extended phthalocyanine macrocycles Vanadium carbonitride Thermal decomposition of V(NEt,) in an MOCVD reactor a low- temperature route to vanadium carbonitride coatings Vanadium chromium sulfide A combined time-of-flight powder neutron and powder X-ray diffraction study of ternary chromium sulfides V,Cr -3 (O<x<lO) Vanadium dioxide Electrical switching in VO sol-gel films Vanadium mixed oxide MVO (M =Nb Ta) mixed oxides sol-gel synthesis structural and thermal characterization and electrochemical Li+ insertion Vanadium oxide Sol-gel-denved vanadium and titanium oxides as cathode materials in high-temperature lithium polymer-electrolyte cells Computer modelling of V205 surface structures crystal morphology and ethene sorption Layered structures of hydrated vanadium oxides Part -Single- crystal structure of Rb ,V,05 and phase changes of rubidium intercalate Vanadium pentoxide Intercalation of 2- 4-sulfanylpyndine 2,2'- and 4,4- dithiobispyridine into VOPO and gel-V,O interlayer spaces Vapour-grown carbon fibre A model of duplex structure for short vapour-grown carbon fibres Vermiculite Dehydration-rehydration in magnesium vermiculite conversion from two-one and one-two water layer hydration states through the formation of interstratified phases Water decomposition Preparation of BaTi40 by a sol-gel method and its photocatalytic activity for water decomposition Water splitting A carbon-bearing nickel(I1) fernte a tailor-made solid reactant for two-step thermochemical water splitting at 300" C Xerogel Sol-gel-denved vanadium and titanium oxides as cathode materials in high-temperature lithium polymer-electrolyte cells X-Ray diffraction Role of titanium in Ti0 SiO sol-gels an X-ray diffraction study.Manganese oxide-zirconium oxide solid solutions An X-ray diffraction Raman spectroscopy thermogravimetry and magnetic study N-(2,4,7-Tnnitrofluorenylidene)anilines-new electron transport matenals in positive charge electrophotography Dehydration-rehydration in magnesium vermiculite conversion from two-one and one-two water layer hydration states through the formation of interstratified phases X-Ray photoelectron spectroscopy Interfacial chemistry of adhesive joint failure an investigation by small area XPS imaging XPS and TOF-SIMS Preparation and electncal conductivity of neodymium-europium oxide fluorides Composition and microstructure of nanosized amorphous and crystalline silicon nitnde powders before during and after densification X-Ray structure Synthesis and structural investigation of the Eu -,Bi,V04 scheelite phase X-ray diffraction Raman scattenng and Eu3+ luminescence YBaCuO The YBa,Cu,O phase diagram YNiA14 structure Structure refinement magnetic susceptibility electrical conductivity and europium-1 Mossbauer spectroscopy of EuNiIn Yttria-stabilised zirconia Study of the order-disorder transition in yttria-stabilised zirconia by neutron diffraction Yttrium nitrogen melilite Oxygen-nitrogen ordenng in yttnum nitrogen melilite Yttrium ox yorthosilica te Influence of crystal structure on the luminescence properties of bismuth(m) europium(Ir1) and dysprosium(II1) in Y,SiO Zeolite Synthesis and crystal structure of zeolite W resembling the mineral merlinoite Optical and EPR spectroscopic studies of silver clusters in Ag,Na-Y zeolite by y-irradiation Generation of magnetic metal particles in zeolite by borohydnde reduction at ambient temperature .Nucleation and crystal growth of analcime from clear aluminosilicate solutions Zinc Photoluminescence study of (CaO) -,(ZnO) powder solids in air Zinc oxide Preparation of uniform zinc oxide colloids by controlled double-jet precipitation Speciation and the nature of ZnO thin films from chemical bath deposition Zinc sulfide Zinc sulfide thin films grown by SILAR on poly(viny1 chloride) and polycarbonate substrates Synthesis and charactenzation of 11-VI semiconductor nanoparticulates by the reaction of a metal alkyl polymer adduct with hydrogen sulfide Zircon A new solution route to silicates Part -submicronic zircon powders Zirconia Surface reactivity and bulk properties of ZrO Part -Thermochemistry of ZrO Y,O,-ZrO and K-ZrO aerogels in and H Surface reactivity and bulk properties of ZrO Part -Importance of homogeneity in the stabilisation of high surface area Ce0,-ZrO aerogels Mixed oxides SiO,-ZrO and Si0,-TiO by a non-hydrolytic sol-gel route Low-temperature stabilisation of tetragonal zirconia by antimony Zirconia gel Electrochemical synthesis and thermal decomposition of zirconia gels containing vanous metal ions Zirconium oxide Preparation and characterisation of mesoporous high-surface-area zirconium(rv) oxide Study of the formation mechanism of complex oxides obtained by the sol-gel method influence of the structure of iron aluminium and yttnum acetylacetonate precursors on the phase composition of the ZrO ceramics Manganese oxide-zirconium oxide solid solutions An X-ray diffraction Raman spectroscopy thermogravimetry and magnetic study Diffusion of transition metals (Co,Ni) and its effects on sol-gel derived ZrO polymorphic stabilities Zirconium phosphate Intercalation ability of hydrolysed aluminium species in n-alkylmonoamine a-zirconium phosphate compounds New porous Ga/Cr mixed oxide pillared a-zirconium phosphate matenals Zirconium silicate Iron-doped zirconium silicate Part -The location of iron XXlV Conference Diary December British Liquid Crystal Society -One Day Symposium -Challenges Ahead in Surfactant Liquid Crystals Wirral UK Dr I Howell or Dr P B Warren Unilever Research Port Sunlight Laboratory Quarry Road East Bebington Wirral Merseyside L63 3JW UK.E-mail patrick.warren@unilever.com;Tel +151 3407/3812; Fax +151 December 19-21 Inorganic Mechanisms Discussion Group -UK Symposium University of York UK Professor M B Davies Applied Sciences Anglia Polytechnic University East Road Cambridge CB1 1PT E-mail mdavies@bridge.anglia.ac.uk;Tel +44 (0)1223 363271; Fax +44 (0)1223 February 9-13 Minerals Metals and Materials Orlando FL USA. TMS Meeting Services Dept Commonwealth Dr Warrendale PA USA March 3-8 Liquid Crystals Zakopane Poland Mr J Zielinsk WAT Inst of Applied Physics Kaliskiegostr. PL-01489 Warszawa Poland E-mail zielj@wat.waw.pl; Fax +48 March 22-27 ISCOM'97 International Symposium on Crystalline Organic Metals Superconductors and Ferromagnets Sesimbra Portugal Professor Manuel Almeida Departamento de Quimica Instituto Tecnologico e Nuclear P-2686 Sacavem Codex Portugal.E-mail malmeida@itnl.itn.pt; Tel +351 19550021; Fax +351 March 24-26 British Liquid Crystal Society Annual Conference Southampton UK Professor T J Sluckin Faculty of Mathematical Studies University of Southampton Southampton SO17 lBJ UK E-mail tjs@maths.soton.ac.uk; Tel +44 3680; secretary 5150; Fax 5147; WWW http://www.soton.ac.uk/blcs97/ April 7-11 MRS Spring Meeting San Francisco CA USA Materials Research Society Meetings Dept McKnight Rd Suite Pittsburgh PA 15237-6006 USA Fax +1 April International Symposium on Applications of Magnetic Resonance in Materials Science Guildford UK Professor G A Webb or Dr J N Hay.The Department of Chemistry University of Surrey Guildford GU2 5XH UK Tel +1483 800; Fax +1483 . April 13-17 Spring ACS National Meeting San Francisco California USA American Chemical Society Meetings PO Box 20th St Station Washington DC 20036-8598 USA April 13-17 Eighth Biennial Workshop on Organometallic Vapor Phase Epitaxy California USA TMS Customer Service Commonwealth Drive Warrendale PA USA E-mail csc@tms.org; Tel Ext 270; Fax April 21-25 International Conference on Metallurgical Coatings and. Thin Films California USA Robert V Hillery G E Aircraft Engines One Neumann Way Mail Drop H85 Cincinnati OH 45215-6301 USA April 22-25 12th International Conference on Solid Compounds of Transition Elements Saint-Malo France H Noel E-mail scte97@univ-rennesl.fr; Tel +33 55; Fax +33 04; WWW http://www.univ- rennes1.fr/scte97 May 4-9 Gordon Research Conference on "Biodegradable Polymers" Barga Italy Emo Chiellini Department of Chemistry & Industrial Chemistry University of Pisa via Risorgimento Pisa Italy. E-mail chlmeo@dcci.unipi.it; Tel +39 918299; Fax +39 28438; WWW http://www.grc.uri.edu May 25-28 International Conference on New Biomedical Materials (Applied and Basic Studies) Ancona Italy Dr Parvez Haris Department of Biological Sciences School of Applied Sciences De Montfort University Hawthorn Building. The Gateway Leicester LE1 9BH UK E-mail pharis@dmu.ac.uk; Fax +44 or May 25-28 Chemistry Energy and the Environment Estoril Portugal CCsar Sequeira Instituto Superior Tecnico Lisboa Cedex Portugal Phone/Fax May 25-29 ISIC 9,9th International Symposium on Intercalation Compounds Bordeaux France ISIC Centre de Recherche Paul-PascaYCNRS Avenue A Schweitzer F-33600 Pessac France May 25-30 IEEE 5th International Conference on Properties & Applications of Dielectric Materials Seoul Korea Professor Joon-Ung Lee Department of Electrical Engineering Kwangwoon University 447-1 Wolgye-Dong Nowon-ku Seoul 139-701 Korea Tel +82 5144; Fax +82 XXV May 26-28 EPDIC -5; 5th European Powder Diffraction Conference Parma Italy Professor G Artioli Dipartimento di Scienze della Terra Universita' di Milano Via Botticelli23 1-20133 Milano Italy E-mail artioli@iummix terra unimi it Tel +39 Fax +39 June 3-6 5th International Symposium on Metallomesogens Neuchiitel Switzerland Professor R Deschenaux Universite de Neuchiitel Institut de Chimie Av de Bellevaux Neuchiitel Switzerland E-mail congres ism97@ich unine ch July 6-11 13th International Meeting NMR Spectroscopy University of Exeter UK Contact Dr J F Gibson. The Royal Society of Chemistry Burlington House London W1V OBN UK E-mail conferences@rsc org Fax +44 (0)171 July 21-25. The 3rd International Conference on Materials Chemistry University of Exeter UK Contact Dr J F Gibson. The Royal Society of Chemistry Burlington House London W1V OBN UK E-mail conferences@rsc org Fax +44 (0)171 WWW http llwww ex ac uk/chemweblmc3/ August 17-22 36th IUPAC Congress Geneva Switzerland Conference Secretariat IUPAC'97 c/o AKM Congress Service PO Box CH-1218 Le Grand-SaconnedGE Switzerland Tel +41 Fax +41 August 24-27 ZMPC '97 International Symposium on Zeolites and Microporous Crystals Tokyo Japan Dr Takahashi Tatsumi Secretary ZMPC '97 Engineering Research Institute Faculty of Engineering. The University of Tokyo Yayoi Tokyo Japan August 24-28 Seventeenth European Crystallographic Meeting ECM Lisboa Portugal ECWSecretariat Dept Engenharia Quimica Instituto Superior Ticnico Av Rovisco Pais Lisboa Portugal E-mail romao@itqb unl pt Tel +351 (1)442 Ext Fax +351 (1)442 August 1-Third European Congress on Catalysis September Krakow Poland Congress Secretariat EuropaCat-3 Institute of Catalysis and Surface Chemistry Polish Academy of Sciences ul Niezapominajek PL-30239 Krakow Poland E-mail ncczerwe@cyf-kr edu pl Tel +48 Fax +48 September 1-5 RSC Autumn Meeting University of Aberdeen Scotland. Contact Dr J F Gibson. The Royal Society of Chemistry Burlington House London W1V OBN UK E-mail conferences@rsc org Fax +44 (0)171 September 2-5 Dalton Discussion No Bioinorganic Chemistry Norwich UK Dr A K Powell School of Chemical Sciences UEA Norwich NR4 7TJ E-mail A PowellOuea ac uk September 7-11 Autumn ACS National Meeting Las Vegas Nevada USA American Chemical Society Meetings PO Box 20th St Station Washington DC 20036-8598 USA September 8-1 ECSSC-97 VIth European Conference on Solid State Chemistry Zurich Switzerland ECSSC-97 Mrs E Fahrnbuhl Laboratory of Inorganic Chemistry ETH Zurich Universitatstr CH-8092 Zurich Switzerland WWW http llwww inorg chem ethz ch/ecssc/ecssc hmtl September 14-19 International Conference on f Elements Paris France J-C Krupa Institut de Physique Nucleaire F-91406 Orsay-Cedex France E-mail krupa@frcpnll in2p3 fr Tel Fax September 21-26 Actinides '97 Conference Baden-Baden Germany Professor J Fuger E-mail act97@itu fzk de Tel Fax September 23-26 Second World Congress on Emulsion Bordeaux France CME Place Rene Clair Boulogne-Billancourt France Tel Fax October 4-9 Fifth Mediterranean School on Science and Technology of Advanced Polymer Based Materials Naples Italy MEDNET Fifth Mediterranean School Dr G Ragosta Istituto di Ricerca e Tecnologia delle Materie Plastiche Via Toiano 6-80072 Arc0 Felice (Napoli) Italy E-mail rago@niail irtemp na cnr it Tel (169-2521 Fax October 12-17 Composites at Lake Louise '97 Lake Louise Canada Dr Patrick S Nicholson Chairman Composites at Lake Louise Department of Materials Science & Engmeering McMaster University Main St West Hamilton Ontario L8S 4L7 Canada Qenotes a new or amended entry this month Entries in the Conference Diary are published free of charge If you wish to include an announcement please send full details to Journal of Materials Chemzstry Editorial Office. 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ISSN:0959-9428    

