摘要:

AbstractC8H12O3N2,Mr= 184.19, Trigonal, R3 (hexagonal axes)a=b= 26.800(1) Å,c= 6.828(3) Å, α = β = 90°, γ = 120°,V= 4247.11 Å3,Z= 18,Dm= 1.297 Mg m−3,Dc= 1.296 Mg m−3,mu= 0.79 mm−1,F(000) = 1764,T= 293 K, finalR= 0.080 for 1205 observed reflections. There are two crystallographically independent molecules in the unit cell of the t

ISSN:0232-1300    

DOI:10.1002/crat.2170300619

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSingle crystals of sarcosine barium chloride tetrahydrate were crystallised from a saturated aqueous solution containing stoichiometric amounts of sarcosine and barium chloride, in 2: 1 proportion. The intensity data were collected using a CAD‐4 diffractometer with graphite monochromated MoKα radiation. The crystal data are as follows:a= 7.235(1) Å,b= 10.668(4) Å,c= 15.686(3) Å,V= 1210.7 Å3,F.W.= 369.33,dexpt, = 2.02 g · cm−3,dcalc= 2.026 g · cm−3,Z= 4 and the space group is P212121. The structure has been solved to anRvalue of 0.02 for all the 1239 reflections withI>2σ(I). The sarcosine molecule exists as zwitterion in the structure. The barium ion is found to have 10‐fold coordination with nine oxygens and a chlorine taking part in coordination. All the water oxygens and chlorines take part in hydrogen bonds except c

ISSN:0232-1300    

DOI:10.1002/crat.2170300620

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe saccharin (o‐sulphobenzoimide) crystal is synthesized and its crystal structure has also been determined. Saccharin, as a ligand, can be coordinated with a metal ion in different modes. The variations of the saccharin molecular structure in different coordination environments are studied. As the saccharin molecule takes part as ligand or anion, its molecule structure will take some obvious changes. The factors of these changes may mostly be due to the coordination environment and hydrogen bond. The effects of different coordinated metal ion and different coordination mode are very smal

ISSN:0232-1300    

DOI:10.1002/crat.2170300621

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe positron lifetime spectra in Y‐doped (Ba0.6Sr0.4)TiO3ceramics have been measured at room temperature for Y contents of 0–0.8 at. %. It was found from the experiments that with increasing Y content, the variation of the positron lifetime parameters is nonmonotonic, and the Y content corresponding to the knee is about 0.7 at. %, which is much larger than the La content corresponding to the knee in the La‐doped BaTiO2(TANG 1994a). The experimental results show that the Y ions substitute predominantly for Sr ions, and this substitution induces a large number of Sr vacancies; when the Y content increases to about 0.7 at. %, the Y ions begin to substitute for Ba ions, and then the associated defects (2 YBaV“SrSr) and (2 YSrV”BaBa) form

ISSN:0232-1300    

DOI:10.1002/crat.2170300622

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study deals with the production of hydroxyapatite, in particular following the transformations that are involved when it is synthesized at the proximity (95 °C) of boiling temperature of water with or without a ripening treatment. Previous studies about the degree of crystallization showed that it increases with the temperature.This work is furthermore concerned about the quality of the obtainable ceramic with the use of synthetic hydroxapatite prepared by precipitation from aqueous solution. In particular the higher the degree of crystallinity, the lower the presence of spurious phosphates during sintering. The main structure‐related parameters were evaluated as a function of annealing temperature, and possible interpretations given thorough

ISSN:0232-1300    

DOI:10.1002/crat.2170300623

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractOptical absorption spectrum of Co2+ions doped in lithium sodium potassium sulphate single crystal has been studied at room and liquid nitrogen temperatures. The observed bands are assigned as transitions from the ground4T1g(F) to various excited quartet and doublet levels of Co2+ion in octahedral symmetry. The splitting in one of the bands at liquid nitrogen temperature has been explained as due to spin‐orbit interaction. All the observed band positions have been fitted with the parametersB,C,Dqand

ISSN:0232-1300    

DOI:10.1002/crat.2170300624

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe microhardness of PbTe