DOI:10.1039/JM99606BP130

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Oligo(furan=2,5=diylvinylene)s as n-conjugating spacers in linearly extended hybrid tetrathiafulvalene analogues El Hadj Elandaloussi," Pierre Fr&re,*" Amina Benahmed-Gasmi,".b AmCdCe Riou," Alain Gorguesa and Jean Roncali**" "Inginierie Moliculaire et Matiriaux Organiques, CNRS EP 66, Universiti d 'Angers, 2 Bd Lavoisier, 49045 Angers, France bLaboratoire de Chimie Organique, Universitd d 'Oran ES-SENIA, 31 000, Algirie The synthesis of a new series of push-push systems based on furan-2,5-diylvinylene oligomers end-capped with 1,3-dithiol-2- ylidene electron-releasing groups is described. 'H NMR spectroscopy and X-ray diffraction reveal that the molecules adopt a planar conformation stabilized by strong intramolecular interactions. Electronic absorption spectroscopy indicates that the effective conjugation length increases steadily with the length of the n-conjugated system without any evidence of saturation. Analysis of electrochemical behaviour by cyclic voltammetry shows that, whereas all compounds are easily oxidized into stable dications, with extension of the conjugation length the oxidation process progressively evolves from two successive one-electron steps to a single step two-electron transfer. Linear n-conjugated oligomers end-capped with 1,3-dithiol-2- ylidene units are the subject of much current interest.'-7 While initially developed as precursors of conducting cation-radical salts in the general frame of spatially extended tetrathiafulva- lene analogue^,^,^ recent years have witnessed a wide diversifi- cation of the potential applications of these systems as small bandgap molecular semiconductors," or as building blocks in push-pull or push-push molecules for quadratic or cubic nonlinear optics.''-18 From this viewpoint, it is clear that the properties of the final molecule will be determined largely by the nature of the n-conjugating spacer group.During the past few years, a great variety of n-conjugating structures have capped with 1,3-dithiol-2-ylidene electron-releasing groups (F,V,a-d). In the short-hand notation used, F, refer to the number of furan rings in the spacer and V, to the number of double bonds, while a-d refer to the R substituents of the 1,3-dithiole ring. The geometry of these compounds has been characterized by 'H NMR spectroscopy and X-ray diffraction and the relationships between their structure and their optical and electrochemical properties are discussed.been developed including acetylenic,12 ethyleni~'*~.~~-~~ and (hetero-) aromatic groups.2-6i10,1'~'6-20 Although polyalkenic spacers present high electron trans- mission effi~iency,~~,'~*~~ their lack of thermal and photochem- ical stability has been pointed out as a severe drawback.13v21 On the other hand, the efficiency of the more stable aromatic- and acetylenic-based systems appears limited by excessive charge c~nfinement.'~.~~ In this context oligo(aryleneviny1-ene)s, and in particular thiophene-2,5-diylvinyleneoligomers (nTVs), have progressively emerged as a good trade-off between the efficiency of polyethylenic systems and the stability of the polyaromatic one^.^^,^' We have recently reported the synthesis of push-push sys-tems based on nTVs end-capped with 1,3-dithiol-2-ylidene moieties.22 We have shown that, contrary to their analogues involving oligothiophenes (nTs), which are subject to interan- nular rotational disorder,' the lengthening of the n-conjugating spacer in nTVs-based systems does not lead to saturation of the effective conjugation.In addition to the synthesis of longer nTVs-based systems,23 an interesting development of this class of linearly .n-conjugated systems could involve replacement of the nTVs spacer by furan-2,5-diylvinylene oligomers (nFVs). This is interesting for two reasons.First, the smaller aromatic resonance energy of furan (0.70eV us. 1.26 for thi~phene)~~ will decrease the overall aromatic character of the spacer, which could allow a better electron delocalization over the whole n-conjugated system. Secondly, as already underlined, furaldehyde and furfuryl alcohol are much less expensive starting materials than their thiophene analogues and represent possible non-food appli- cations for agricultural product^.^' As a first step in this direction, we report here the synthesis of a new series of push-push systems based on nFVs end- Fa,b,d R a R = CaMe b R=SMe c R=Pr d R=H Results and Discussion Compounds Fa,b,d were prepared as previously described2 and diethyl 2-furylmethylphosphonate 2 was obtained in 68 % yield from the corresponding alcohol 1 via the bromomethyl derivative.26 Compounds F,V, were synthesized using the strategy shown in Scheme 1. E-1,2-Bis(2-furyl)ethene4 was obtained by McMurry coupling27 of furaldehyde 3 in 72% J.Muter. Chem., 1996, 6(12), 1859-1863 1859 1 2 &CHO0 111_ %L%cHo\I \I 3 4 5 6 7R=H 8R=CHO1 VII or VIIIv3:1 FSV2k Scheme 1 Reagents 1, PPh3, Br,-Et,O, 11, HPO(OEt),, NaH-THF, 111, TiCl,, Zn, iv, POCl,, DMF-DCE, v, BuLi, TMEDA, DMF-THF- hexane, vi, 2, Bu'OK, THF, vii, W, Et,N-THF, viii, P, BuLi-THF yield Formylation of 4 followed by Wittig-Horner olefination with 2 afforded compound 7 in 46% overall yield Dicarbaldehyde 6 was obtained in 46% yield by reaction of DMF with the dilithiated derivative of 4 prepared in the presence of N,N,N',N'-tetramethyldiaminoethane (TMEDA) Vilsmeier bisformylation of 7 using a large excess of reagent (4 equiv) gave the dicarbaldehyde 8 in 71% yield The trans configuration of 8 is clearly confirmed by the 3J 15 Hz coupling of the 'H NMR spectral signal of the ethenic protons Finally, Wittig or Wittig-Horner bis-alkenation of dicarbaldehydes 6 or 8 with Akibas' reagents W, or Pb,28-30afforded compounds F,Vla-c and F,V,a-c in 65-90% yields Compound F2Vld was obtained in 20% yield by thermal demethoxycarbonylation of F,V,a in hexamethylphosphoramide (HMPA) in the pres- ence of LiBr.H,O (Scheme 2) ' All F,V, compounds were obtained as single isomers The 'H NMR spectral signals of the ethenic protons of compounds F3V2,,c give an AB system with a 16 Hz 3J coupling which confirms the trans configuration, whereas for F,V, compounds a singlet was observed X-Ray structure determination of F,V,d confirms the trans configuration of the ethenic linkage, while the 134" angle between the plane of the furan nng and that of the dithiole Scheme 2 Reagents 1, HMPA, LiBr.H,O 1860 J Mater Chern, 1996, 6(12), 1859-1863 Fig.1 ORTEP view of F,Vld, H atoms omitted, ellipsoids drawn at 2 5% probability level ring shows that the molecule adopts a planar conformation (Fig 1) Furthermore, the crystal structure reveals that each end of the molecule adopts a syn conformation stabilized by strong S 0 intramolecular interactions The non-bonded contact [d=2 88(1)A] is shorter thay the sum of S and 0 van der Waals radii (18.+ 15 =3 3 A), but larger than a covalent S-0 bond (1 75 A) Such interactions between the sulfur atoms of a 1,3-dithiole ring and the oxygen or sulfur atom of an adjacent heterocycle have already been observed Table 1 lists the main electronic absorption data for F,V, compounds For each n value, the absorption maximum (Amax) exhibits a marked dependence on the nature of the substituent grafted at the 1,3-dithiole ring (R) Thus, for F2Vld, substitution of hydrogen by the electron-withdrawing C0,Me group to give F,Vla produces a blue shift of A,,, from 470 to 460nm, whereas introduction of electron releasing groups such as SMe (F,V,b) or propyl (F,Vlc) leads to the opposite effect, with a bathochromic shift of A,,, to 476 and 477nm, respectively On the other hand, Fig 2 and the data in Table 1 show that, independently of R, the lengthening of the spacer group produces as expected a red shift of A,,, Thus for compounds b, insertion of one (F,V,b) or two (F,V,b) FV units leads to a red shift of La,from 441 to 476 nm and 502 nm, respectively These results indicate that, in contrast to nTs-based systems,' the use of nFVs conjugating spacers does not lead to saturation of the effective conjugation, in agreement with the results obtained for their nTVs analogues 22 The cyclic voltammetry data of F,V, are listed in Table 2 As expected, the electrochemical behaviour depends on R and on the length of the nFV spacer group Thus, for F,V, compounds, replacing the electron-withdrawing C02Me group with the electron-releasing propyl group produces a consider- able negative shift of the first anodic peak potential (Epal)from 0 48 to 0 18 V Unlike what might be expected from optical data, replacement of hydrogen by SMe in the F1 and F2Vl series induces a 100-170 mV positive shift of Epal Such behaviour is commonly observed in the TTF series where alkylsulfanyl groups decrease n-donor ability 32 Table1 UV-VIS spectroscopic data for compounds Fa, b, d and F,V,a-d in CH,Cl, compound Laxlnm 402,425 421,441 411,437 460 476 470 477 501 508 340 380 420 460 500 540 580 Alnm Fig.2 UV-VIS spectra of (a) F,V,b and (b) F3V2bin CH2C1, Although insertion of an additional FV unit into F, com-pounds leads to a negative shift of Epal,the magnitude of this shift depends strongly on R. Thus, whereas for R =COzMe E,, shifts by 0.16 V from 0.64 to 0.48 V, this negative shift, which is only of 0.08 V for R=SMe, vanishes for R=H, and Fd and F,V1d show the same Epalat 0.23 V. A further extension of the length of the FV spacer does not lead to a further decrease of Epa,but, in contrast, to a 10-20 mV positive shift. Such behaviour, already observed for the parent compounds containing ethenic' or nTVsZ2 spacers suggests, in agreement with previous theoretical conclusions, that in these extended n-conjugated systems, the major contribution to the HOMO level arises from the 173-dithiole ring, while the length of the spacer essentially affects the LUMO level.Attempts to confirm this conclusion by recording the reduction potential of the compounds have until now remained unsuccessful, and perhaps further theoretical work could contribute to a more detailed understanding of this point. The CV of Fa exhibits two reversible one-electron oxidation steps corresponding to the successive generation of the cation radical and dication [Fig. 3(u)]. The difference between the two anodic peak potentials (Epa2-Epal) decreases from 220 mV for Fa to 170 and 80 mV for respectively Fb and Fd (Table 2), indicating that the increase of the electron-releasing effect of R leads to a reduction of the coulombic repulsion between positive charges in the dication.Extension of the conjugation length leads to a significant decrease of Epa2-Epal and, as shown by the CV of F2V,b [Fig. 3(b)],the two successive one-electron oxidation steps draw closer together, with a first anodic shoulder at 0.48 V followed by a main reversible oxidation wave peaking at 0.57 V. Although the proximity of these two waves does not allow a direct determi- nation of Epa2-Epal,measurement of the peak width at half maximum (PWHM) and application of the Nicholson and Myers treatment33 gave a value for Epa2-Epal of 110 mV. Whereas the CV of all other F,V, compounds display only a single reversible oxidation wave, determination of the PWHM for the F2Vl series gives values of 60 mV for F2V,b and 45 mV for F2Vlc and d (Table 2).These values, slightly larger than the 28.5 mV expected for an ideal two-electron transfer, suggest that the oxidation process involves two very close one- electron steps (Epa2 -Epal =10 mV) rather than a true two- electron transfer. In contrast, the 30 mV PWHM and zero value of Epaz-Epal obtained for the longest F3V2 series unequivocally show that these compounds are directly oxidized into their dicationic state through a single-step two-electron transfer. Furthermore, as shown in Fig. 3(c), this two-electron wave is followed by a reversible one-electron oxidation peak at 0.96 V and by a less reversible peak at 1.42 V. While the limited potential window of the used electrolytic medium does not allow a definitive assignment of this last peak to the formation of the tetracation, these results clearly show that the tricationic state of F,V2 compounds can be reached at rather moderate potential (cu.1.0 V us. SCE). Conclusion New linearly extended push-push molecules built around oligo(f~ran-2~5-diylvinylene)conjugating spacers have been synthesized. These compounds adopt a trans planar geometry and an increase in the length of the spacer produces the expected red shift of absorption without evidence for satu- ration. Extension of the conjugation length leads to an increase of the number of accessible redox states, allowing the direct formation of stable dications at low potentials.The analysis of the third order non-linear optical properties of these com- pounds is now under way and will be reported in future publications. Experimental Electrochemical experiments were carried out with a PAR 273 potentiostat-galvanostat in three-electrode single compartment cells. All potentials are referenced to the saturated calomel electrode (SCE). Cyclic voltammetry was performed using Pt microelectrodes of 7.85 x cm2 area and a Pt wire counter electrode. Oxidation potentials were determined from dichloro- methane solutions (HPLC grade) containing M substrate and lo-' M tetrabutylammonium hexafluorophosphate (TBHP) (Fluka puriss). Solutions were deaerated by nitrogen bubbling prior to each experiment which was run under a nitrogen atmosphere.Diethyl 2-furylmethylphosphonate 2 was obtained from 2- furylmethanol 1 using a known pr0cedu1-e.~~ E-1,2-Bis( 2-fury- 1)ethene 4 was prepared by McMurry coupling of furaldehyde. Compound 5 was prepared by formylation of 4 and purified by column chromatography (silica gel, CH,Cl,) giving yellow crystals (53%), mp 75°C; MS (EI) m/z 188 (M'; 100%); 6, [270 MHz, (CD3),SO] 9.53 (s, lH, CHO), 7.77 (s, lH, furan- Table 2 Electrochemical data for FVn" 0.64 0.86 220 0.40 0.57 170 0.23 0.31 80 0.48' 0.57 110 0.32 60 40' 1.35 0.23 45 1oc 1.30 0.18 45 10' 1.35 0.33 30 0 1.1 1.42 0.25 30 0 0.96 1.40 "Samples, M in 0.1 M Bu4NPF6-CH2C1,. Scan rate 100mV s-'. 'Shoulder. "Calculated by Myers and Shain's method (ref.33). J. Mater. Chem., 1996,6( 12), 1859-1863 1861 I I 000 025 050 075 1.00 0.00 0.25 EN Fig. 3 Cyclic voltammograms of (a)Fa, (b) F,V,b and (c) F,V,c Samples 100mV s-' H), 7 56 (d, lH, 3J 3 8 Hz, furan-H), 7 17 (d, lH, 3J 16 0 Hz, =CH), 6 89 (d, lH, 3J 160 Hz, =CH), 6 86 (d, lH, 3J 3 8 Hz, furan-H), 6 75 (d, lH, 3J 3 3 Hz, furan-H), 6 59 (dd, lH, 3J 3 8 and 3J 3 3 Hz, furan-H), v,,,(KBr)/cm-' 1660 cm-I (C=O), 1611 (C=C) E-1,2-Bis( 5-formyl-2-fury1)ethene 6 Butyllithium (1 6 M in hexane, 48 mmol) was added dropwise to a stirred solution of 4 (20 mmol) and TMEDA (48 mmol) in 100 ml THF-hexane (1 1) at room temperature The mix- ture was refluxed for 30 min, cooled to 40 "C and DMF (10 ml, 130 mmol) was added dropwise After 30 min stirring at ambi- ent temperature, the mixture was hydrolysed with 05~ HCl and extracted with CH2C1, The organic phase was washed with water and dried over MgS04 After removal of the solvent, the solid residue was washed with CC14 and recrys- tallized from chloroform giving 2 06 g (47%) of brown powder, mp 244"C, MS (EI) m/z 216 (M+, loo%), 6H[(CD3)2S0] 9 59 (s, 2H, CHO), 7 60 (d, 2H, 3J 3 8 Hz, furan-H), 7 26 (s, 2H, =CH), 7 03 (d, 2H, 3J 3 8 Hz, furan-H), 6c[(CD3)2SO] 178 0, 156 4,151 9, 118 2,114 0,108 4, vmX (KBr)/cm-l 1665 (C=O) E,E-2,5-Bis [ 242-furyl )vinyl] furan 7 To a stirred solution of 5 (094 g, 5 mmol) and diethyl 2- furylmethylphosphonate 2 (1 1 g, 6 mmol) in 30 ml dry THF, ButOK (0 73 g, 6 5 mmol) was added portionwise under N, After 40min stirring at room temperature the mixture was poured into 30ml water and extracted with CH2C12 The organic phase was washed with water, dried (MgS04) and evaporated under reduced pressure Column chromatography (silica gel, CH,C12) and recrystallization from hexane gave 1 1 g (87%) of brown powder, mp 104"C, MS (EI) m/z 252 (M+, loo%), hH (CDC13) 7 42 (d, 2H, 3J 1 65 Hz, furan-H), 6 94 (d, 2H, 3J 16 0 Hz, =CH), 6 81 (d, 2H, 3J 16 0 Hz, =CH), 6 45 (dd, 2H, 3J 3 3 and 3J 1 65 Hz, furan-H), 6 39 (d, 2H, 3J 3 3 Hz, furan-H), 6 36 (s, 2H, furan-H), G,(CDCl,) 1530, 152 6, 1422, 1148, 1144, 111 8, 111 6, 1089 1862 J Muter Chem, 1996, 6(12), 1859-1863 I I I 11 I 0.00 0.50 1.00 1.50 0.50 0.75 M in 0 1 M tert-butyl hydroperoxide (TBHP)-CH,Cl, Scan rate E,E-2,5-Bis [2-(5-formyl-2-fury1 )vinyl J furan 8 To a stirred solution of 7 (0 504 g, 2 mmol) and DMF (0 77 ml, 10 mmol) in 20 ml 1,2-dichloroethane, POC13 (30 ml, 48 mmol) was added dropwise and the mixture was refluxed for 3 h The mixture was cooled, hydrolysed with 3 M aqueous NaOAc and extracted with CH2Cl, The organic phase was washed with water and dried over MgSO, After removal of the solvent, the solid residue was recrystallized from chloroform to provide 0 44 g, (71%) of red powder, mp 183 "C, MS (EI) m/z 308 (M+, loo%), SH(CDC13) 7 24 (d, 2H, 3J 3 8 Hz, furan-H), 7 10 (d, 2H, 3J 16OHz, =CH), 690 (d, 2H, 3J 160Hz, =CH), 653 (d, 2H, '.I38Hz, furan-H), 651 (s, 2H, furan-H), h,(CDC13) 176 8, 158 1, 152 8, 151 7, 123 9, 119 3, 114 8, 113 9, 111 4, vmaX (KBr)/cm-' 1671 (C=O), 1620 (C=C) Compounds F,V,a-d and F,V,b,c Compounds F,V, and F3VZwere prepared by Wittig or Wittig- Horner reaction at 0°C with the corresponding ylide or phosphonate anions using a literature procedure 22 1,2-Bis(5-[ 4,sbis (methox ycarbon yl)-2H- 1,3-dithiol-2- ylidenemethyl]-2-furyl)ethene F,V,a Recrystallized from CHC13 (65%), brown powder, mp 255 "C (dec ), MS (EI) m/z 620 (M', 100%) (Found C, 5034, H, 325 Calc for C2&I2001oS4 C, 50 32, H, 3 22), GH[(CD3)2S0] 6 77 (s, 2H, =CH), 6 71 (s, 2H, S2C=CH), 6 69 (d, 2H, 'J 3 6 Hz, furan- H), 6 31 (d, 2H, 3J 3 6 Hz, furan-H), 3 87-3 86 (2s, 12H, Me0,C) 1,2-Bis(5-[ 4,5-bis(methylsuIfanyl)-2H-1,3-dithiol-2-ylidenemethyl]-2-furyl)ethene F2Vlb Recrystallized from CHC1, (go%), red-orange powder, mp 156°C (dec), MS (EI) m/z 572 (M+, loo%), hH[(CD3),SO] 6 75 (s, 2H, =CH), 6 70 (s, 2H, S,C=CH), 6 68 (d, 2H, 3J 3 5 Hz, furan-H), 6 34 (d, 2H, 3J 3 5 Hz, furan-H), 2 49-2 45 (2s, 12H, SMe) 1,ZBis[5-( 4,5-dipropyl-2H-l,3-dithiol-2-ylidenemethyl)-2-furyllethene FzVlc.Recrystallized from CHC1, (50%), red powder, mp 139°C (dec.); MS (EI) m/z 556 (M'; 100%); ~H[(CD~)~SO]6.70 (s, 2H, =CH), 6.66 (s, 2H, S,C=CH), 6.62 (d, 2H, 3.5 Hz, furan-H), 6.30 (d, 2H, 3.5 Hz, furan-H), 2.44-2.34 (m, 8H, 4 CH,), 1.67-1.51 (m, 8H, 4 CH,), 1.03-0.92 (m, 12H, 4 CH,). 2,5-Bis (2-{5-[4,5-bis(methylsulfanyl)-2H-1,3-dithiol-2-ylidenemethyll-2-fury1 )vinyl )furan F3V2b.Recrystallized from CHC1, (88%), red powder, mp 170°C (dec.); MS (FAB') m/z 664 (M+; 100%) (Found: C, 50.38; H, 3.58. Calc. for C2sH2403Ss: c, 50.61; H, 3.64); dH(CDC13) 6.87 (d, 2H, 15.7 Hz, =CH), 6.75 (d, 2H, 15.7 Hz, =CH), 6.40-6.37 (m, 4H, furan-H), 6.35 (s, 2H, S2C=CH), 6.16 (d, 2H, 3.3Hz, furan-H), 2.49-2.45 (2s, 12H, 4 MeS). 2,5-Bis{2-[ 5-( 4,5-dipropyl-2H-l,3-dithiol-2-ylidenemethyl)-2-furylI viny1)furan F3V2c. Chromatographed (silica gel, CH,Cl,) (76%), red powder, mp 118°C (dec.); MS (FAB+) m/z 648 (M'; 100%) (Found: C, 66.62; H, 6.63. Calc. for C36H4003S4:C, 66.65; H, 6.22); G,(CDCl,) 6.85 (d, 2H, 15.7 Hz, =CH), 6.74 (d, 2H, 15.7 Hz, =CH), 6.39 (d, 2H, 3.3 Hz, furan-H), 6.35-6.34 (2s, 4H, 2 furan-H and 2 S,C=CH), 6.13 (d, 2H, 3.3 Hz, furan-H), 2.44-2.34 (m, 8H, 4 CH,), 1.67-1.51 (m, 8H, 4 CH2), 1.03-0.92 (m, 12H, 4 CH,).1 ,2-Bis [5-(2H-1,3-dithiol-2-ylidenemethyl)-2-furyl]ethene FzVld. A solution of F,V,a (0.34 g) and LiBr (1.14 g) in HMPA (15 ml) was warmed for 1h at 90 "C, then for 20 min at 120 "C. The mixture was poured into 60 ml water and extracted with CH,Cl,. After drying over MgSO,, the solvent was evaporated under reduced pressure and the residual oil was purified by column chromatography (silica gel, CH2Cl,) to provide a red solid that was recrystallized from CHCl, (42%), mp 224°C (dec.); MS (EI) m/z 388 (M'; 100%); i5H[(CD3)2S0] 6.81-6.78 (m, 4H, SCH=), 6.74 (s, 2H, =CH), 6.55 (s, 2H, S2C=CH), 6.62 (d, 2H, 3J 3.5 Hz, furan-H), 6.26 (d, 2H, 3.5 Hz, furan-H). X-Ray diffraction Crystals of F,V,d were obtained from CHC1, solution. A single crystal (0.8 x 0.5 x 0.1) was mounted on an Enraf-Nonius CAD4-MACH3 diffractometer with graphite monochromator and Mo-Ka radiation at T=294 K.Unit cell parameters were known from a least-square analysis of 25 reflections. Crystal data. C18H12S402bM =388.55, orbhorhombic, Pb~u, U= 12.158 (6), b=7.939 (6) A, c 18.803 (5) A, I/= 1815 (4) A,, 2=4, F(000)=800, ,~=3.442cm-~,D,=1.42$)g~m-~, A= 0.71069 A. Data collection. The data collection was by the zig-zag 428 scan technique, 2.0 <8<30, t,,, =40 s, range HKL (0<H <11; 0 <K <17; -26 <L <26), intensity controls without appreci- able decay (0.2%) gives 5354 reflections from which 674 independent were measured with I >3a(I), Rint=2.0%.Structure refinement. After Lorentz and polarization correc- tions the structure was solved with Direct Methods (SIR) which reveal all the non-hydrogen atoms. After anisotropic refinement, the hydrogen atoms were found from hydro pro- grams. The whole structure was refined by the full-matrix least-square techniques (use of F magnitude; x, y, z, Pij for S, C and 0 atoms; x, y, z for H; 127 variables and 674 obser- vations; o=l/c~(F~)~=[a2(I)+(0.04 F02)2]-1/2) with the resulting R =0.066, Rw =0.071. Atomic coordinates, thermal parameters, and bond lengths and angles have been deposited at the Cambridge Crystallographic Data Centre (CCDC). See Information for Authors, J.Mater. Chem., 1996, Issue 1. Any request to the CCDC for this material should quote the full literature citation and the reference number 1145/12. References 1 T. Sugimoto, H. Awaji, I. Sugimoto, Y. Misaki, T. Kawase, S. Yoneda and Z. Yoshida, Chem. Mater., 1989,1,535. 2 A. Benahmed-Gasmi, P. Frere, B. Garrigues, A. Gorgues, M. Jubault, R. Carlier and F. Texier, Tetrahedron Lett., 1992, 33, 6457. 3 T. K. Hansen, M. V. Lakshmikantam, M. P. Cava, R. E. Niziurski- Mann, F. Jensen and J. Becher, J. Am. Chem. SOC., 1992,114,5035. 4 J. Roncali, M. Giffard, P. Frere, M. Jubault and A. Gorgues, J. Chem. SOC., Chem. Commun., 1993,689. 5 J. Roncali, L. Rasmussen, C. Thobie-Gautier, P. Frere, H. Brisset, M. Sallt, J. Becher, 0. Simonsen, T.K. Hansen, A. Benahmed- Gasmi, J. Orduna, J. Garin, M. Jubault and A. Gorgues, Adu. Mater., 1994,6, 841. 6 K. Takahashi, T. Nihira, M. Yoshifuji and K. Tomitani, Bull. Chem. SOC. Jpn., 1994,66,2330. 7 Y. Misaki, N. Higuchi, H. Fujiwara, T. Yamabe, T. Mori, H. Mori and S. Tanaka, Angew. 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M. Cai and A. K-Y. Jen, J. Chem. Soc., Chem. Commun., 1994,1689. 19 S. Gilmour, R. A. Montgomery, S. R. Marder, L-T. Cheng, A. K-Y. Jen, Y. Cai, J. W. Perry and L. R. Dalton, Chem. Mater., 1994,6, 1603. 20 M. Blanchard-Desce, C. Runser, A. Fort, M. Barzoukas, J. M. Lehn, V. Bloy and V. Alain, Chem. Phys., 1995,199,253. 21 H. Gibson and J. Pochan, Macromolecules, 1991,24,4834. 22 E. Elandaloussi, P. Frkre, J. Roncali, P. Richomme, M. Jubault and A. Gorgues, Adv. Mater., 1995,7,390. 23 E. Elandaloussi, P. Frere and J. Roncali, Tetrahedron Lett., in the press. 24 J. March, Advanced Organic Chemistry, Wiley, New York, 1985, p. 42. 25 U. Schobert, J. Salbeck and J. Daub, Adu. Mater., 1992, 4,41. 26 H. Seeboth and S. Andreae, Z. Chem., 1977,16,399. 27 J. E. McMurry, Chem. Rev., 1989,89,1513. 28 K. Akiba, K. Ishikawa and N. Inasoto, Bull. Chem. SOC. Jpn., 1978, 51,2674. 29 T. K. Hansen, M. V. Lakshmikantham, M. P. Cava, R. M. Metzger and J. Becher, J. Org. Chem., 1991,56,2720. 30 A. J. 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ISSN:0959-9428    

DOI:10.1039/JM9960601859

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Preparation and properties of epoxidized natural rubber/poly (8-caprolactone) self-vulcanizable blends Yasuhisa Tsukahara,"' Tomio Yonemura,' Azanam Shah Hashim,b Shinzo Kohjiya' and Kyoji Kaeriyama" aDepartment of Materials Science, Kyoto Institute of Technology, Kyoto 606, Japan bPusat Pengajian Technology Industry, University Sains Malaysia, Penang, Malaysia 'Institutefor Chemical Research, Kyoto University, Uji 611)Japan Curing behaviour as well as mechanical properties of the binary blends of epoxidized natural rubbers (ENR) with end- carboxylated telechelic poly(ecapro1actone)s (XPCL) has been investigated for development of high-performance self- vulcanizable rubber blends. The binary blends of ENR with different degrees of epoxidation and XPCL of different molecular masses were prepared by using an open two-role mill and subsequently cured at 160-200 "C.It was found that the end-functional and crystallizable XPCLs cured ENR well in the absence of other additives and acted as an effective polymeric crosslinker for ENR to produce self-vulcanizable binary blends. The degree of chemical crosslinking depended on the degree of epoxidation of the ENR as well as the curing time and temperature. The relative contribution of the physical crosslinking via crystallization of poly(E-caprolactone) chains to that chemical crosslinking was controlled by the molecular mass of the XPCL to give elastomeric materials with various stress-strain curves. End-functionalized oligomers or polymers such as macromono- mers'.' and telechelic polymers334 have recently attracted much attention as useful building blocks for the development of high-performance polymeric materials. Utilization of telechelic polymers as one component in polymer blends might be interesting to achieve the reactive blending of two different polymers, in which desired properties associated with the telechelic polymers and the crosslinking points between the two components could be introduced simultaneously. Among many polymer pairs, a telechelic poly (E-capro- lactone)/epoxidized natural rubber pair might be interesting.Poly (E-caprolactone), a tough, crystalline polymer of moderate melting point, possesses the unique ability of being miscible with a variety of other polymers over a wide composition range.5,6 Epoxidized natural rubber (ENR) is a useful rubber material since the presence of the oxirane groups make it possible to perform various types of crosslinking reactions in addition to normal sulfur vulcanization through the double In addition, the presence of the oxirane group in natural rubber (NR) leads to its polar nature and the resulting ENR shows various useful properties depending on the degree of epoxidation, e.g.oil resistance, low gas permeability, and good adhe~ion.~*'~9'~ Since poly(s-caprolactone) is a biodegrad- able polyester and ENR is based on a natural polymer, their binary blends should also be biodegradable and thus useful as ecornaterial~.~~~'~ In this study, we report the experimental finding that blending of the telechelic dicarboxylated poly(ecapro1actone) (XPCL) into ENR and subsequent compression molding at elevated temperature cured ENR well in the absence of any other additives.This was clearly shown in the curing behaviour of the binary blends of the telechelic XPCL with ENR as well as the thermal and mechanical properties of the blends after the curing reaction.16 Generally, vulcanization of rubbers requires many additives in addition to sulfur as a crosslinking reagent, e.g. assisting reagent, accelerator, retarder, stabilizer, and so on. In contrast to this, our result indicates that simple blending of the telechelic XPCL and molding cures ENR well and the resulting blends show good elastomeric properties.This indicates that telechelic polymers are very useful for the preparation of self-vulcanizable blend materials. Experimental Samples of 50 and 25% epoxidized natural rubbers (ENR5O and ENR25), were supplied from Guthrie Co. Malaysia. Epoxidation of the isoprene units of the latex form of the natural rubber was performed by reaction with performic or peracetic acid.'-3 Dicarboxylated telechelic poly(8-caprolactone)s (XPCL)s of different molecular masses were prepared by reaction of the terminal hydroxy groups of poly(e- capro1actone)s (PCL)s (Daicel Co. Ltd., Japan) with phthalic anhydride in the presence of triethylamine and 4-dimethylamin- opyridine in tetrahydrofuran according to Scheme 1. After reaction, the XPCLs were purified by extraction to remove unreacted phthalic anhydride.The introduction of the carboxy- phenyl end-groups was confirmed by 'H NMR spectroscopy and gel permeation chromatography (GPC) using refractive index and UV detectors. 'H NMR spectra were measured on a Varian Gemini-200. The molecular masses of the XPCLs were determined by GPC using the standard polystyrene calibration curve. GPC was performed with chloroform as eluent at 35°C using a Tosoh HLC-802A instrument with G3000H and G5000H columns. XPCL Scheme 1 Preparation of XPCLs J. Muter. Chem., 1996, 6(12), 1865-1870 1865 Table 1 End-carboxylation of PCLs" sample PCLb/mmol -OH/mmol PTAc/mmol DMAPd/mmol TEA'/mmol THFf /ml XPCL 1000 25 0 50 0 250 0 41 7 291 7 500 XPCL2OOo 20 0 40 0 200 0 33 3 233 3 500 XPCL4OOo 12 5 25 0 1250 20 9 145 9 500 a Reaction tme 48 h, temperature 66"C a,w-Dihydroxypoly(&-caprolactone)Phthalic anhydnde 4-Dimethylaminopyridine Triethylamine Tetrahydrofuran The binary blend compounds of ENR and XPCL (or PCL) were prepared by using an open two-roll mill at room tempera- ture (20 "C) under circulation of cooling water These com- pounds were aged overnight, and then the curing behaviour of the compounds was monitored by time-torque curves at 160-200°C using a Curelastometer I1 (JSR Co Ltd) Using the cure curves as a guide, the compounds were cured at 180 "C for fixed times under a pressure of 100 kgf cm-2 (kgf= 980665N) using a hot-press machine to produce the ENR-XPCL (or PCL) blend sheet specimens Differential scanning calorimetric (DSC) curves, and dynamic and tensile mechanical properties of these blend specimens were measured :on a Seiko SSC-580/DSC-20, Rheology DVE-V4 rheospectro-65 60 55 50 45 meter and a Shinkotsushin Kogyo TCM-100 tensile testing elution count machine, respectively Electron microscopic photographs of ultrathin sections of the specimens were taken by using a Fig.1 GPC curve of XPCL4000 taken by RI and UV detectors, JEOL JEM1200EX-I1 instrument after staining with OsO, chloroform, 35 "C, one count is ca 1 ml Table 3 Blend ratios of ENR/XPCL and ENR/PCL binary blend Results and Discussion compounds' Dicarboxylated telechelic PCL (ENR/XPCL) 100 100 100 100 100 100The end-group transformation of the hydroxy PCL to XPCL ENR5O ----XPCLlOoo 30 -was carned out with an excess of phthalic anhydnde under XPCL2000 -30 ----the conditions shown in Table 1 'H NMR spectra of the XPCL4000 --20 30 40 50 XPCLs showed new aromatic proton signals of the carboxy- ENR-25 100 100 100phenyl end groups at 6 7 25-7 90 as well as a large decrease XPCLl000 30 --of the methylene proton signal intensity connected to the end XPCL2000 -30 ---30hydroxy group of PCLs at 6 3 32 The end-group functionality XPCL4000 of XPCLs estimated from the peak intensity of 'H NMR (ENR/PCL) spectra were 70-100% as shown in Table 2 together with the ENRSO 100 100 100 -molecular mass and the polydispersity index (M,/M,) deter-PCLlOOo 30 -PCL2Ooo -30 -mined by GPC Fig 1 shows the GPC curve of XPCL4000 as PCL4Ooo --30an example GPC curves of XPCLs detected by an RI detector showed almost equivalent behaviour to that obtained with a "Compounds were prepared using an open two-roll mill at roomUV detector, indicating the uniform introduction of the car- temperatureboxyphenyl end group XPCLs at 180 "C were homogeneous, but the ENR-PCL sheetsCuring behaviour prepared under the same conditions showed rather hetero- Blend ratios of the compounds prepared by an open two-roll geneous appearance and were not cured well This indicates mill are shown in Table 3 The blend compounds of ENR with that ENR can be well cured by telechelic dicarboxylated PCLs the original PCLs were also prepared for comparison The but not by dihydroxy PCLs time-torque curves of ENR-XPCL binary blend compounds Fig 2 shows the effect of the molecular mass of the XPCL without any other additives at 160-200°C showed a large component on the cure curves measured for ENRSO-XPCL torque increase after very short induction period ( 1-2 min) (XPCL 30 phr, phr =per hundred rubber) blend compounds On the other hand, the ENR-PCL blend compounds did not It is seen from Fig 2 that the period of the sharp torque rising show any torque increase in the time-torque curve and the region is almost unaffected by the molecular mass of the curve was almost the same as those of the green ENRs at the XPCL, however, the maximum torque (at 2 h) increases signifi- same curing temperature The hot-pressed sheets of ENR-cantly with decrease in molecular mass of the XPCL This corresponds to an increase in the crosslinking density due to Table 2 Characteristics of XPCLs the increase in the concentration of the end-functional groups with decreasing molecular mass Fig 3 shows the effect of GPC the cure temperature on the curing behaviour of (a) ENR50-XPCL4000 and (b) ENR25-XPCL4000 blend sample Mn Mw/M, fa compounds It is seen that the curing rate increases with increase in cure temperature The curing rates of XPCLlOoo 1300 2 04 140 ENR25-XPCLs [Fig 3(b)] are lower than those of the corre- XPCL2Ooo 2500 2 42 200 XPCL4Ooo 6400 175 152 sponding ENRSO-XPCLs [Fig 3(a)] Compounds containing ~~~ ~ ~ highly epoxidized ENR (ENRSO) exhibit higher torques at 'f =end group functionality estimated by 'H NMR spectroscopy comparable times relative to low epoxidized samples (ENR25), 1866 J Mater Chem, 1996,6(12), 1865-1870 lo+ 0 60 120 time/min Fig.2 Time-torque curves for ENRSO/XPCLs ( 100:30) blend com- pounds cured at 180°C: ---, XPCLlOOO ---, XPCL2000; -, XPCL4000 1.0 0.5 6 60 120 60 120 time/mi n Fig. 3 Effect of cure temperature on time-torque curves for (a) ENRSO/XPCLs ( 100:30) blend compounds and (b) ENR25/XPCLs (100:30) blend compounds. -, 160"C; ---,180 "C; ---, 200 "C indicating that the crosslinking formation is influenced by the degree of epoxidation in the ENR. It should be noted here that the end carboxylic groups provide an acidic environment which might cause cationic ring opening of the epoxy groups (furanization).This might depend on the molecular mass and the blend ratio of the XPCL. Further investigation on the crosslinking reaction will be discussed in a future paper. Thermal properties Poly(&-caprolactone) is a semicrystalline polymer and shows a melting point (T,) at ca. 50-60°C, and is slightly depen- dent on the molecular mass. Fig. 4 shows DSC curves for (a) ENRSO-XPCL ( 100:30) hot-pressed sheets and (b) ENR5O-PCL (100:30) sheets in the temperature range -100 to 100 "C (cure time is 14 min for all the samples). The glass transition (T,)of the ENR component is observed at the same temperature (ca. -20 "C) for all samples. This indicates that a phase-separated structure exists in these blends. However, the endothermic peak corresponding to T, of the XPCL component at ca.50-55°C differs considerably from those of the original dihydroxy PCL. T, peaks for ENR-PCL blends are sharp and the intensity is almost independent of the molecular mass of the PCL component. In contrast to this, 0Vc i A -100 -50 0 50 100 -100 -50 0 50 IOO temperature/"C Fig. 4 DSC thermograms for (a) ENRSO/XPCLs (---, XPCLlOOO;-.-, XPCL2000; -, XPCL4000) and (b) ENRSO/PCLs (---, PCL1000; -.-, PCL2000; -, PCL4000) binary blends. Heating rate: 10"C min-'. Cure time was 14 min and cure temperature was 180"C for all samples. the peak intensity is much reduced for ENR-XPCL blends and there is no T, peak for the blend XPCLlOOO of lowest molecular mass. The difference in the T, peak intensity between ENR-XPCL and ENR-PCL might be due to the existence of crosslinking points, which could restrict crystallization of the poly (&-caprolactone) chains.Mechanical properties Fig. 5 shows the temperature dependences of the dynamic mechanical modulus and the loss tangent for the ENRSO-XPCL (100: 30) blend sheets. It is seen that the large lowering of E' corresponding to Tgof the ENR component is observed at ca. -20 "C and there is a second reduction of E' due to the T, of XPCL component at ca. 50°C. The degree of the second reduction decreases significantly with decrease of molecular mass of the XPCL and for the XPCLl000 blend it is absent. The temperature dependences of loss tangent for XPCL4000 blend also show the corresponding maxima, but the second maximum is absent for the XPLClOOO blend.These results are consistent with the DSC measurements. It appears that the chain length of XPCLlOOO is too short to form crystalline domains under the restriction of the crosslinking points while the long XPCL4000 chains can form a substantial crystalline phase. Fig. 6 shows the effect of the molecular mass of XPCLs on -2L . ' ' . ' ' ' ' ' a * . ' ' * ' -100 -50 0 50 100 temperature/"(= Fig. 5 Temperature dependences of (a) dynamic storage modulus and (b) loss tangent for ENRSO/XPCLs (100:30) blend sheets. Cure time of the compounds was 14 min for all samples. ---, XPCLlOOO; -*-, XPCL2Ooo; -, XPCL4000. J.Muter. Chem., 1996, 6(12), 1865-1870 1867 0 100 200 300 400 strain (%) Fig. 6 Stress-strain curves for ENRSO/XPCL( 100 30) blend sheets measured (a) at room temperature (20 "C) and (b) in a hot water-bath (8OOC) Elongation rate lOOmmmin-' Cure time 14min for all samples ---, XPCLlOOO, --, XPCL2000, -, XPCL4000 the tensile stress-strain curves for the ENRSO-XPCL (100 30) blend sheets measured at (a) room temperature and (b) above T, of the poly(ecapro1actone) chain (8OOC) (cure time is 14 min for all the samples) It is seen that the modulus as well as the tensile strength (TB)and the elongation at break (EB) increases with increase in molecular mass of XPCLs Values of TB and EB as well as the stress at 50-600% elongation (M50-M600)are shown in Table 4 The increase in the modulus might be related to both the filler effect and the physical crosslinking of the crystalline phase of the XPCL component, since the effect of the crystalline phase becomes more prominent with increase in molecular mass of XPCLs as shown in Fig 4 and 5, while the extent of the chemical crosslinking through the end carboxy groups of XPCL and the epoxy groups decreases The stress-strain curves at 80°C [Fig 6(b)], show that the modulus increases in the order XPCL4000<2000 < 1000 above T,, indicating again that the Table 4 Tensile properties of ENRSO/XPCL (100/30) binary blends" sample XPCL- 1000 XPCL-2000 XPCL-4000 0 52 0 59 0 96 0 86 0 92 127 144 147 186 2 27 2 15 2 45 -3 17 3 35 --4 93 --8 77 2 57 11 48 325 400 645 "Cured at 180"C for 14 min 1868 J Muter Chew , 1996, 6(12), 1865-1870 degree of crosslinking formation increases with decrease of the XPCL chain length The marked increase in TB for ENR50-XPCL4000 [Fig 6(a)] might be related to strain-induced crystallization of the ENR component at large elongation The degree of the strain-induced crystallization would be expected to be reduced by an increase in the crosslinking density Large EBvalues are also due to the XPCL crystalline domains, which will be fragmented at large elongations, as will be discussed later, but still might be able to act as the physical crosslinking points to give large E, values Therefore, the good mechanical properties (increase in TB and EB)for ENR50-XPCL4000 [Fig 6(a)] might be ascnbed to the effect of the synergism of the physical crosslinking through the crystalline domains of poly(&-caprolactone) chains, the strain-induced crystallization of the rubbery component and the chemical crosslinking between the end carboxy groups and the epoxy groups The crystalline domains of XPCL4000 might reinforce the tensile properties of the blend Fig 7 compares the hysteresis and the permanent set in the stress-strain curves of ENRSO-XPCL (100 30) blend sheets during cyclic deformations up to 300% elongation It is seen that considerable hysteresis is observed in the blend with XPCL4000 The hysteresis as well as the permanent set decreases upon decreasing the molecular mass of the XPCL component and there is almost no hysteresis in the XPCLlOOO blend The observed hysteresis and permanent set might be ascribed to structural changes during elongation, especially the change of the crystalline domains of poly (s-caprolactone) 41 II --c 1st cycle 2nd .cH 3rd 12l0 XPCLlOOO +*2nd 1st cycle XPCL2000 4 +*2nd 1st cycle XPCL4000 I 0 100 200 300 400 strain (%) Fig.7 Effect of the molecular mass of XPCL on the elongation and recovery behaviours in the cyclic stress-strain curve at room temperature (20 "C) Elongation and recovery rate 100 mm min-' Table 5 Tensile properties of ENR/XPCL4000 (100/30) binary blends" l""'"'1 10 sample 0 500 strain (Yo) Fig.8 Influence of the degree of epoxidation and cure time on the stress-strain curves at room temperature (20 "C).Elongation rate: 100 mm min-'. ENRSO: -, 14 min; -.-, 60 min. ENR25: ..., 14 min; ___ ,60 min. chains, in which plastic deformation, destruction and fragmen- tation might occur by the large applied strain; fragmented small crystalline domains may, however, still be able to act as physical crosslinking points. Therefore, it is reasonable that the blend with XPCLlOOO did not show hysteresis because no crystalline phase was detected by DSC or by dynamic modulus measurements (Fig. 4 and 5). It is also seen from Fig. 7 that the hysteresis of XPCL4000 and 2000 blends in the second and third elongation cycles becomes very small and resembles that of the XPCLlOOO blend.This indicates that the crystalline domains are destroyed and fragmented by the first elongation resulting in the suppression of the effect of the crystalline domains and the blends show more elastic behaviour mostly through the chemical crosslinking points. Fig. 8 shows the effects of the degree of epoxidation of ENR as well as the cure time on the stress-strain curves for ENRSO and ENR25 blends with XPCL4000. These blends were cured for different times (14 and 60 min). The values of TB,EB and the stress at 50-800% elongation (A450-A4800)of these blend sheets are summarized in Table 5. The stress-strain curves of ENR25 blends show both lower modulus and lower TB but ENRSO ENR25 14 min 60 min 14 min 60 min 0.99 1.20 0.26 0.33 1.31 1.56 0.35 0.49 1.79 2.19 0.52 0.78 2.33 2.95 0.76 1.12 3.10 4.05 1.04 1.64 4.42 6.29 1.51 2.32 7.15 - 2.18 3.39 3.31 5.51 - - - 8.75 10.02 11.08 5.27 9.75 683 59 1 810 830 " Cured at 180"C.higher EB compared with those of ENR5O blends at the same cure time. Therefore, the use of less epoxidized ENR produces less rigid and more extensionable rubber materials. It is also seen that an increase in the cure time increases both the modulus and TBbut decreases EB. These are consequences of the change in the extent of the crosslinking reaction between the carboxy end-groups and the oxirane groups. Fig. 9 shows a transmission electron micrograph observed for an ultrathin section of the ENR50-XPCL4000 (100: 30) blend sheet, in which light islands of the poly(s-caprolactone) domain dispersed in the dark ENR matrix are seen.It is also observed that many long poly (s-caprolactone) crystalline lamellae grow into the rubbery matrix as light strips, the thickness of which is ca. 10 nm and uniform. Presumably, these crystalline lamellae play an important role in the reinforcement of the tensile mechanical properties of the ENR-XPCL4000 blend. Conclusion In conclusion, it was shown that the end-carboxylated telechelic XPCLs act as an effective polymeric crosslinker for ENR to produce the self-vulcanizable binary blends, which can be Fig. 9 Electron microphotographs of an ultrathin section of ENR50/XPCL4000 (100:30) blend cured at 180 "Cfor 14 min; stained with OsO,, magnification (a) x 5000, (b) x 30 000 J.Mater. Chem., 1996, 6(12), 1865-1870 1869 converted to elastomeric matenals by simple cunng at 160-200°C It was found that the degree of crosslinking between XPCL and ENR depended on the molecular mass of the XPCL and the degree of epoxidation in the ENR as well as the cure time and temperature It was also shown that the relative contnbution of the physical crosslinking to the chemi- cal crosslinking is controlled by the molecular mass of the XPCL to give various stress-strain curves This indicates that telechelic polymers are very useful for the preparation of a wide variety of self-vulcanizable blend materials Since poly(&- 3 4 5 6 7 8 9 ed M K Mishra, Polymer Frontier International, New York, 1994,p 161 Telechelic Polymers Synthesis and Applications, ed E J Goethals, CRC Press, Boca Raton, FL, 1989 Y Tezuka, Prog Polym Sci ,1992,17,471 J V Koleske and R D Lundberg, J Polym Sci A-2,1969,7,795 M Aubin and R E Prud’homme, Macromolecules, 1980,13,365 I R Geilling, Rubber Chem Technol, 1985,58,86 I R Geilling and N J Mornson, Rubber Chem Technol, 58,243 A S Hashim and S Kohjiya, Kautsch Gummi Kunstst, 46,203 985, 993, caprolactone) is a biodegradable polyester and ENR is based on a natural polymer, their binary blends could be also biodegradable and thus might be interesting as ecomaterials 10 11 A S Hashim and S Kohjiya, J Polym Sci, Polym Chem 1994,32,1149 S Jayawardena, D Reyx, D Durand and C P Pinazzi, Makr Chem .1984.185.19.2089 Ed , mol 12 C S L Baker, I R Geilling and P Newell, Rubber Chem Technol , The authors are indebted to Mr Y Fukui and Mr Y Ohtsuka 1985,58,67 of Daicel Chem Ind Co Ltd for supplying the hydroxy- terminated poly(&-capro1actone)s and for help in recording the electron microscopic photographs 13 14 15 R Alex, N M Mathew, P P De and S K De, Kautsch Gummi Kunstst ,1989,42,674 J E Potts, R A Clendinnmg, W B Ackart and W D Niegmh, ACS Polym Prepr ,1972,13,629 C G Pitt, F I Chasalow, Y M Klimas and A Schindler, J Appl References 16 Polym Sci ,1981,26,3779 Y Tsukahara, T Yonemura, A S Hashim, S Kohjiya, Polym Prepr Jpn , 1994, 43, 1298, International Rubber Conference 1 Y Yamashita and Y Tsukahara, in ModlJication of Polymers, eds (ZRC95Kobe),1995, p 74 C Carraher and J Moore, Plenum, New York, 1983, p 131 2 Y Tsukahara, in Macromolecular Design Concept and Practice, Paper 6/03150A, Received 7th May, 1996 1870 J Mater Chem, 1996, 6(12), 1865-1870

ISSN:0959-9428    

DOI:10.1039/JM9960601865

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

The synthesis and characterisation of a novel thiophene-based liquid crystal exhibiting ferro- ferri- and antiferro-electric phase types David J. Byron,' Lachezar Komitov,b Avtar S. Matham,*' Ian McSherry' and Rqbert C. Wilson' 'Department of Chemistry and Physics,. The Nottingham Trent University Clifton Lane Nottingham UK NG11 8NS bDepartment of Physics Chalmers University of Technology S-412 96 Goteborg Sweden The synthesis and liquid crystal properties of (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl5-( 4-decyloxyphenyl) thiophene-2- carboxylate is reported.. This material exhibits the following phase types ("C) I 97.4 SA 92.2 Sc* 81.4 ferri 78.8 antiferroelectric 48.6 glass state (characterised by thermal optical microscopy and differential scanning calorimetry). Results from electro-optical investigations for example field-induced transitions temperature and voltage dependence and current and electro-optic response clearly illustrate the presence of the Sc* ferro- ferri- and antiferro-electric phase types.Recently there has been considerable interest in the synthesis and liquid crystal properties of compounds which may exhibit antiferroelectric and ferrielectric in an attempt to promote the development of novel fast-switching electro-optic display devices. Chandani et aL4 reported the occurrence of such phases in MHPOBC 1 1 which are particularly important because they exhibit the phenomenon of tristate switching i.e. the electric field-induced phase transition between the antiferroelectric and ferroelec- tric phases.The structure of the antiferroelectric phase is regarded as a herringbone arrangement of molecules in which the molecules tilt in opposite directions in adjacent layers. Hence the overall spontaneous polarisation of the antiferroelectric phase averages to zero. However the structure of the ferrielectric phase is rather more complex. One possible situation may be such that the molecules in every third or fourth layer are tilted in the opposite direction to those in the remaining layers.. Thus the magnitude of the spontaneous polarisation in the ferri-electric phase is smaller than the one associated with the S,*(ferroelectric) phase. Investigation of the liquid crystal properties of thiophene- based heterocyclic compounds has shown that their properties are dependent on the linearity of the ~ystem.~-~ Hence thio- phene systems are generally lower melting than their analogous 1,4-phenylene counterparts due to a reduced packing efficiency of the molecules.In addition thiophene-based systems possess a strong lateral dipole within their structure which promotes negative dielectric anisotropy thus eliminating the need for lateral cyano and fluoro substituents which tend to increase the molecular breadth and possibly the viscosity of the system. Here we report the synthesis of (R)-(-)-4-( 1-methyl- heptyloxycarbonyl )phenyl 5-( 4-decyloxyphenyl) thiophene-2- carboxylate 2 2 in order to assess the validity of the 'bent' or relatively non-linear 2,5-disubstituted thiophene moiety as a suitable * Author for correspondence.mesogenic core capable of exhibiting the ferro- ferri- and antiferroelectric phase types. Synthesis The preparative route undertaken for the synthesis of (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl 5-( 4-decyloxypheny1)-thiophene-2-carboxylate 2 is outlined in Scheme 1. The Grignard reagent of 4-bromoanisole 3 was treated with an excess of trimethyl borate at -78 "C to afford the corre- sponding 4-methoxyphenylboronic acid 4. Commercial 2-bromothiophene was cross-coupled* with compound 4 in the presence of a catalytic amount of tetrakis( tripheny1phosphine)- palladium(0) to give 2-( 4-methoxyphenyl) thiophene 5 which was then demethylated with boron tribromide' to yield the intermediate hydroxy compound 6.Alkylation of 6 with 1-bromodecane followed by lithiation in the presence of N,N,N',N'-tetramethylethylenediame (TMEDA) and car-bonation of the intermediate alkoxy compound 7 gave the corresponding 5-( 4-decyloxyphenyl ) thiophene-2-carboxylic acid 8. The desired chiral phenol 13 was prepared uia a series of protection/deprotection" steps on 4-hydroxybenzoic acid 9 followed by esterification with (R)-(-)-octan-2-01. Alternatively compound 13 may also be prepared using analogous methods reported by Chin et al." which involve protection of 4-hydroxybenzoic acid with methyl chloroformate.. The thio- phene-based carboxylic acid 8 was esterified12 with compound 13 in the presence of 1,3-dicyclohexylcarbodiimide(DCC) and 4-dimethylaminopyridine (DMAP) as catalyst to afford the desired (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl 5-( 4-decyloxyphenyl) thiophene-2-carboxylate 2.Results and Discussion Optical microscopy differential scanning calorimetry and miscibility studies The liquid crystal transition temperatures and thermodynamic data for compound 2 are listed in Table 1. Phase identification was best achieved by compressing the sample between two pre-treated glass substrates (cell gap of approximately 4 pm) which causes the molecules to adopt homeotropic alignment. In this situation the SA phase appears as the homeotropic texture i.e. optically extinct when the sample is placed between crossed polarisers. At the SA-Sc* transition a dramatic textural change is observed whereby the dark homeotropic texture of the S phase gives rise to a blue J.Muter. Chem. 1996 6( 12) 1871-1878 1871 Reagents and conditions i Mg I THF then B(OMe) THF -78 "C; ii 2-bromothiophene Pd(PPh,) 2 M Na,CO reflux; iii BBr CH2C12 -78°C to room temp.; iv C,,H2,Br K2C03 acetone reflux; v TMEDA 1.6~ butyllithium then COz H'; vi BnBr K2C03,acetone reflux; vii aq. EtOH KOH reflux; viii (R)-(-)-octan-2-ol DCC DMAP CH2Cl,; ix H 10% Pd-C EtOH room temp.; x DCC DMAP CH2C12 Table 1 Liquid crystal transition temperatures and thermodynamic data for (R)-(-)-4-( 1 -methylheptyloxycarbonyl)phenyl5-(4-decyloxy-phenyl )thiophene-2-carboxylate 2 T/"C (AH/kJ mol-I)" I-SA SA-S,* S,*-Ferri Ferri-Anti Anti-Glass 97.4 92.2 81.4 78.8 48.6 (5.48) (0.60) (0.014) (-Ib (19.84) For each compound the first row gves transition temperatures and the second row (in parentheses) gives enthalpies of transition on cooling (DSC scan rate 1O'C min-').bThe enthalpy of the transition was too small to be evaluated. petal-like texture characteristic of the Sc* phase i.e. selective light reflection (Plate 1).. The blue coloration is indicative of a helical system which possesses an extremely short pitch (less than 0.3 pm) and a helix axis perpendicular to the sample plates.. The onset of the S,*(ferri) phase culminates in the appearance of an intense shimmering milky-white texture (Plates 2 and 3) associated with a substantial increase in the pitch.Similarly the S,*(ferri j-S,*(antiferro) transition was characterised by the loss of the shimmering texture which was superseded by the appearance of a red-brown (selective reflec- tion) coloration (Plate 4) indicative of the shortening of the pitch when compared to the ferrielectric phase. However 1872 J. Muter. Chem. 1996 6( 12) 1871-1878 Plate 1 Texture of a 4 pm thick sample of 2 with surface treatment for a homeotropic alignment at 85 "C [S,*(ferroelectric) phase] Plate 2 Texture of a 4 pm thick sample of 2 with surface treatment for a homeotropic alignment at 81 "C (just entering in the ferrie- lectric phase) Plate 3 Texture of a 4 pm thick sample of 2 with surface treatment for a homeotropic alignment at 79 "C [S,*(ferrielectrici phase] compared with the ferroelectric phase the pitch in the antiferroelectric phase is 10nger.I~ Study of these phase types by differential scanning calor- imetry (DSC) is difficult because of the small enthalpy associ- ated with the transitions hence some peaks may not be observed.However Fig. 1shows the DSC thermogram (second cool 10°Cmin-l) for compound 2 whereby the enthalpy of the SA-Sc*(ferro) transition is sufficiently large. measurable and corresponds to a first order transition (0.60 kJ mol-I). The peak corresponding to the S,*(ferro)-S,*(ferri) transition is rather small but nevertheless equates to a second-order Plate 4 Texture of a 4 pm thick sample of 2 with surface treatment for a homeotropic alignment at 75 "C [S,*(antiferroelectric) phase] Fig.1 DSC thermogram showing the second cool cycle for (R)-(-)-4-( 1-methylheptyloxycarbonyl )phenyl 5-( 4-decylox yphenyl )thiophene-2-carboxylate 2 recorded at 10"C min-' transition (0.014 kJ mol-'). Although the transition of the ferri-to the antiferro-electric phase was detected by DSC unfortunately it was too small to be evaluated with any great certainty.. This shows the importance of using complementary techniques i.e. thermal optical microscopy coupled with DSC as well as the behaviour of some important physical param-eters during phase identification. The existence of these phases was further confirmed by miscibility studies with (R)-(-)-1-methylheptyl 4'-(4-decyloxy-benzoyloxy)biphenyl-4-carboxylate 14 as the standard mate-rialI4 [transitions ('C) is0 123.7 SA 103.9 Sc* 91.7 ferrielectric 74.5 antiferroelectric 47.2 J*).14 The binary phase diagram for mixtures of compound 2 with the standard 14 is depicted in Fig. 2 and shows continuous miscibility across the entire composition range for the SA Sc* (ferroelectric) S,*(ferrielectric) and S,*(antiferroelectric) phases thus confirming the identification of the phases. Field-induced transitions temperature and voltage dependence and current and electro-optic response The investigations on the electro-optic response apparent tilt angle and spontaneous polarisation were performed using sandwich cells of 2 pm thickness inserted in a special holder allowing application of a unidirectional mechanical shear to the cells..Thus the liquid crystal layer was aligned in a bookshelf geometry with smectic layers perpendicular to the Fig. 2 Miscibility diagram for various compositions of (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl 5-(4-decyloxyphenyl)thiophene-2-carboxylate 2 with the standard (R)-(-)-1-methylheptyl 4-(4-decyloxybenzoyloxy)biphenyl-4-carboxylate 14 glass substrates. During the measurements the texture of the layer was kept uniform. The field-induced transition either from the ferri-or anti-ferro-electric phase to the ferroelectric phase can also be characterised by an increase in the birefringence of the sample which is linked to changes in the sample colour. Plates 5-8 show clearly the textural changes indicative of the field-induced transition of the antiferroelectric phase to the ferroelectric phase at varying applied voltages.Domains along the smectic layers were formed during this transition. The apparent tilt angle Oapp was measured under a low frequency square voltage (quasi dc conditions) by suitable movement of the turntable of a polarizing microscope i.e. the smectic C cone angle or twice the tilt angle was determined by detecting the position of the two minima in the transmitted light through the sample as it was rotated between crossed polarisers.. The spontaneous polarisation Ps was measured according to the capacitance bridge method.I5 The temperature dependence of the apparent tilt angle Oapp and spontaneous polarisation P is shown in Fig.3 and 4 Plate 5 Field-induced changes of a sample of 2 at 75 "C (antiferroelec-tric phase) where E=O V pm-' J. Mater. Chem. 1996 6(12) 1871-1878 1873 Plate 6 Field-induced changes of a sample of 2 at 75 "C (antiferroelec-tric phase) where E =7 V pm Plate 7 Field-induced changes of a sample of 2 at 75 "C (antiferroelec-tric phase) where E =7 5 V pm Plate 8 Field-induced changes of a sample of 2 at 75 "C (antiferroelec-tric phase) where E=9 V pm-I (ferroelectric state) respectively Fig 3 reveals that the material possesses a large Oapp in the field-induced Sc* phase. The temperature depen- dence of Ps at 60 "C(Fig 4),which has been measured at high enough voltages to be safely in the ferroelectric state during the temperature scan reveals a maximum value of approxi- mately 140 nCcm-' for the spontaneous polarisation In addition Oapp and Ps have rather large values at the Sc*-SA phase transition which coupled with the DSC measurements further suggests the first-order nature of this transition The voltage dependence of the spontaneous polarisation P at different temperatures is shown in Fig 5(u-c) In the Sc*(ferro) phase a very low field is required in order to unwind 1874 J Muter Chem 1996 6( 12) 1871-1878 c -I a? 26 ~~~11111 11~1 11 11 1 11 111 1111~1 ~~ 2055 60 65 70 75 80 85 90 95 TI'C Fig. 3 Temperature dependence of the apparent tilt angle Oapp for 2 at an applied electric field of E =32 V pm 14017--7120 1001 0 0 0 0 0 6o i Fig.4 Temperature dependence of the spontaneous polarisation P for 2 the helix and hence achieve saturation of the P [Fig 5(u)] Monitoring the voltage dependence of P at 79°C [Fig 5(b)] reveals clearly the presence of the ferrielectric phase 1 e at very low values of the applied electric field P increases steadily and then reaches a short-lived plateau (threshold voltage Vc= 9 V) Ps then increases rapidly and reaches a second stable saturation point whereby the sample is in the field-induced ferroelectric state Importantly the value of P at the threshold voltage is about 35 nC cmP2 which is approximately one third of the value corresponding to the P of the field-induced ferroelectric state which is in agreement with the suggested structure of the ferrielectric phase.The threshold behaviour of Ps in the ferrielectric phase is further illustrated in Fig 6 which depicts a characteristic current hysteresis loop at lower and higher voltages with respect to V Similarly Fig 5(c) shows the voltage dependence of P at 60°C (antiferroelectric phase) In this situation at low voltages the P is very small compared to the corresponding value (saturation) at high voltages which is attained following an extremely sharp thresh- old voltage. The rather small value for P at low voltages may be attributed to incomplete relaxation of the antiferroelectric phase . Monitoring of the current and electro-optic response charac- teristics of a liquid crystal material is a useful method which may be used to aid the process of phase assignment As depicted in Fig 7(u,b) compound 2 at 65 "C exhibits a double electro-optical hysteresis loop double current peak and electro- optical response with three states typical of the antiferroelectric state 1 e one field-off stable antiferroelectric state and two field-induced ferroelectric states Each of these peaks are associated with certain changes in the shape of the electro- optical response Fig 8(u-d) show the changes which take place in the current response trace on moving from the antiferro- to the ferro-electric phase via the ferrielectric state Fig.5 Voltage dependence of P at (a) 88°C [short pitch S,*(.ferroelectric) phase] (b) 79 "C (ferrielectric phase) and (c) 60 "C (antiferroelectric phase) Fig. 6 Current hysteresis loops at T=79 "Cfor two different strengths of the applied field less (E= 5 V pm-'),smaller hysteresis loop and higher (E= 13 V pm-') larger hysteresis loop Fig.7 (a)Electro-optical and current response for a 2 pm thick sample in the antiferroelectric phase.. The traces 1,2 and 3 are the applied voltage optic and current response respectively. (b) Electro-optical hysteresis loop for a 2 pm thick sample in the antiferroelectric phase The second current response peak observed in the antiferroelec- tric phase is no longer observed for the ferrielectric phase.. The remaining current response peak appears to be a combination of several peaks which is usually the case when the liquid crystal material is in the ferrielectric phase. Finally in the ferroelectric phase only one peak is present in the current response.Experimental Structural confirmation of the structures of the intermediates and the products was obtained by H NMR spectroscopy (JEOL FX60Q 270 MHz spectrometer) with tetramethylsilane as internal standard and infrared spectroscopy ( Perkin-Elmer FT 1605 spectrophotometer). Mass spectra were determined with an A.E.I. MS 902s spectrometer equipped with a Mass Spectrometry Services 200 console and an INCOS 2300 data system.. Thermal optical microscopy was carried out with a Vickers M75 polarising microscope in conjunction with a Mettler FP52 hot stage and FP5 control unit.. Thermodynamic data were recorded using a Perkin-Elmer DSC7 differential scanning calorimeter.4-Methoxyp henyl boronic acid 4 In an atmosphere of nitrogen commercial 4-bromoanisole 3 (107 g 0.57 mol) in dry tetrahydrofuran (100ml) was added Fig. 8 Electro-optical and current response for 2 pm thick sample of 2 at (a) T=55 C (antiferroelectric phase) (b) T=77 C (near the antiferroelectric-ferrielectric transition) (c) T= 79 8 "C (ferrielectric phase) and (d) T =90 C (ferroelectric phase) when a voltage of Up =65 V and f=2 Hz is applied to the cell dropwise to a stirred mixture of magnesium turnings (15 8 g 0 65 mol) a single crystal of iodine and dry tetrahydrofuran (50 ml) at such a rate that the tetrahydrofuran boiled gently After stirring for an additional 4 h the resultant solution of the Grignard reagent was transferred to a pressure equalising funnel and was then added dropwise to a vigorously stirred solution of trimethyl borate (1 15 mol 129 ml) in dry tetra- hydrofuran (100 ml) maintained at -78 "C.The ensuing white suspension was stirred for a further 1 h at -78 "C and then allowed to warm to room temperature overnight. The reaction mixture was then hydrolysed with 4 M aqueous hydrochloric acid and stirred for 1 h at room temperature and the product was extracted with diethyl ether (3 x 150 ml) dried (MgSO,) and the solvent removed zn uucuo to give an off-white solid The crude product was purified by recrystallisation from water to afford pure 4-methoxyphenylboronic acid 4 (43 65 g 50%) as a white solid mp 201-203 "C 6,(CDCl,-[2H,]DMSO) 4 9 (3H s CH,O) 68-82 (4H m ArH) [B(OH) protons not detected] ~~~~(KBr)/cm-~ 3465 (0-H str) 2966 1604 1374 1340 1247 1171 1111 1020 747 2-(4-Methoxyphenyl) thiophene 5 In a nitrogen atmosphere a solution of 4-methoxyphenyl-boronic acid 4 (5 5 g 0 084 mol) in ethanol (30 ml) was added to a vigorously stirred mixture of 2-bromothiophene (5 1 g 0 031 mol) tetrakis( triphenylphosphine)palladium(O) (0 3 mol%) 2 M aqueous sodium carbonate (30 ml) and ben- zene (30 ml). The reaction mixture was heated under reflux for 16 h cooled extracted into diethyl ether (3 x 100 ml) dried (MgSO,) and the solvent evaporated to yield a brown oil Purification was achieved by column chromatography on silica gel eluting with 3 1 light petroleum (bp 40-60 "C)-chloroform followed by recrystallisation from ethanol to afford the desired 2-( 4-methoxyphenyl) thiophene 5 (54 g 55%) as a white solid mp 107-108 "C (lit ,I7 105-106"C) GH(CDC1,) 3 8 (3H s CH,O) 72 (7H m ArH) vrn,,(KBr)/cm-l 3446 3098 2960 2834 1605 1500 1292 1261 1246 1184 1031 810 705 2-( 4Hydroxyphenyl) thiophene 6 In an inert atmosphere of nitrogen boron tribromide (2 10 ml 0 023 mol) was added dropwise to a stirred solution of 2-(4-methoxypheny1)thiophene 5 (4 9 g 0 015 mol) in dry dichloro- methane (17 ml) at such a rate ensuring that the reaction temperature remained at -78 "C.The reaction mixture was then allowed to warm to room temperature overnight recooled to -78"C and the excess of boron tribromide was then destroyed by the addition of methanol (5 ml).The mixture was acidified (4 M HCl) extracted with diethyl ether (3 x 50 ml) washed with water dried (MgS0,) and the solvent removed zn uacuo. The resulting green solid was purified by 1876 J Mater Chem 1996 6(12) 1871-1878 flash chromatography on silica gel eluting with 1 4 ethyl acetate-light petroleum (bp 40-60 "C),to yield the desired 2- (4-hydroxypheny1)thiophene6 (1 3 g 36%) mp 140-142 "C (lit ,I8 143-145 "C) hH(CDCl3) 7 1 (7H m ArH) 8 7 (lH br s OH disappears on D20 shake) vmax(KBr)/cm-' 3376 (0-H str) 1609 1501 1255 1173 817 688 2-( CDecyloxyphenyl )thiophene 7 Commercial 1-bromodecane (0 0017 mol) was added to a vigorously stirred mixture of 2-(4-hydroxyphenyl) thiophene 6 (040 g 0 0013 mol) anhydrous potassium carbonate (048 g 0 0034 mol) and dry acetone (20 ml).The reaction was heated under reflux for 24 h cooled filtered to remove any insoluble material and the filtrate evaporated to dryness. The crude product was recrystallised from ethanol to yield the desired 2- (4-decyloxyphenyl) thiophene 7 (0 36 g 88%) mp 74-75 "C as a white solid d,(CDCl,) 0 9 (3H t CH,) 12-1 4 (14H m alkyl) 1 8 (2H quintet CH2CH20) 3 9 (2H t CH20) 6 6-7 6 (7H m ArH) v,,,(KBr)/cm ' 2930 2860 1620 1530 1500 1470 1290 1250 1040 850 700 5-(4-Decyloxyphenyl ) thiophene-2-carboxylic acid 8 In an inert atmosphere of nitrogen 1 6 M butyllithium (2 1 ml 0 0032 mol) was added to a stirred solution of tetramethyl- diaminomethane (TMEDA) (034 g 0 003 mol) in dry hexane (50 ml).The resulting mixture was stirred at room temperature for 30 min after which 2-( 4-decyloxyphenyl) thiophene 7 (0 003 mol) in dry hexane (50 ml) was added dropwise and the reaction mixture was heated under reflux for 4 h. The reaction mixture was then cooled poured onto a large excess of solid carbon dioxide and allowed to stand overnight. The resulting slurry was acidified (4 M HCl) extracted with diethyl ether dried (MgSO,) and the solvent removed zn uucuo to yield the crude carboxylic acid 8 which was used for the next step without further purification Benzyl4-benzyloxybenzoate 10 Compound 10 was prepared from benzyl bromide (495g 0 29 mol) commercial 4-hydroxybenzoic acid (20 0 g 0 15 mol) anhydrous potassium carbonate (55 7 g 0 40 mol) and dry acetone (200ml) using the method described pre- viously for the synthesis of 24 4-decyloxyphenyl) thiophene 7 (71%) mp 127-128 "C dH(CDC1,) 5 0-5 3 (4H d 2 x CH20) 69-80 (14H m ArH) v,,,(KBr)/cm-l 3455 2951 2876 1698 1604 1509 1272 1169 1002 857 QBenzyloxybenzoic acid 11 Benzyl 4-benzyloxybenzoate 10 (24 0 g 0 075 mol) potassium hydroxide (38 g 0 68 mol) and 80% aqueous ethanol (300 ml) were heated under reflux for 4 h.The resulting white solid was filtered off acidified (4~ HCl) extracted with diethyl ether (3 x 50 ml) dried (MgSO,) and the solvent was removed zn ljucuu to give a white solid Purification was achieved by crystallisation from ethanol to afford the desired 4-benzyl- oxybenzoic acid 11 (99"/0) mp 188-190°C as a white solid dH(CDC13-[2H,]DMSO) 5 2 (2H s CH20) 7 0-8 0 (9H m ArH) 12 3 (lH br s OH disappears on D20shake) v,,,(KBr) 3463-2867 (0-H str) 1686 (C=O str) 1606 1512 1453 1304 1258 1169 1014 848 782 695.(R)-(-)-1-Me th ylhept y 1 4-benz ylox ybenzoa te 12 4-Benzyloxybenzoic acid 11 (6 0 g 0 026 mol) (R)-(-)-octan- 2-01 (3 4 g 0 026 mol) and 4-dimethylaminopyridine (DMAP) (10 mol%) were dissolved in dry dichloromethane (180 ml) stirred for 5 min at 0 "C and 1,3-dicyclohexylcarbodi1mide (5 4 g 0 026 mol) was then added. The reaction was then stirred for 6 h at room temperature the white insoluble solid produced during this period was filtered off and discarded and the filtrate evaporated to dryness. The crude residue was purified by column chromatography on silica gel eluting with 9 1 chloroform-light petroleum (bp 40-60 "C).The desired fractions were collected and the solvent removed in uucuo to give the desired (R)-(-)-1-methylheptyloxy 4-benzyloxybenzo- ate 12 (%YO) as a clear oil GH(CDCl,) 09 (3H t CH,) 1 2-1 4 (13H m CHCH3 and alkyl) 5 2 (3H m CH20 and CHCH,) 7 5 (9H m ArH) v,,,(thin film)/cm-' 2958 2857 1711 (C=O str) 1605 1276 1250 1102 846 (R)-(-)-4-( 1-Methylheptyloxycarbonyl)phenol 13 (R)-(-)-1-Methylheptyl 4-benzyloxybenzoate 12 (2 5 g 0 007 mol) was added to a stirred suspension of 10% Pd-C in ethanol (100 ml) and hydrogenated at room temperature and atmospheric pressure.After uptake of the appropriate amount of hydrogen (ca 24 h) the catalyst was filtered off and the filtrate was evaporated to dryness to afford the desired (R)-(-)-4-( 1-methylheptyloxycarbony1)phenol13 (89Y0) as a clear oil d,(CDCl,) 1 3 (16H m alkyl) 5 2 (1H m CHCH,) 7 6 (5H m ArH) v,,,(thin film)/cm-' 3356 (0-H str) 2930,2858 1710 (C=O str) 1605 1281 1165 1113 851 (I?)-( -)-4-(1-Methylheptyloxycarbonyl)phenyl5-(4decyloxyphenyl) thiophene-2-carboxylate 2 5-( 4-Decyloxyphenyl )thiophene-2-carboxylic acid 8 (0 00069 rnol) (R)-(-)-4-( I-methylheptyloxycarbony1)phenol13 (0 11 g 0 00069 mol) and 4-dimethylaminopyridine (DMAP) (10 mol%) were dissolved in dry dichloromethane (25 ml) stirred for 5 min at 0 "C and 1,3-dicyclohexylcarbodiimide (0 14 g 0 00069 mol) was then added Treatment as for com- pound 12 gave a crude residue which was purified by column chromatography on silica gel eluting with 3 1 chloroform- light petroleum (bp 40-60 "C) followed by several recrystalli- sations from ethanol to give the desired (R)-(-)-44 1 -methyl- heptyloxycarbony1)phenyl 5-(4-decyloxyphenyl)thiophene-2-carboxylate 2 (0 35 g 86%).The melting point and transition temperatures for compound 2 are listed in Table 1 (Found C 73 01 H 8 15 C36H4805S requires C 72 97 H 8 1lY0) dH(CDC1,) 0 9 (6H t 2 x CH,) 1 2-1 4 (27H m alkyl) 1 75 (2H m CH2CH20) 40 (2H t CH,O) 5 1 (lH m CHCH,) 69-76 (4H dd ArH) 7 15 (4H m ArH) 72 and 785 (2H dd ArH) vmax(KBr)/cm-' 2961 2923 1720 (C=O) 1605 1448 1261 1197 1078 1021 803 Conclusion.From our microscopic thermal and electro-optical investi- gations we can conclude that (R)-(-)-4-( l-methylheptyloxycar- bony1)phenyl 5-( 4-decyloxyphenyl) thiophene-2-carboxylate 2 exhibits the S,*ferro- fern- and antiferro-electric phase types . This is the first known example of a thiophene-based material which exhibits these phase types It is envisaged that other homologues derived from 5-( 4-alkoxyphenyl) thiophene-2- carboxylic acid 9 and (R)-(-)-4-( 1-methylheptyloxycarbony1)-phenol 13 are likely to exhibit similar phase types To this effect we are currently synthesising members of an homologous series of (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl 5-( 4- decyloxyphenyl)thiophene-2-carboxylates together with more elaborate physical-electro-optical studies.The results of this work will be published in a later communication . References . 1 A Fukuda Y Takanishi T Isokaki K Ishikawa and H Takezoe J Mater Chem ,1994,4997 2 J W Goodby A J Slaney C J Booth I Nishiyama J D Vuijk P Styring and K J Toyne Mol Cryst Liq Cryst 1994,243,231 3 S-L Wu D-G Chen S-J Chen C-Y Wang and J-T Shy Mol Cryst Liq Cryst 1995,264,39 J Mater Chern 1996,6(12) 1871-1878 1877 . 4 5 6 A D L Chandani E Gorecka Y Ouchi H Takezoe and A Fukuda Jpn J Appl Phys ,1989,28 L1265 R Brettle D A Dunmur C M Marson and K Toriyama Lzq Cryst 1993,13,515 A J Seed K J Toyne and J W Goodby J Muter Chem 1995 11 12 13 14 15 E Chin and J W Goodby Mol Cryst Liq Cryst 1986 141,311 A Hassner and V Alexanian Tetrahedron Lett 1978,4475 J Goodby J Muter Chem 1991,1,307 J Goodby J S Pate1 and E Chin J Muter Chem ,1992,2 197 G Andersson PhD. Thesis 1992 Chalmers University of 7 8 5,653 J L Butcher D J Byron A S Matharu and R C Wilson Lzq Cryst 1995,19,387 N Miyaura T Yanagi and A Suzuki Synth Commun 1981 11 16 17 Technology Sweden H Takezoe J Lee Y Ouchi and A Fukuda Mol Cryst Liq Cryst 1991,202,85 L J Baldwin S Pakray and R N Castle J Heterocycl Chem. 513 1985,22,1667 . 9 J F McOmie M L Watts and D E West Tetrahedron 1968 18 F Fringuelli G Marino and A Taticchi J Cheni Soc B 1970 24,2289 1595 10 V Faye J C Rouillon C Destrade and H T Nguyen Lzq Cryst 1995,19,47 Paper 6/01677D Received 11th March 1996 1878 J. Muter Chem. 1996 6(12) 1871-1878

ISSN:0959-9428    

DOI:10.1039/JM9960601871

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Preparation and characterization of Au-dispersed Ti02 thin films by a liquid-phase deposition method Shigehito Deki,* Yoshifumi Aoi, Hiroshi Yanagimoto, Katsuyuki Ishii, Kensuke Akamatsu, Minoru Mizuhata and Akihiko Kajinami Department of Chemical Science & Engineering, Faculty of Engineering, Kobe University, Rokkodai-cho, Nada-ku, Kobe 657, Japan Au-dispersed Ti02 (anatase) thin films have been prepared by a novel method, liquid-phase deposition (LPD) The deposited film\ were characterized by XRD, XPS, TEM and UV-VIS absorption spectroscopy The results showed that the titanium oxide thin film containing Au"' ions was formed from a mixed solution of ammonium hexafluorotitanate, boric acid and tetrachloroauric acid Heat treatment above 200 "C of the deposited film under flowing air produced dispersed Au metal particles, accompanied by the crystallization of titanium oxide as a matrix The mean particle size of the dispersed Au particles was ca 15 nm The optical absorption band due to the surface plasmon resonance of the dispersed Au particles shifted toward longer wavelengths with increasing heat- treatment temperature Microcrystals of metals and semiconductor-doped glasses have been studied in detail due to their large optical non-linearity These glasses are expected to be used in optical logic devices in an optical information context Generally, these metal- dispersed glass films or thin layers are prepared by r f sputter-ing,' ion-implantation2 and the sol-gel method For dry processes such as r f sputtering and ion-implantation, special apparatus and high energies are required for the preparation of films In addition, they are not suitable for the preparation of films on substrates with large surface areas, because they need vacuum or low pressure in operation For the sol-gel method, it is difficult to prepare thin films on substrates with complex surface morphologies Recently, we have developed a very simple wet process for the preparation of TiO2 thin films, the liquid-phase deposition (LPD) method In this process, transparent anatase thin films form directly on the substrate immersed in a mixed solution of ammonium hexafluorotitanate [( NH,),TiF,] and boric acid ( H3B03) In solution, the following ligand-exchange (hydroly- sis) equilibrium reaction of (NH,),TiF, is presumed TiFG2 +nH20+TiF6-n(OH)n2-+rzHF (1) This equilibrium reaction is shifted to the right-hand side by the addition of boric acid which reacts readily with F-and forms stable complex ion as follows H3B03+4HF BF,-+H30++2H20 (2) The addition of H3BO3 leads to the consumption of non-coordinated F-ions and accelerates the ligand-exchange (hydrolysis) reaction ( 1) Consequently, titanium oxide thin films form on the substrate immersed in the solution6 This process can be applied readily to the preparation of thin films on substrates which have complex morphologies and large surface areas without special equipment, because the LPD process is performed in an aqueous solution system Multi-component oxide thin films can be formed by the addition of the objective metal ion to the treatment solution In this study, we tried to prepare an Au-dispersed T10, thin film using the LPD method by adding tetrachloroauric acid (HAuC1,) solu-tion to the solution of (NH,),TiF, and H3B03 The films deposited were characterized by XRD, XPS, TEM and optical absorption spectroscopy Experimental As parent solutions, (NH,),TiF, (Kishida Chemical Co Ltd ) and H3B03 (Nacalai Tesque Inc) were dissolved in distilled water at concentrations of 0 5 mol dmP3, and HAuC1, (Wako Pure Chemical Industries Ltd ) was dissolved in distilled water at a concentration of 24mmol dm-3 These solutions were mixed at various compositions and used as the treatment solution for deposition The films were formed at a concen- tration of 0 1 mol dm-3 for (NH,),TiF, and of 0 2 mol dm-3 for H3BO3 This solution composition is that corresponding to the concentration at which the transparent anatase thin film was formed6 The concentration of HAuC1, in the treat- ment solution was varied from 0 1 to 10 mmol dm Most of the experiments were performed with the concentration of HAuCI, at 0 29 mmol dmP3 Non-alkali glass (Corning, #7059) was used as the substrate After being degreased and washed ultrasonically, the substrate was immersed in the treatment solution and suspended therein vertically for 20 h The sub- strate was then removed from the solution, washed with distilled water and dried at ambient temperature Heat treat- ment was carried out in an air flow for 1 h at various temperatures from 100 to 600°C The atomic ratios of Au/Ti in the deposited films were determined by inductively coupled plasma atomic emission spectroscopic analysis (ICP-AES, Seiko Instruments Inc , SRS 1500VR) of the solutions produced by dissolving the films with dilute hydrochloric acid XPS analyses of the deposited films were carried out on a Shimadzu ESCA 750 instrument XRD studies of the deposited films were measured on a Rigaku RINT 2100 diffractometer with thin film attachment, using Cu-Ka radiation (40 kV, 40 mA, scanning step 0 Oln) Crystallite sizes of the dispersed gold were calculated using Scherrer's equation, L=O 94/2/8 cos 8, where L is the mean dimension of the crystallites, is the full width in radians subtended by the half maximum intensity width of the diffrac- tion peak, 0 is the diffraction Fngle and n is the wavelength of the Cu-KN radiation (154 A) In order to calculate the crystallite size, the intensities were accumulated by repeating the measurement 10 times Optical absorption spectra were measured with a UVIDEC 660 (Japan Spectroscopic Co Ltd ) Particle sizes of the dispersed Au metal were measured directly on a Hitachi H-7100TE transmission electron microscope Results and Discussion The deposited film was colourless, transparent and showed strong adherence to the substrate The film changed from colourless to purple on heat treatment J Muter Chem, 1996, 6(12), 1879-1882 1879 o 0.2 0.4 0.6 0.6 I [HAuCl,]/mmol dm3 Fig.1 Relationship between the Au/Ti atomic ratio of the deposited film and the concentration of HAuCl, in the treatment solution. Concentration of (NH,),TiF,: 0.1 rnol dmP3 and of H3BO3: 0.2 mol dmP3. Reaction time: 20 h. Fig. 1 shows the relationship between the concentration of HAuCl, in the treatment solution and the Au/Ti atomic ratio of the deposited films. The Au content of the deposited film increased up to cu. 0.16 with an increasing HAuCI, concen- tration in the treatment solution. This indicates that the Au content of the film is controllable over a wide range by controlling the concentration of HAuCl, in the treatment solution. In the XP spectra of the deposited films, the binding energy of Au 4f7,, was 86.3 eV for the as-deposited film, and was 84.3 eV for the film heat-treated at 600°C.The binding energy of Au 4f,,, for the as-deposited film was close to that of Au"' and that for the heat-treated film was assigned to Au metal.* Based on these data, gold exists as Au"' ionic species in the as-deposited film and these species decompose and become Au metal upon the heat treatment. The change of the colour of the film from transparent to purple indicates the formation of Au metal particles in the film caused by the heat treatment. The XRD patterns of the deposited films which were heat- treated at various temperatures for 1 h are shown in Fig. 2. The measurements were made at an X-ray incidence angle of 1".The as-deposited film and the film heat-treated at 100°C were amorphous without any significant diffraction peak. The diffraction peaks assigned to Au metal were observed for the deposited films after heat-treatment above 200 "C. The decomposition of Au"' ionic species with formation of Au I 0 1 10 20 30 40 50 28/degrees Fig. 2 X-Ray diffraction patterns of the deposited films heat-treated at various temperatures for 1 h. a, As-deposited film; b-g, films heat- treated at 100, 200, 300, 400, 500 and 600°C, respectively. 0,Au; 0, TiO, (anatase). Concentration of (NH4),TiF,: 0.1 mol dmP3; of H3BO3: 0.2 mol dm-3 and of HAuCl,: 0.29 mmol dm-3. Reaction time: 20 h. 1880 J. Muter. Chern., 1996, 6(12), 1879-1882 microcrystals occurred in the temperature range 100-200 "C.The full-width at half-maximum of the diffraction peaks of Au( 1 11) decreased as the heat-treatment temperature increased, indicating that the Au metal crystals aggregated and grew in crystallite size during the heat treatment. The crystallite sizes calculated using the Scherrer equation7 for the diffraction line from Au( 111) are summarized in Table 1. For the films heat-treated above 400 "C, diffraction peaks assigned to anatase as the matrix phase of the film were also observed. This indicates that the oxide phase as the matrix was transformed from amorphous to crystalline anatase by the heat-treatment simultaneously with the formation and aggregation of the Au metal particles. A TEM photograph of the deposited film after heat treat- ment at 400°C is shown in Fig.3. In order to study them with the TEM, gold-dispersed thin films were removed from the substrates by exposure to hydrogen fluoride (HF) vapour. The Au metal particles are spherical and uniformly dispersed in the film. Particle-size distributions of the dispersed Au metal for the films heat-treated at 400, 500 and 600°C are shown in Fig. 4. 300 Particles were counted to obtain the distributions shown. The size distributions became broad as the heat- treatment temperature increased. The mean particle sizes of dispersed Au metal are summarized in Table 1. The optical absorption spectra of the deposited films after heat-treatment for 1 h are shown in Fig. 5. The absorption spectrum of the as-deposited film showed no absorption bands except for that below 400 nm due to the interband transition of the TiO, matrix.The absorption bands due to the surface plasmon resonance of the Au metal fine particles were observed for the deposited films heat-treated above 200 "C. The plasmon band increased in intensity and shifted toward longer wave- lengths from 555 to 608 nm, with increasing heat-treatment temperature. The change of the absorption peak position of the deposited films heat-treated at various temperatures is Table 1 Crystallite and mean particle sizes of the dispersed Au metal particles in the films heat-treated at various temperatures heat-treatment crystallite mean temperature/"C size/nm particle size/nm 200 8.5 300 11.5 - 400 12.4 14.6 500 14.0 17.4 600 14.0 15.6 Fig. 3 TEM photograph of the deposited film heat-treated at 400 "C for 1 h. Concentration of (NH,),TiF,: 0.1 mol dm-3; of H3B03: 0.2 mol dm-3 and of HAuC1,: 0.29 mmol dmP3.Reaction time: 20 h. t 620I30 0 10 20 30 40 2\ 20 c a,;10-L 0 0 10 20 30 40 30t I 0 10 20 30 40 diameterhm Fig. 4 Size distributions of dispersed Au metal particles in the deposited films heat-treated at 400 (a), 500 (b) and 600°C (c). Concentration of (NH,),TiF,: 0.1 mol drn-,; of H3B03: 0.2 mol dm-3 and of HAuC1,: 0.29 mmol dm-3. Reaction time: 20 h. ----a I 400 500 600 700 800 wavelengthhm Fig. 5 Optical absorption spectra of the deposited films heat-treated at various temperatures for 1 h.a, As-deposited film, b-g, films heat- treated at 100, 200, 300, 400, 500 and 600 "C, respectively. Concentration of (NH,),TiF,: 0.1 mol dm-3; of H3B03:0.2 rnol dm-3 and of HAuCl,: 0.29 mmol drn-,. Reaction time: 20 h. shown in Fig. 6. The peak wavelength shifted slightly to longer wavelengths up to 300 "C, then shifted markedly with increas- ing heat- trea tmen t temperature. For other gold-dispersed glasses, similar red shifts have been rep~rted.'.~'~ The plasmon band is affected by the dispersed metal particle size, the relative permittivity of the surrounding matrix and the aggregation of the metal particles.'-13 For colloidal gold particles in water, Bloemer et reported that the peak wavelength of the surface plasmon resonance shifted ca.12.5nm toward longer wavelengths with increasing particle size from 5 to 30 nm. In our samples, the peak wavelength shifted by ca. 55 nm towards longer wavelengths with increasing heat-treatment tempera- ture, although the mean particle sizes of the dispersed gold are almost constant around 15 nm for the films heat-treated above 400°C (Table 1). The absorption coefficient, ct, of the plasmon 6oo' 1 s0c 580' 3 Y3 560' a c ~nL2-L-uJ4U0 100 200 300 400 500 600 heat-treatment temperature/"C Fig. 6 Relationship between the peak wavelength of the surface plas- mon band of dispersed Au metal particles in the film and the heat- treatment temperature of the film.Concentration of (NH,),TiF6: 0.1 mol dm-3; of H,BO,: 0.2 rnol dmP3 and of HAuCI,: 0.29 mmol dmP3. Reaction time: 20 h. band of gold-dispersed glass is expressed as follows:2 w cc=p -lfJ2Ern/' (3)nc (4) Where &,(a) =E,' +i~," is the relative permittivity of the gold particles, &d is the relative permittivity of the matrix, p is the volume fraction of gold particles, co is the wavelength, n is the refractive index of the matrix, c is the velocity of light andf, is the local field factor. The maximum absorption is given by The peak wavelength of the plasmon resonance depends on the relative permittivity of the dispersed gold particles, which depends on the particle size,, and that of the matrix. As shown in Fig. 6, the peak wavelength shifted markedly towards longer wavelengths for the films heat-treated above 300°C.From the XRD patterns of the films (Fig. 2), the TiO, as matrix phase was transformed from amorphous to crystalline by heat-treatment above 300°C. Based on these results, we conclude that the shift of the plasmon band toward longer wavelengths by the heat-treatment was caused by the change in relative permittivity of the matrix due to the crystallization of TiO,. Conclusion We have developed a very simple process for the preparation of Au-dispersed TiO, thin films. The TiO, thin film containing Au"' ions was formed by the LPD method from a mixed solution of (NH,),TiF,, H3B03 and HAuC1, at ambient temperature and atmosphere. The LPD method is milder and more cost-effective than the conventional methods such as r.f.sputtering or ion-implantation, because it does not require special equipment. The Au content in the film was controlled easily by controlling the concentration of HAuCl, in the treatment solution. Heat-treatment of the deposited film above 200 "C produced Au metal particles which were ca. 15 nm in diameter. The size distribution of the dispersed Au particles became broad as the heat-treatment temperature increased. Crystallization of TiO, as the matrix occurred simultaneously with formation of Au metal particles during the heat treatment. Surface plasmon resonance bands were observed for the films heat-treated above 200°C. The peak wavelength shifted by ca. 55 nm towards longer wavelengths following the heat treat- ment.The shift of the peak position is caused by the change of the relative permittivity of the TiO, as the matrix crystallized. J. Muter. Chem., 1996, 6(12), 1879-1882 1881 The authors wish to thank Dr Keisuke Oguro and Ms Yasuko Ehara of Hydrogen Energy Section of Osaka National Research Institute, AIST for XPS measurements 4 5 H Shinojima, J Yumoto and S Uesugi, Appl Phys Lett, 1992, 60,298 B L Justus, M E Seaver, J A Ruller and A J Campillo, Appl Phys Lett, 1990,57,1381 6 S Deki, Y Aoi, 0 Hiroi and A Kajinami, Chem Lett, 1996,433 7 B E Warren, in X-Raj Difractron, Dover Publications, New References 8 York, 1969, p 253 J J Pireaux, M Liehr, P A Thiry, J P Delrue and R Caudano, T Kineri, M Mori, K Kadono, T Sakaguchi, M Miya, H Wakabayashi and T Tsuchiya, J Ceram Soc Jpn, 1993, 101, 1340 9 10 Surf Scr ,1984,141,221 U Kreibig and L Ganzel, Surf Scr , 1985, 156,678 U Kreibig, J Phys Coll C, 1977, 2,97 K Fukumi, A Chayahara, K Kadono, T Sakaguchi, Y Horino, M Miya, K Fujii, J Hayakawa and M Satou, J Appl Phys , 1994, 75,3075 J Matsuoka, R Mizutani, S Kaneko, H Nasu, K Kamiya, 11 12 13 R H Doremus, J Chem Phys, 1964,40,2389 M J Bloemer, J W Haus and P R Ashley, J Opt Soc Am B, 1990,7,790 G W Arnold, J Appl Phys, 1975,46,4466 K Kadono, T Sakaguchi and M Miya, J Ceram Soc Jpn , 1993, 101,53 Paper 6/04806D, Received 9th July, 1996 1882 J Muter Chem, 1996, 6(12), 1879-1882

ISSN:0959-9428    

DOI:10.1039/JM9960601879

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Selectivity and compositional dependence of response of gas-sensitive resistors Part 4.t-Properties of some rutile solid solution compounds Geoff S. Henshaw Ljuibov Morris Laura J. Gellman and David E. Williams* Chemistry Department University College London 20 Gordon St London UK WClH OAJ Solid solutions based on the rutile structure offer the possibility of independently varying the cation composition and dopant density in the lattice and hence exploring the effects that these have upon the electrical response to reactive gases. Thus solid solutions of CrNbO (p-type response) with Nb-doped T10 and FeNb0 (n-type response) have been investigated. The resistivities and activation energies increased in the order FeNbO <CrNbO <Ti 975Nb0 02502 which is explained in terms of the emptying and decreasing energy of the eg and tZg states within the bandgap.The n-p transitions can similarly be discussed in terms of the localised occupancy of these levels and the energy of the reactive oxygen surface state with respect to them Sensitivity to CO decreased in the order Ti 975Nb0 02502 >CrNbO FeNb0 and this was postulated to be due either to Nb5 + surface segregation or to the narrowing of the conduction bandwidth leading to valence trapping of electrons An enhanced gas response at T <300 "C was found for the compounds after they had been heated to cu 700 "C in air. This was attributed to the desorption of surface hydroxy carbonyl and lattice oxygen species to produce a vacancy around which the surface reconstructed It is proposed that ionosorption of oxygen at this site produced a species able to react with CO and produce a resistance change at low temperatures The study of the electrical properties of metal oxide solid- solution compounds provides information on the effects of systematic cation substitution relevant to gas-sensor appli- cations Although response models for semiconducting oxide gas sensors exist the level of understanding required to predict the gas-sensing behaviour of an oxide from its electrical and structural properties has not been reached Instead an empiri- cal approach is usually taken to determine which properties might be important The usual model for the response is in terms of a reaction of an adsorbed oxygen species with the gas' and the expectation is first that this should in some way depend upon the nature of the sites and the species present at the surface and secondly that useful differences in behaviour should arise from manipu- lation of this chemistry A very broad description can be given2 which shows that the general patterns of behaviour in which oxides and gases may be classified as n-or p-type oxidising or reducing respectively according to the sign of the response can be interpreted in terms of this adsorbed oxygen species acting as a surface trap for electrons with the sign of the response governed by the bulk donor density Separation of the two effects of dopant density and surface sites would seem necessary in order to advance understanding of the surface chemistry behind the gas response.Systematic cation substitution in solid-solution compounds as a route to understanding the surface chemistry mediating gas response has previously been studied in Cr -,Ti,02 +x 34 Ba,Fe,Nb ,0305and (CrNb0,),(Sn02) -x,6 and the effects of surface segregation stoichiometry microstructure and com- bustion gradients on gas response have been explored CrNbO and FeNbO both exhibit rutile structures and solid-solution compounds spanning FeNbO,-CrNbO,-TiO can easily be made In this series therefore the possibility exists of independently varying the cation composition of the lattice and the dopant density (by substitution of Nb5+ for Ti4+)so that the effects of each of these might be explored Furthermore CrNbO shows a p-type gas response (resistance decrease in the presence of reducing gases') while both T10 t Part 3 ref 6 and FeNbO are n-type therefore n-p transitions are expected at some mole fraction.In this study the effects of changing the cation composition by the incorporation of CrNbO on the electrical properties and sensing behaviour to carbon monoxide of the solid-solution series (CrNbO,),( FeNb04)1 -x and (CrNbO,) (Ti -yNby02)1 -,(y =0 0 01,O 025 0 05) have been explored Experimental The compounds were synthesized by ball-milling stoichiometric quantities of Cr203 Nb205 Fe203 and T10 (Fluka >99% pure) in acetone for 12 h evaporating the solvent and then firing the powders at 1000°C for 12 h Powder X-ray diffractometry indicated that the materials except for FeNb0,- rich compositions (see below) were single phase with rutile structures The compounds were pressed into 13 mm diameter pellets at a pressure of 1000 kg cmP2 and fired at 1000"C.The pellet morphologies were characterised by scanning electron microscopy using a Hitachi s-570 SEM equipped with a LINK energy dispersive X-ray analyser. The pellet test rig has been described elsewhere. The resistances of the pellets were meas- ured every 60 s using a Keithley model 199 scanning digital multimeter. The furnace resistance measurements and gas- flow controllers were computer controlled. The sensitivity (Sgas) was defined as Sgas=Aa/o =(Rgas-Ralr)/RaIr,where cs denotes the conductivity (a in pure air) R, the resistance in air and Rgas the resistance in the gas Experiments which measured the pellet resistance as a function of temperature were per- formed with a temperature ramp rate of 1 "C rnin-'.The gas composition was switched from dry air to 1000ppm carbon monoxide for 20 min every 40 min X-Ray photoelectron spectra of pellets fractured ex sztu just before insertion were recorded on a VG ESCALAB 2201 XL using focused (300 pm spot size) monochromated Al-Ksl radi- ation at 20eV pass energy Scans were acquired with a step size of 100meV A 4eV flood gun was used to control the sample charging and the binding energies were referenced to the 'adventitious' C 1s peak at 284 8 eV Spectrum quantifi- cation was performed using a straight line background and sensitivity factors obtained from Wagner.Results Materials characterisation The XRD patterns of the (CrNbO,),(Ti 975Nb0 0250J1 - materials showed that solid solutions with the rutile structure had been achieved for the complete range 0 <x <1.. The a and c lattice parameter values (Fig. 1) increased with increasing CrNbO mole Tatio presumably due to the larger ionic radius of Nb5+ (0.64 A) us. Ti4+ (0.61 A).' SEM analysis of the pellet grain morphology showed no differences between compositions. The (CrNbO,),( FeNbO,) -,series exhibited a transition from monoclinic (x <0.08) to tetragonal (x>0.08) phases. All the tetragonal materials with x>O.2 were single phase.. The lattice parameters decreased slightly with increasing chromium content (Fig.1). SEM analysis of the pellets showed that the grain size and degree of necking/sintering increased with chromium content (grain size typically 1-5 pm for FeNbO increasing to 5-10 pm for Cr ,Fe ,NbO,) which was consist- ent with previous work that demonstrated the addition of Cr203 promoted grain growth in some ceramic materials.'' Surface analysis (Fig. 2) showed that Nb was surface-enriched in the CrNb04-Tio 975NbO ,2502 series the segre- gation possibly driven by the larger Nb5+ ionic radius.. The Nb 3d, binding energy varied from 206.5 eV for Ti g75NbO 02502 to 207.2 eV for CrNbO which was indicative of Nb5+ (c$. Nb02 205.7 eV; Nb205 207.6 eV; KNbO 206.5 evil).K and Na were also detected at the surface as impurities from the Ti02 and Cr,O starting materials respect- ively.. The valence-band spectra for Ti g75NbO 02502 CrNbO and Fe ,Cr ,NbO are shown in Fig. 3.. The 3d band intensity Il,IIlII,-4 78 -3 08 476 -w,-' -3 06 474 -3 04 02 300 0 9a 96 4 64 -<-2 94 4 62 -2 92 1IIIIII1( 90 X Fig. 1 Plot of lattice parameters a and c us. composition for the solid solution compounds s-c I\ \ i ~. 0.0 0.2 0.4 0.6 0.8 lT0 CrNb04 mole ratio Fig. 2 Plot of surface cation concentration (atom%) us. CrNb0 mole ratio for the (CrNbO,),( Ti 97sNb002s02)1 Ti; A Nb; A,Cr; + K; 0,Na. -,compounds. Legend m \(C) 1 1412108 6 4 2 0 binding energy/eV Fig. 3 XPS valence band spectra of (a) Ti 9,sNb002s02,(b) CrNbO and (c) Fe *Cr 2Nb04 for the latter two compounds can be seen at a binding energy below that of the 0 2p band.The baseline resistances and the activation energies (E,) as a function of composition are shown in Fig. 4 and 5 respect-ively.. The resistivities increased in the solid-solution order FeNb0 <CrNbO <TiOz which is also the order of decreas-ing d-electron number.. The activation energies roughly fol- lowed the resistivity pattern. While the resistivity varied steadily with composition across the p-type range the acti- vation energy changed more sharply around the transition in n-type compounds. Gas response The sensitivity to 1000 ppm CO in air at 400 "C is shown as a function of solid-solution composition in Fig.6. Several points can be noted. First two n-p transitions occurred as expected. Secondly within each n-type or p-type conduction region a maximum sensitivity was observed.. Thirdly Nb-doped TiOZ exhibited the highest sensitivity within the composition range studied. 00 02 04 06 08 10 08 06 04 02 00 X Fig.4 Graph of resistivity at 340°C us. composition for the solid solution compounds FeNbO CrNbO 04Y02 I 111.1 I I I I I1 00 02 04 06 08 10 08 06 04 02 00 X Fig. 5 Graph of activation energy for conduction in the energy range 450-550 "C us. composition for the solid solution compounds 1884 J. Mater. Chem. 1996 6(12) 1883-1887 FeNbO CrNbO 975Nb0 025'2 10 4I n-type p-tw ul 00 02 04 06 08 10 08 06 04 02 00 X Fig.6 Graph of sensitivity (S=Aa/a,) to 1000 ppm CO at 400 "C us composition for the solid solution compounds. The dotted line rep- resents the postulated sensitivity in the absence of n-p transitions The sensitivity to 1000 ppm CO in air at 400°C of TI -,Nb,02 as function of Nb mole fraction is shown in Fig 7 The sensitivity decreased with increasing Nb doping. Typical behaviour during a temperature-ramp experiment with the gas atmosphere switched between air and 1OOOppm carbon monoxide is shown in Fig 8. The low-temperature (T<300 "C) resistance change induced by the presence of CO was markedly higher on the decreasing temperature side of 12 10 008 06 04 000 001 002 003 004 005 Nb mole ratio Fig. 7 Graph of the sensitivity to 1000ppm CO in air at 400"C of Ti ,Nb,O as a function of Nb mole fraction 7008 600 7 500 hc6 \U 400 fY m 9 5 300 4 200<-0 2 4 6 8 10 12 14 16 18 tlh Fig. 8 Resistance of (CrNbO,) 5(T~o us,,Nb 0102)o temperature for an experiment in which the gas is switched between dry air and 1000ppm CO while the temperature is ramped from 25 to 680 "C at 1"Cmin the ramp I e after exposure of the pellets to high temperature (T=700 "C) If after the high-temperature treatment the mate- rial was held at 25OoC the response to CO was retained in wet or dry air periods of up to 4 h were explored If after cooling to room temperature the pellets were exposed for some hours either to the laboratory atmosphere or to wet clean air the low-temperature response was lost and could only be recovered by heating again to high temperature Diffuse-reflectance FTIR studies showed that surface OH species present at 250 "C in the initial state were removed after heating to 700°C Discussion.Oxides with the rutile structure are simply particular packings of MO octahedra and one question concerns the extent to which d-states of the metal split by the octahedral crystal field are delocalised across the lattice Here the increase in conductivity across the series correlated with an increase in d- electron number do (Ti4+ Nb5+) d3 (Cr") d5 (Fe5+) so the electrical properties of the solid-solution series can be under- stood in terms of a progressive change in the filling and energies of localised non-bonding eg and t2g states of the metal with the conductivity controlled by excitation from these localised donor states into the conduction band.The increase in activation energies across the series indicated that the position of the highest occupied state within the bandgap dropped on going from FeNb0 through CrNbO to T10. The bandgap may also have changed across the series although this has not been measured. The conductivity in TiOz was a consequence of the population of Ti3+ donor states as a result of the Nb5+ doping. The expectation that in a series such as this the effects of surface composition and dopant density could be separated was too simplistic Altering the dopant density by changing the Nb concentration changed the surface composition as a consequence of surface segregation Changing the cation composition of the lattice changed the dopant density by changing the electron occupancy of non-bonding states localised on the metal .Early work' made predictions that around the transition from n- to p-type behaviour there should be changes in the sign of response with increasing gas concentration or improved specificity of response or a distinction between responses which were not mediated by adsorbed oxygen and those that were. These predictions were not tested in the present work but the formalism can be used to derive some further insight from the results From that and other work,'6 using the approximation of a surface-trap-limited conductance the key equilibria are those of surface acceptors (oxygen species) with the conduction and valence bands S-$S+n K1=N exp(-AE,/kT) S +S-+p' K =N exp [-(AE -AEJkT] with the resulting conductivity approximately given by Here N and N are the densities of states at the conduction and valence band edges respectively AE denotes the surface state energy with respect to the conduction band edge AEG the bandgap and N the total surface state density NA and ND denote the bulk concentrations of acceptor and donor states respectively which we identify as empty and filled metal d-orbitals as previously pr~posed,~ so (NA+N,) is constant The key to whether the behaviour is n- or p-type with respect to variation of Ns then lies in the relative values of K1 and K I e the position of the reactive surface oxygen states in the bandgap.The change in behaviour in the FeNb0,-CrNbO series is now clearly explicable if the surface oxygen state lies. between the e and t states with the emptying of the e state (high-spin Fe3+) the activation energy for conductance would increase by the crystal-field splitting and the response would change sign as the highest occupied local state shifted in energy from above to below the surface oxygen state (K1/K2would change from greater to less than unity). The change in sign in the CrNb0,-Ti 975Nb0 0z50,series can be explained by a shift in energy of the t level from below the oxygen surface state to above it as the surface Ti concentration increased. This is in agreement with density of states calculations for T10,I2 which places the t level at the conduction band edge and the XPS valence band spectra of CrNbO (Fig 3) which indicate the occupied 3d band liesjust above the 0 2p band at the valence band edge Fig 2 shows that the switch in gas- response behaviour occurred when the surface concentrations of Nb and Ti were approximately equal.The electrical response to CO exhibited a general decrease from T10 through CrNbO to FeNb0,. The response maxi- mum in the CrNbO p-type range can be interpreted as this general decrease superimposed upon the effect of the n-p transition as shown by the dotted line in Fig 6 One postulate is that this was due to the enhanced concentration of Nb5+ at the surface since from Fig 7 Nb doping reduced the sensitivity of T10,.This surface enrichment demonstrated that the gas response of these compounds was mediated at a surface with a quite different composition to the bulk It also suggested that the structure within the top few atomic layers of the surface was different to that of the bulk lattice since a charge compensation argument would require Cr3 + to accompany Nb5+ in a rutile structure No Nb4' was detected by XPS in the CrNbO,-TiO compounds FeNbO exhibited a low sensitivity to CO However the powder diffraction data indicated that this material was mono- clinic rather than tetragonal as found for compounds with CrNbO mole ratios above 008.The first pure tetragonal phase material (CrNbO,) ,( FeNbO,)o 8 exhibited the highest sensitivity of the compounds containing FeNbO,. Thus it appears that crystallographic phase changes can affect gas response and that in this case the monoclinic phase exhibited a poorer gas response than the tetragonal phase. The observed increase in grain size and intergrain necking with Cr203 content appeared to decrease the response to CO of the (CrNbO,),( FeNb04)1 -x compounds for x > 0 2. This sug-gested that the rate of reaction of CO was comparable to the diffusivity of the gas through the porous pellets l3 Nb-doped T10 exhibited the largest gas response had the highest resistivity and activation energy and uniquely in these compounds contained no 3d electrons A general observation that was stimulated by this result is that there appears to be a correlation between sensitivity to combustible gases and d- electron density since arguably the 'best' gas-sensing materials are either d10 (SnO ZnO) containing non-bonding d elec- trons or do (TiO W03) compounds.This might be related to differences in conduction bandwidth. The conduction band in post-transition-metal oxides such as ZnO and SnO is primarily composed of metal s orbitals which exhibit good overlap giving rise to quite large conduction bandwidths. This allows electron delocalisation and the formation of space charge layers in response to surface oxygen vacancies which are both prerequisites for good gas-sensor response In contrast the conduction band in transition-metal oxides has predomi- nantly d-orbital character which exhibits poor overlap and therefore narrow bandwidth (approximately 1 eV for the oxides of Fe to Cu compared with around 3eV for T10,14).The electrons released upon the loss of oxygen would be more likely to be localised ('valence-trapped') and not greatly alter the conductivity. Therefore the decrease in sensitivity exhibited by the solid-solution series could be attributed to a progressive narrowing of the conduction bandwidth due to its increasing d character T10 < CrNbO < FeNb0 1886 J Muter Chem 1996 6(12) 1883-1887 The augmented low-temperature response of these com-pounds to CO after heating to ca 700°C in air is in direct contrast to the response of SnO which is well known to exhibit a low-temperature response to CO which is dependent on the presence of surface OH groups l5 It is relatively easy to postulate that the increased low-temperature response was due to the desorption of unreactive surface species at 700°C followed by the adsorption of more reactive species such as ionosorbed oxygen which would then generate an electrical response to CO in the usual way Confirmation of this is more difficult Possible candidates for the species lost by high- temperature exposure include chemisorbed water (OH groups) surface carbonates and lattice 0'-Diffuse-reflectance FTIR spectroscopy indicated that the surface hydroxy group concen- tration at 250 *C was significantly diminished by prior heating to ca 700°C However the sensitivity to CO of a heated pellet was not reduced markedly by the presence of air at 100% relative humidity which would imply that the surface species was not water or that rehydroxylation at 250 "C was slow.The low-temperature response was removed by leaving the pellets exposed at room temperature to laboratory air for several days and was diminished by exposure for several hours at room temperature to clean wet air Hence the effect was unlikely to be caused by a change in the surface segregation of Nb on heating to 7OO0C since this would not revert at room temperature The desorption reactions can be written in Kroger-Vink notation in the following way for hydroxy groups 2[OH 1,' ~H20~+V,"+0," for bidentate carbonate [CO,' ],''-+CO,~+V,"+O," and for lattice oxygen (3) The oxygen vacancy (V * ' ) produced would cause the surface around it to restructure in particular the oxide lattice would pucker towards the vacancy It is postulated that this creates a site at which oxygen can ionosorb to produce the surface species involved in the reaction with CO at low temperatures Conclusions.The electrical properties and carbon monoxide sensing response of the solid-solution series of p-type CrNbO with Nb-doped T10 and FeNbO (both n-type) have been investi- gated. The resistivities and activation energies increased in the order FeNbO (d5) < CrNb0,(d3) < Nb-doped T10 (do) which was explained in terms of the progressive emptying and decreasing energy of the e and t states localised within the bandgap. The sensitivity to CO decreased in the order Nb- doped TiO,>CrNbO FeNbO and this was postulated to be due to both the detrimental effect of Nbs+ surface segre- gation and to a narrowing of the conduction bandwidth leading to valence trapping of electrons.The transitions between n- and p-type response could be interpreted in terms of a change in the energy of the oxygen surface state relative to the highest occupied metal d state either as a result of the emptying of the eg level in the (Fe,Cr)NbO series or as a result of a change in the t energy in the CrNb0,-Ti02 series as Ti replaced Cr at the surface An augmented gas response at T<300 "C was found for the compounds after they had been heated to ca 700°C in air This was attributed to the loss of surface hydroxy carbonyl and lattice oxygen species producing a vacancy around which the surface reconstructed to form an oxygen adsorption site with the oxygen species at this new site then able to react with carbon monoxide and produce a change in electrical resistance .We would like to thank EPSRC and Capteur Sensors and Analysers Ltd. for financial support of this work. 7 8 L. J. Gellman PhD. Thesis University College London 1995. C. D. Wagner L. E. Davis M. V. Zeller J. A. Taylor R. M. Raymond and L. H. Gale Surf. Interface Anal. 1981,3,211. 9 R. D. Shannon Acta Crystallogr. Sect. A 1974,32,751. References 10 C.I. Cheon S. J. Kim and H. G. Kim Ferroelectrics 19. 91,115 35. 11 C. D. Wagner in Practical Surface Analysis 2nd edn. vol 1 Auger D. E. Williams in Solid State Gas Sensors ed. P. T. Moseley and and X-ray Photoelectron Spectroscopy ed. D. Briggs and B. C. Tofield Adam-Higer Bristol 1987. D. E. Williams and P. T. Moseley J. Muter. Chem. 1991,1 809. 12 M. P. Seah John Wiley and Sons Chichester 1990. S. Munnix and M. Schmeits Phys. Rev. B 1984,30,2202. G. S. Henshaw D. H. Dawson and D. E. Williams J. Muter. Chem. 13 D. E. Williams G. S. Henshaw K. F. E. Pratt and R. Peat J. Chem. 1995 5 1791. Soc. Faraday Trans. 1995,91,4299. D. H. Dawson G. S. Henshaw and D. E. Williams Sensors 14 V. E. Henrich and P. A. Cox,. The Surface Science of Metal Oxides Actuators B 1995,26-27,76. G. S. Henshaw L. J. Gellman and D. E. Williams J. Muter. Chem. 15 Cambridge University Press Cambridge 1994. J. F. McAleer P. T. Moseley J. 0.W. Norris and D. E. Williams 1994 4 1427. G. S. Henshaw V. Dusastre and D. E. Williams J. Muter. Chem. J. Chem. Soc. Faraday Trans. 1987,83 1323. 1996,6 1351. Paper 6/04188D;Received 14th June 1996 J. Muter. Chern. 1996 6(12) 1883-1887 1887

ISSN:0959-9428    

DOI:10.1039/JM9960601883

出版商:RSC    

年代:1996

数据来源: RSC

摘要:

Structural relaxation and crystallization of semiconducting vanadate glass accompanying a jump of the electrical conductivity Tetsuaki Nishida,*" Junichi Kubota," Yonezo Maeda," Fusao Ichikawab and Takafumi Aomineb aDepartmentof Chemistry, Faculty of Science, Kyushu University, Hakozaki, Higashiku, Fukuoka 812, Japan bDepartment of Physics, Faculty of Science, Kyushu University, Hakozaki, Higashiku, Fukuoka 812, Japan * 10Fe203 glasses (20 <x d30) consists of a quadrupole doublet peak. The linewidth and the quadrupole splitting decreased gradually after heat treatment at the crystallization temperature, reflecting an increased uniformity of Fe- 0 bonds and a decreased distortion of FeO, tetrahedra, respectively. FTIR spectra of heat-treated vanadate glasses revealed an evident peak separation between VO, and FeO, tetrahedra. The FeO, units were not observed in non-treated glass because they occupy substitutional sites of VO,.An X-ray diffraction study of heat-treated glasses established the formation of a KV308 phase composed of VO, pyramids. Additional diffraction peaks due to a K3V5014 glasses plot of the differential thermal analysis (DTA) data yielded activation energies of 2.0-2.9 (d0.3) eV, indicating that cleavage of Fe-0 bonds with bond energies of ca. 2.6 eV triggers the crystallization. Magnetic susceptibility measurements of 25K20* 65V,05 * 10Fe203 glass revealed an antiferromagnetic behaviour with Curie-Weiss constants of -13, -93 and -108 K after the heat treatment at 340 "C for 0,2100 and 5000 min, respectively.A jump of the electrical conductivity from 6.3 x lo-' S cm-' to 4.3 x lo-, S cm-' and this can be ascribed to an increased probability of electron hopping from V4+ to V5+ which was brought about as a result of a decreased distortion of VO,, FeO, and V05 units. Electrical conducting glasses have attracted much interest in The Mossbauer effect is a very effective tool for investigating the field of solid-state chemistry and materials science because the local structures of inorganic glasses, in which small amounts they can be used as an electrode, solid-state electrolyte, sensor, of Mossbauer ions such as Fe3+ and Sn4+ are doped as a etc. Several vanadate (V,O,-based) glasses show a semiconduc- 'probe'. Information can be obtained from the Mossbauer ions tivity with the electrical conductivity (B) of the order of about on the chemical bond and the symmetry of the oxygen lo-' to Scrn-',' which is known to be due to the polyhedra of the network former (NWF), e.g., VO,, SiO,, electron hopping from V4+ to V5+ in the 'skeleton' structure. AlO,, GaO, and BO,, because the Mossbauer ions occupy The mechanism of semiconductivity was explained by Mott2 NWF sites in several oxide gla~ses."-'~ Nishida discovered and by Austin and Mott3 with a small polaron hopping theory, three general for determining the structural role of in which the activation energy, W, was estimated to be equal Mossbauer ions in inorganic glasses. (1) The Debye tempera- to the summation of the electron-hopping energy, W', and ture, OD, obtained from low-temperature Mossbauer measure- half of the lattice disorder energy, W,.In the case of ments, is >280K when iron and tin occupy NWF sites, Sb2O3-Sr0-V2O5 glasses,' W was reported to be 0.41-0.61 eV whereas it is <270 K when they occupy network modifier and W, <0.1 eV. (NWM) sites, as is usual for alkali-metal ions. (2) y-Ray The electrical conductivity of insulating oxide glasses is irradiation of oxide glass results in the reduction of Fe3+ to generally less than lo-'' S cm-l and the alkali-metal ions are Fe2+ when Fe3+ occupies NWF sites, while oxidation of Fe2+ known to be representative 'carriers'. Crystallization of oxide to Fe3+ takes place when iron occupies NWM sites. (3) The glass generally results in a decrease in the electrical conduc- glass-transition temperature, q,of oxide glasses has a linear tivity.By contrast, if a conducting crystalline phase like relationship with the quadrupole splitting, A, of Fe3+ obtained 'vanadium bronze', R,V205, precipitates in the matrix glass, from the Mossbauer measurements. The linear relationship, the electrical conductivities of glass ceramics will become named the 'G-d rule', gives a large slope of 680 "C (mm s-')-l higher than those of non-treated glass. In the case of potassium when Fe3+ occupies tetrahedral NWF sites, while the slope vanadate glass, 25K20-65V205 10Fe,03, an insulating becomes 260 "C (mm sF1)-l when Fe3+ occupies octahedral KV30E phase4 and a K3V5014 phase' are expected to precipi- NWF sites." By contrast, the slope becomes only tate upon heat treatment, and hence it is expected that the 35 "C (mms-')-' when Fe3+ occupies NWM sites.These electrical conductivity of the glass ceramic will decrease. findings made it possible to deduce the structural role of Vanadium pentoxide, V205, is known to have a layered Mossbauer ions in oxide and non-oxide glasses, i.e. whether structure composed of VO, pyramids.6 Structural studies of NWF or NWM. several glasses have been carried out by NMR,7 IRE and FTIR spectroscopy is also a powerful tool for studying the Mossba~er~'~~ Intechniques. As a result, the 'skeleton' proved to local structure and crystallization of inorganic glasse~.~~-~~ be composed of distorted VO, tetrahedra and distorted VO, -5Fe203 glass," tetragonal pyramids.It is generally considered that the fraction for example, precipitation of a mayenite (12Ca0. 7A1,03) of distorted VO, tetrahedra will increase with increasing alkali- phase was confirmed by a step-by-step peak shift of the A1-0 metal oxide content. A 57Fe Mossbauer study of alkali-metal stretching band (v3 mode) of distorted AlO, tetrahedra from vanadate glasses containing iron revealed that the fraction of 782 to 837 cm-l. The peak position is consistent with the non-bridging oxygen (NBO) in the distorted VO, tetrahedra characteristic IR frequency range elucidated by Tarte,20 i.e. increases with increasing alkali-metal oxide c~ntent.~"~ tetrahedral A13+ in a condensed material is observed in the J.Mater. Chem., 1996,6( 12), 1889-1896 1889 700-900 cm-l range, while octahedral A13+ bands are found in the region 500-650cm-'. In glass ceramics including the mayenite phase, phase separation of distorted FeO, tetrahedra, i.e. precipitation of an iron-rich phase in the glass phase, was elucidated from the new peak which appeared at 570cm-', which was assigned to the v3 mode of FeO, tetrahedra." Since the stretching band of octahedral Fe3+ in oxide glasses is generally observed at ca. 540 cm -,15,18,20 discrimination between tetrahedral and octahedral Fe3 + becomes possible from the IR measurements. Tarte2' elucidated that tetrahedral Fe3+ in a condensed material is observed at 550-700 cm-', while octahedral Fe3+ is found at 400-550 cm-l.An 'FTIR transmission method' combined with a conventional Johnson- Mehl-Avrami (JMA) equation is effective for the kinetic study of the crystallization of IR-transmitting gla~ses.'~.~~ In the present study, however, the FTIR transmission method has not been applied because vanadate glasses in general are not optically transparent in the IR region. Differential thermal analysis (DTA) is also effective for the kinetic study of the crystallization of glasses, and a Kissinger plot2' is often used for estimating the activation energy, E,. The Kissinger equation is expressed by In (x2/a)=E,/RT, +C (1) in which T, and a are the crystallization peak temperature (in K) and the heating rate of the sample, respectively; R is the gas constant and C is a constant.From the Kissinger plots of 38Na20 61 W03 * 57Fe203 and 38Na20 62W0, gla~ses,'~ E, values of 2.6 and 4.7 (k0.3) eV, respectively, were obtained. The former value can be assigned to the Fe-0 bond energy, although it has not been reported in the literature to our knowledge. The latter value is the same as the W-0 bond energy of 4.5 eV,22 within experimental error. These results indicate that cleavage of Fe-0 and W-0 bonds trigger the crystallization of iron-containing and iron-free tungstate glasses, respectively. In the crystallization of iron tellurite glass, 95Teo2-5Fe203, the Kissinger plot yielded an E, of 2.3 (k0.3) eV, which is comparable to the E, obtained from the JMA plot in the FTIR transmission method: i.e.2.9 (k0.3) eV.17 These E, values are comparable to the Fe-0 bond energy of 2.6 eV described above or to the Te-0 bond energy of 3.0 eV.22 This study was carried out in order to elucidate the effect of heat treatment on the structure of potassium vanadate glasses containing 10 mol% Fe203. 57Fe Mossbauer effect, FTIR, DTA and X-ray diffraction (XRD) studies were used for this purpose. The changes of the electrical conductivity, 0, and of the molar magnetic susceptibility, xm, of 25K20. 65V205-10Fe203 glass were investigated at several stages of the heat treatment in order to elucidate the relationship between the structural change and the physical properties of the material. Experimental Potassium vanadate glasses, xK20 (90 -x)V205 10Fe203, were prepared by melting weighed amounts of a reagent mixture composed of K2C03,V205 and Fe203 of guaranteed reagent grade (Ishizu Pharmaceutical Co.Ltd). The reagent mixture placed in a platinum crucible was melted at 1050°C for 1h in an electric muffle furnace, and the melt was quenched with ice-cold water. Homogeneous black glass samples were prepared in the compositional range 5<x <30. 35K20* 65V205 glass was prepared similarly after melting the reagent mixture at 900 "C. 57Fe Mossbauer spectra of heat-treated glass samples were measured at room temperature with a 57Co( Pd) source of 10 mCi (3.7 x 10' Bq). A sheet of metallic iron foil (a-Fe) enriched with 57Fe was used as the reference for the isomer shift, 6, and for calibrating the velocity scale (abscissae of the spectra).The spectral analysis was made by a least- 1890 J. Muter. Chern., 1996, 6(12), 1889-1896 squares method. FTIR spectra were measured by the conven- tional KBr disk method. The values of Tg were determined by conventional DTA conducted at a heating rate of 5 "C min-l. a-A1203 powder was used for temperature calibration. The XRD pattern was recorded at a scanning rate of 2 degrees min -'with Cu-Ka X-rays. The electrical conductivity, 0,was measured at room temperature for rectangular samples (1.0 x 5.0 x 0.8 mm3) to which lead wires were attached with an indium solder. In this paper are shown the mean values of the electrical conductivities obtained by dividing the current density (A cm-2) by the electric field (V cm-l).Each current density was obtained after 15 s had passed under constant voltage, because the system consisting of the glass sample and the contacts has a capacitance. The voltage dependence of CJ was investigated by the dc two-probe method. In order to confirm that the electrical conductivity obtained by the dc two-probe method reflects the steady-state response from the glass sample, the ac four-probe method was also used with a frequency of 1.0 Hz and a current of ca. 0.6 PA. Magnetic susceptibility measurements were performed using the Faraday method in the temperature range 80-300 K with HgCo(NCS), as the standard. Results 57Fe Mossbauer spectra of 25K20*65V205 10Fe203 glasses heat-treated at 340 "C for 0 to 2100 min are shown in Fig.1. Each spectrum is comprised of a doublet with an isomer shift, 6, of 0.38+0.01 mm s-', which indicates that iron is present in a distorted tetrahedral environment, Fe3+( Td),9-14 in both the glass and glass ceramics. The doublet peak narrows markedly after prolonged heat treatment, due to increased uniformity of FeO, tetrahedra. The decrease in the linewidth (FWHM), I-', reflects an increased uniformity of Fe-0 bond lengths and 0-Fe -0 angles in the partially crystallized glasses (i.e. glass ceramics). The decrease in r is illustrated in Fig. 2 together with the other Mossbauer parameters. The quadrupole splitting, A, shows a gradual decrease with heat treatment time, indicating an increase in the symmetry of the FeO, tetrahedra, i.e.a decrease in the distortion. Mossbauer spectra of 20K20 7OV2O5 * 10Fe203 and 30K20 60V205 10Fe203 glasses heat-treated at 370 "C for 0 and 5000min are shown in Fig. 3. The Mossbauer spectrum of non-treated 20K20 7ov20, 10Fe203 glass [Fig. 3(a)] has the -4 -3 -2 -1 0 1 2 3 4 velocity/mm s-1 Fig. 1 57Fe Mossbauer spectra of 25K20-65V20,-1OFe2O3 glass heat- treated at 340 "Cfor (a) 0, (b) 10, (c)60, (d) 600 and (e) 2100 min 0.7 -0.6 E E2$ 0.5 EE 0.4 0.3 0.2 Fig. 2 Change of the Mossbauer parameters of 25K,0*65Vz0,-10FezO, glass heat-treated at 340 "C for 0 to 5000 min. 6, isomer shift with respect to metallic iron; A, quadrupole splitting; r,line-width (FWHM).-4 -3 -2 -1 0 1 2 3 4 velocity/mm s-1 Fig. 3 Mossbauer spectra of 20Kz0.70V,0, * lOFe,O, glass heat- treated at 370 "C for (a) 0 and (b) 5000 min. Massbauer spectra of 30K,0-60V,05 lOFe,O, glass heat-treated at 370 "C for (c) 0 and (d) 5000 rnin are shown for comparison. following parameters: 6 =0.40 mm s -', d =0.62 mm s -' and r=0.49 mm s-'. The 6 value reflects tetrahedral Fe3 ions.+ The Mossbauer parameters of an intense doublet observed in the sample heat-treated at 370 "C for 5000 rnin [Fig. 3(b)] are: 6=0.40 mm s-', d=0.46 mm s-' and r=0.42 mm s-'. A weak doublet (outer one) in this sample has the parameters: 6=0.34 mm s-', d= 1.11 mm s-' and r=0.26 mm s-'. 30K20-60V205-10Fe203 glass showed a homogeneous crys- tallization which is essentially the same as the 25K20* 65V205 10Fe203 glass (Fig.1). XRD patterns of 25K20*65V205-10Fe203 glass and glass ceramics are shown in Fig. 4. Some diffraction peaks due to crystalline phase(s) appeared after the heat treatment at 340 "C for 150 rnin and the peaks became more intense with increasing heat treatment time. Almost all the diffraction peaks shown in Fig. 4(d)-(f) are assigned to the KV30, phase having a K20/V205 ratio of 0.33, which is the same as the K20/( V205 +Fe203) ratio in 25K20 65V2059 10Fe203 glass. It is known that the KV308 phase is composed of distorted 15 20 25 30 35 40 45 50 55 28/deg re es Fig. 4 XRD patterns of 25K,0.65V,05 -lOFe,O, glass heat-treated at 340°C for (a) 0, (b) 150, (c) 600, (d) 1200, (e) 2100 and (f) 5000min.Diffraction peaks marked with solid circles refer to the KV,08 phase. V05 pyramids.23 In the case of 20K20 70V205 10Fe203 glass heat-treated at 370 "C for 5000 min, the XRD study revealed a few weak diffraction peaks assigned to a K4V10027phase24 [Fig. 5(a)], in addition to several peaks due to the KV308 phase observed in 25K20-65V20510Fe203 glass ceramic [Fig. 4, 5(b)]. The XRD patterns of 30K20 60V205* 10Fe203 glass ceramic [Fig. 5(c)] and 35K20 *65V205 glass ceramic [Fig. 5(d)] prepared by heat-treatment at 370 "C for 5000 rnin showed some diffraction peaks assigned to the K3V5014 phase, in addition to several peaks due to KV308. The K3V5014 phase having a K20/V205 ratio of 0.60 is known to be composed of V04 tetrahedra and V05 pyramids.25 A higher K20 content will be associated with the appearance of the K3V5014 phase in the glass ceramics 30K20-60V205 10Fe203 and 35K20.65V2O5.The formation of V04 tetrahedra in xK20*(90-x) V205 10Fe203 glasses can be deduced from the FTIR spectra shown in Fig. 6. The stretching vibrations of V-026 and V=027 bonds in V05 pyramids were observed in the regions 850-860 and 960-1000 cm-', respectively. The stretching vibration of the V-0 bond in V04 tetrahedra28 was observed at 750-780 cm-'. Fig. 6 evidently shows that the peak intensity of the V-0 stretching mode in V04 tetrahedra increases with increasing K20 content, at the expense of V-0 bands in VO, 10 15 20 25 30 35 40 45 50 55 28/degrees Fig.5 XRD patterns of (a) 20K,O*70Vz05 -10Fe,03, (b) 25K,O. 65V205 lOFe,O,, (c) 30Kz0-60Vz05 * lOFe,O, and (d) 35K20-65V20, glass samples heat-treated at 370 "C for 5000 rnin J. Mater. Chem., 1996,6( 12), 1889-1896 1891 A IIIIIII 1000 500 1000 500 v1crn-l Fig. 6 FTIR spectra of xK20.(90-x)V,O, * 1OFe2O3 glasses (a) x = 5, (b) x=10, (c) x=15, (d) x=20, (e) x=25 and (f) x=30 pyramids This means that the fraction of VO, tetrahedra increases in the 'skeleton' structure Crystallization of 25K20*65V205-10Fe20, glass can be deduced from the FTIR spectra shown in Fig 7, because the linewidth became smaller after the heat treatment and the Fe-0 stretching band of FeO, tetrahedra'* 2o appeared at 580 cm-I Note that this peak was not observed in the iron-free potassium vanadate glass, 35K,O *65V,05, even after heat treatment at 370 "C for 5000 min The appearance of the Fe-0 stretching band in the heat-treated samples is proof that some Fe3+ ions in the glass ceramics occupy site(s) other than those of the vanadium ions, although they occupy V5+or V4+ sites in non-treated vanadate glasses The DTA curve of 20K20* 7OV2O5 10Fe203 glass illustrated in Fig 8 is comprised of three exothermic peaks due to the crystallization, designated as T,(l), z(2) and T,(3) The T,(1) peak shifted from 250 "C to 257, 262 and 267 "C, and z(2) from 343 "C to 356, 369 and 374 "C, when the heating rate was increased from 2 "C min-' to 5, 10 and 15 "C min-', respect-ively Under the same conditions, T,(3) shifted from 403 "C to vFe-O(Td) d 1000 500 1000 500 v1crn-l Fig.7 FTIR spectra of 25K20-65V20,-1OFe2O3 glass heat-treated at 340°C for (a) 0, (b) 10, (c) 60, (d) 300, (e) 900, (f) 1500, (8) 3000 and (h) 5000 min 1892 J Muter Chem, 1996,6(12), 1889-1896 100 200 300 400 500 TI'C Fig. 8 DTA curves of 20K,0*70V205-10Fe20, glass recorded at heating rates of (a) 2, (b) 5, (c) 10 and (d) 15"C min ' and T, indicate the glass-transition temperature and the crystallization peak temperature, respectively 412,425 and 429 "C The Kissinger plot shown in Fig 9 yielded three straight lines for T,(l), z(2) and T,(3), with E, values of 2 9, 2 1 and 2 9 (fO 3) eV, respectively The DTA curve of 25K,0*65V,05.10Fe203glass is shown in Fig 10, in which two crystallization peaks of q(1)and q(2) were observed The former peak shifted from 260°C to 272, 280 and 284"C, and the latter from 319 "C to 332, 340 and 344"C, when the heating rate was increased from 2"Cmin-' to 5, 10 and 15"C min-l, respectively The Kissinger plot shown in Fig 11 yielded two straight lines for z(1) and T,(2), from which E, values of 2 0 and 2 4 (+O 3) eV, respectively, were obtained The DTA curve of 30K,0.60V205-10Fe203glass shown in Fig 12 is comprised of two crystallization peaks of T,(1) and c(2) The former peak was observed at 283, 294, 300 and 304"C, and the latter at 320, 331, 338 and 342"C, when the heating rates were 2, 5, 10 and 15 "C min-', respectively The Kissinger plot shown in Fig 13 yielded E, values of 2 6 and 2 8 (fO 3) eV for T,(1) and T,(2),respectively Fig 8, 10 and 12 indicate that the exothermic peak of K(2) is commonly observed in xK20-(90-x)V205-10Fe203 glasses and its inten- sity increases with increasing K20 content The E, for the z(2) peak was increased from 2 1eV to 2 4 and 2 8 eV when 211 c -11 10 10 9 J1 3 15 17 19 21 103 KIT, Fig.9 Kissinger plot of 20K20-7oV2o5-1OFe2O3 glass, in which T,(1 ), T,(2)and T,(3)were obtained from Fig 8 E, is the activation energy for the crystallization -eT :ndo J I I I I I I ,'I 100 200 300 400 500 T/"C Fig. 10 DTA curves of 25K20. 65V205 10Fe203 glass recorded at heating rates of (a) 2, (b) 5, (c) 10 and (d) 15"Cmin-' 1.5 1.6 1.7 1.8 1.9 2.0 103 KIT, Fig.11 Kissinger plot of 25K20-65V205* 10Fe203 glass, in which T,(1) and c(2)were obtained from Fig. 10 the K20 content was increased from 20 mol% to 25 and 30 mol%, respectively. The third crystallization peak, T,( 3), was not observed in 25K20 * 65V205* 10Fe203 and 30K20 9 60V205-10Fe203 glasses because these glasses melted in this temperature range, e.g. at 430 and 380°C in Fig. 10(b) and 12(c), respectively. Glass-transition temperatures, Tg, of 220-222, 213-217 and 204-206 "C were obtained for 20K20*70V205-10Fe203 (Fig. 8), 25K20*65Vz0,-10Fe203 (Fig. 10) and 30K20*60V205 10Fe203 (Fig. 12) glasses, respectively. The decreased gradually with increasing K20 content, as is generally observed in alkali-metal oxide glasses due to a decrease in the coordination number (CN) and/or the formation of NB0.11-14 In the case of xK20.(90-x) V205.10Fe203 glasses, the decrease in Tg is ascribed to an increase in the formation of VO, tetrahedra at the expense of V05 pyramids and to the formation of NBO in V04 and FeO, tetrahedra.The results of the magnetic susceptibility measurements are shown in Fig. 14 and 15. Using the well known eqn. (2), peff =(8xm (2) the effective magnetic moments, peff, of 25K20 *65V205 -10Fe203 glass were estimated to be 5.8 and 5.5 pB at 300 and 80 K, respectively. In eqn. (2), xm and T are the molar magnetic exo 100 200 300 400 500 TI"C Fig. 12 DTA curves of 30K,0*60V205 *10Fe203 glass recorded at heating rates of (a) 2, (b) 5, (c) 10 and (d) 15 "Cmin-' 12.5 12.0 h 11.5 N.g11.0 C-10.5 10.0 1.55 1.60 1.65 1.70 1.75 1.80 1.85 103 WT, Fig.13 Kissinger plot of 30K20.60V20, 10Fe203 glass, in which T,(1) and T,(2)were obtained from Fig. 12 =t 4.5 4.0 3.550 100 150 200 250 300 350 TIK Fig. 14 Effective magnetic moment, pen, us. temperature, T, of 25K,0*65V205 10Fe203 glass obtained at low temperature (0);the curves for the same glass after heat-treatment at 340 "C for 2100 min (0)and 5000 min (+ ) are shown for comparison susceptibility and the temperature (in K), respectively. These values are representative of high-spin Fe3 , which has five + unpaired electrons in five 3d orbitals.The value of peff is consistent with the Mossbauer measurements which revealed the absorption peak due to Fe3+ with a tetrahedral symmetry: Fe3'(G). As shown in Fig. 14, the peffvalues decreased after heat treatment at 340 "C for 2100 min, and they were 5.4 and 4.0~~300 and 80 K, respectively. The peff values of at J. Muter. Chem., 1996, 6(12), 1889-1896 1893 5 ~'~l*''~l'~~~l~'~~l'~~~l"~'Iheat treatment at 380 "C for 2100 min were determined only .d Fig. 15 Reciprocal of the magnetic susceptibility, x,,, ', us temperature T,of 25K@. 65V205 * 10Fe~0, glass obtained at low temperature (0) Xm for a sample after heat-treatment at 340 OC for 2100 min (0)and 5000 min (+ ) are shown for comparison 25K20* 65V205* 10Fe203 glass ceramic prepared by heat treat- ment at 340 "C for 5000 min were 5 2 and 3 9 pB at 300 and 80 K, respectively Since the distinct decrease in the magnetic moment seems to be related to an antiferromagnetic inter- action, the reciprocal of the molar magnetic susceptibility, xrn-', was plotted us temperature (Fig 15) The intercept of the straight line obtained for the non-treated glass sample yielded a Curie-Weiss constant, 8, of -13 (& 5) K, which indicates a weak antiferromagnetic interaction in the paramag- netic phase By contrast, 25K2O-65V2O5 10Fe203 glass cer- amics prepared by heat treatment at 340°C for 2100 and 5000 min yielded 8 values of -93 and -108 (+_5)K, respect-ively Fig 15 shows that the plots of the sample treated for 2100 min deviate from a straight line in the temperature region below 130 K, probably because of the precipitation of small antiferromagnetic particles Because of this, the 8 value at -93 K was estimated from the 'linear' parts of the plots obtained in the temperature region above 130 K A sharp increase of the electrical conductlvity, Q,was observed in 25K20-65V205 10Fe203 glass after heat treat- ment at 380°C for lOmin, as illustrated in Fig 16, which indicates that the values of 0 obtained by the dc two-probe method are almost the same as those obtained by the ac four- probe methods Since the four-probe method can be applied effectively to samples with relatively high conductivities, the 0 values of non-treated glass and the glass ceramic prepared by r7 lo4 .-10-5 cn2 10-6 10-8 Fig.16 Electrical conductivitles, 6, us time, t, of 25K20-65V,O, lOFe,O, glass obtained after the heat treatment at 380 "C 0 and 0 refer to the results obtained by the dc two-probe and ac four- probe methods, respectively The error bars indicate the region of t~ values obtained by the dc two-probe method under a voltage of 0 to & 10 V, as shown in Fig 17 1894J Mater Chem, 1996, 6(12), 1889-1896 by the dc two-probe method The concordant values of obtained by the dc two-probe and ac four-probe methods indicate that the 'contact resistance' between the indium elec- trode and the surface of the glass sample can be ignored, as can be the 'polarization effect' around the electrode In order to confirm the absence of 'contact resistance', additional con- ductivity measurements were carried out by the dc two-probe method for non-treated 25K20*65V20510Fe203 glass, on which a silver film of thickness ca 100nm was deposited as the electrode by a radiofrequency (rf) sputtering method The electrical conductivity proved to be almost the same as that obtained for the samples on which the indium electrode was attached Fig 17 shows the relationship between the electrical conduc- tivity obtained by the dc two-probe method and the voltage The values of Qobtained for non-treated 25K20*65V205 -10Fe203 glass are constant irrespective of the magnitude of the voltage, 2e the glass shows ohmic behavlour By contrast, the electrical conductivities obtained for the samples heat treated at 380°C increased with increasing voltage This non- ohmic behaviour becomes pronounced with increaslng heat- treatment time The error bars given in Fig 16 represent the region of the electrical conductivities obtained from the dc two-probe method under a voltage of 0 to flOV Fig 17 shows that heat treatment of the vanadate glass at 380°C for 2100min yielded Qvalues less than the detection limit of 5 x lop8S cm-l when voltages of 2 to -3 V were applied Because of this, the electrical conductivity of the glass ceramic prepared by heat treatment at 380 "C for 5000 min could not be estimated These results indicate that the formation of an insulating phase (KV308phase) in the glass matrix results in a gradual decrease in the electrical conductivity Discussion As shown in Fig 1 and 2, the Mossbauer spectra of 25K20 65V205-10Fe20, glass showed a distinct decrease in the linewidth (FWHM) from 049 to O28mms-' and a decrease in the quadrupole splitting (A) from 061 to 0 51 mm s-' when heat treated at 340 "C These Mossbauer results indicate that a structural relaxation and a rearrange- ment of several ions took place in the distorted FeO, and VO, tetrahedra Distortion of the structural units of vanadate glasses will be reduced as a result of the 'cooperative move- ment'29of the fragments, like a cluster composed of VO,, FeO, and V05 units The fragments will migrate from one site with 10-2p"""! c J EN Fig.17 Variation of the electncal conductivity, 6 of 25K,0.65V20, * lOFe,O, glass with voltage, E, at different times, t, investigated by the dc two-probe method under a voltage, E, of 0 to +1OV Note that only the (r values exceeding the detection limit of 5x 10 * S cm-' are given and hence the central part of the results obtained after the heat treatment at 380 "C for 2100 min is depleted t=lOmin (+), 30mm (V), 60min (A), 150mm (n),600min (0), 2100 min (0),untreated glass (0) a higher energy to another site with a lower energy in the supercooled liquid state which is defined as the temperature region between the glass-transition temperature (T,)and the melting point (T,).Hence, it is expected that brief heat treatment brings about a structural relaxation of the glass matrix.By contrast, precipitation of crystalline phase(s) like KV308 becomes significant when the glass sample is heat treated at 340 "C for more than 150 min, as could be confirmed from the intense XRD peaks after heat treatment for 1200-5000 min. Since no diffraction peak was observed in the XRD study of the glasses heat treated for 10, 30 and 60 min, it is concluded that the jump of the electrical conductivity shown in Fig. 16 is due to the structural relaxation of the 'skeleton' structure, which was initially composed of distorted VO,, FeO, and VO, units. Note that a jump of the electrical conductivity was observed in the semiconducting glass before the insulating KV308 phase precipitated. As described above, the electrical conductivity of semiconducting vanadate glass is known to be due to a step-by-step hopping of the valence (3d) electrons from V4+ to V5+.Hence, the increase in the electrical conduc- tivity can be ascribed to an increasing probability of the electron hopping, which is brought about as the result of a decreasing distortion of VO,, FeO, and VO, units. Note that the mean electrical conductivity of vanadate glass was increased distinctly upon brief heat treatment before the KV308 phase precipitated. In the DTA study of 25K20.65V205.10Fe203 glass (Fig. lo), two exothermic peaks of z(1)and z(2) were observed in the regions of 260-284 "C and 319-344 "C, respect- ively. In the Kissinger plot shown in Fig. 11, two straight lines obtained for z(1) and c(2) yielded E, values of 2.0 and 2.4 (k0.3) eV, respectively.These activation energies are much smaller than the V-0 bond energy of V04 tetrahedra (4.9 eV22) and VO, pyramids (3.9 eV22). This result suggests that a cleavage of Fe-0 bonds triggers the crystallization, as was observed recently in the DTA study (Kissinger plot) of 38Na20-61 W03 57Fe203 glass," in which the Fe- 0 bond energy was estimated to be 2.6 (k0.3) eV. By contrast, the DTA study of iron-free 38Na20*62W03 glass', yielded an E, value of 4.7 (f 0.3) eV which is, within experimental error, equal to the W-0 bond energy of 4.5 eV.22 E, values of 2.0-2.4 (&0.3) eV indicate that cleavage of Fe- 0 bonds causes the rearrangement of V4+-O-V5+ bonds in the VO, and VO, units, which is directly associated with the semiconductiv- ity (electron hopping) of vanadate glass.Hence, it is considered that the electrical conductivity due to the electron hopping from V4+ to V5+ is enhanced in the less distorted skeleton structure before crystalline phases precipitated. In the non-treated vanadate glass, it is considered that FeO, units substitute VO, and hence they are identical from the structural point of view. This can be deduced from the absence of Fe-0 bands in the FTIR spectra as shown in Fig. 6 and 7(a). The FTIR study of heat-treated samples revealed a distinct peak separation between VO, and FeO, tetrahedra due to the structural relaxation [Fig. 7(b)] and to the partial crystallization [Fig.7(c)-(h)]. A decrease in the distortion of VO, tetrahedra and VO, pyramids is also deduced from the FTIR spectra. The FTIR spectra of 25K20- 65V20, -10Fe203 glass ceramics showed the absorption bands due to FeO, tetrahedra at 580 cm-', reflecting a phase separa- tion of FeO, tetrahedra from VO, tetrahedra. As a result of the precipitation of the KV308 phase composed of VO, pyramids, it is considered that the fraction of VO, and FeO, tetrahedra increases in the glass matrix because it was originally composed of VO,, FeO, and VO, units. A' systematic decrease in the effective magnetic moments, shown in Fig. 14, is ascribed to an antiferromagnetic interaction due to Fe3+ with five unpaired electrons in the 3d orbitals. This is consistent with the appearance of Fe-0 bands in the FTIR spectra of heat-treated 25K20.65V205 10Fe203 glass [Fig. 7(c)-( h)]. The linear relationship obtained for the plot of xml us. Tand the Curie-Weiss constants, 8, obtained from the intercepts of the straight lines (Fig. 15) revealed that Fe3+ ions were enriched in the paramagnetic glassy phase, not in the crystalline KV308 phase. Taking account of the XRD study (Fig. 4) that no crystalline phase was associated with the iron, the size of the antiferromagnetic 'nanocluster' or 'nanocrystal' precipitated in the glassy phase, if present, will be too small to be detected by the Mossbauer measurements because superparamagnetism is generally observed in small particles of diameter <10 nm.30 The non-ohmic behaviour of 0 observed in the heat-treated sample can be ascribed to the crystalline KV308 phase and the antiferromagnetic nanocluster or nanocrystal, because the homogeneous single phase of the vanadate glass becomes heterogeneous when the crystalline phases (particles) precipitated.Conclusions The 57Fe Mossbauer spectra of xK20.(90- x)V205 * 10Fe203 glasses (20 <x,<30) heat-treated at around the crystallization temperature (340 "C) show a simultaneous decrease of the linewidth and the quadrupole splitting, reflecting a structural relaxation and crystallization. The symmetry of FeO, tetra-hedra constituting the network structure becomes higher upon this relaxation and crystallization. Well resolved FTIR spectra are observed in the heat-treated samples due to the relaxation and crystallization.An XRD study of the heat-treated samples revealed precipi- tation of the KV308 phase with a small amount of K4V10027 or K3V5014 phases. The K20/V205 ratio (0.33) of the KV308 phase is equivalent to the K20/(V205+Fe203) ratio of non- treated 25K20. 65V20, * 10Fe203 glass. A Kissinger plot of the DTA data yielded E, values of 2.0-2.9 (f 0.3) eV for the crystallization of xK,O * (90-x)V205-10Fe203 glasses (20 <x<30), indicating that cleavage of Fe-0 bonds with a single bond energy of 2.6 eV triggers the crystallization, as was observed recently in 38Na20-6 1 W03 57Fe203 glass. The magnetic moment of 25K20-65V205 * 10Fe203 glass was decreased after heat treatment at 340°C for 2100 and 5000 min, due to an antiferromagnetic interaction of Fe3+ ions.The reciprocal of the magnetic susceptibility, zrn-', yielded Curie-Weiss constants, 8, of -13 K for non-treated glass and -93 and -108 K for 2100 min and 5000min treated samples, respectively. Upon brief heat treatment at around the crystallization temperature (380 "C), a jump of the electrical conductivity, 0, was observed in 25K20-65V205 1OFe2O3 glass from 6.3 x lo-' S cm-' to 4.3 x lop4S cm-l, which is ascribed to an increase in the probability of electron hopping from V4+ to v5+. Precipitation of the insulating KV308 phase resulted in a gradual decrease in the electrical conductivity, and it became comparable to or less than that of the non-treated glass.It is concluded that the electrical conductivity is associated primar- ily with the semiconductivity of the glassy phase at the early stages of the heat treatment, whereas it is representative of the insulating crystalline phases in the case of glass ceramics. This paper was financially supported by Mitsubishi Heavy Industries, Ltd, Daiichi Radioisotope Laboratory, and a Grant-in-Aid for Scientific Research (C). References 1 H. Sakata, M. Amano, T. Ishiguro and T. Hirayama, J. Ceram. SOC.Jpn., 1992,100,1398(in Japanese). J. Muter. Chem., 1996,6(12), 1889-1896 1895 9 10 11 12 13 14 15 16 17 18 N F Mott, Ado Phys, 1967,16,49 I G Austin and N F Mott, Ado Phys, 1969,18,41 H T Evans and S Block, Inorg Chem , 1966,7, 1808 A M Bystrom and H T Evans, Acta Chem Scand, 1959,13,377 K Jansen and G Sperlich, Phys Status Solidi B, 1973,55495 S L Segel and R B Creel, Can J Phys ,1970,48,2673 Y Dimitriev, V Dimitrov, M Arnaudov and D Topalov, J Non-Cryst Solids, 1983,57, 147 T Nishida, J Non-Cryst Solids, 1989,108,87 T Nishida and Y Takashima, Bull Chem SOC Jpn ,1987,60,941 T Nishida, J Non-Cryst Solids, 1994,177,257 T Nishida, J Radioanal Nucl Chem ,1994,182,451 T Nishida, Hyper-ne Interact, 1995,95,23 T Nishida, in Mossbauer Spectroscopy of Sophisticated Oxides, Akademiai Kiado, Budapest, 1996,ch 2 T Nishida, M Suzuki, S Kubuki, M Katada and Y Maeda, J Non-Cryst Solids, 1996,19423 T Nishida, J Muter Chem, 1992,2,733 T Nishida, S Inoue and Y Takashima, Bull Chem SOC Jpn ,1992, 65,1927 T Nishida, H Ide, T Shinmyozu, Y Takashima and Y Matsumoto, Jpn J Appl Phys, 1990,29,1293 19 T Nishida, J Radioanal Nucl Chem ,1995,190,381 20 P Tarte, in Physics of Non-Crystalline Solids, ed J A Pnns, North- Holland, Amsterdam, 1965, pp 549-565 21 H E Kissinger, Anal Chem ,1957,29, 1702 22 D Chakravorty, in Modern Aspect of Solid State Chemistry, Plenum, New York, 1980,pp 391-423 23 H T Evans and S Block, Inorg Chem ,1966,5,1808 24 V V Illanonov, R P Ozerov and E V Killdisheva, J Inorg Chem USSR, 1956,1,777 25 A M Bystrom and H T Evans, Acta Chem Scand, 1959,13,377 26 H Hirashima, T Koyama and T Yoshida, Yogyo-kyokai-shi,1985, 93,554 (in Japanese) 27 Y Dimitriev, M Arnaudov and V Dimitrov, J Solid State Chem , 1981,38,55 28 M Kurzawa, J Mater Sci Lett, 1992,11,976 29 G Adams and J H Gibbs, J Chem Phys, 1965,43,139 30 N N Greenwood and T C Gibb, in Mossbauer Spectroscopy, Chapman and Hall, London, 1971, ch 10 Paper 6/03778J, Received 30th May, 1996 1896 J Mater Chem , 1996, 6(12), 1889-1896

ISSN:0959-9428    

DOI:10.1039/JM9960601889

出版商:RSC    

年代:1996

数据来源: RSC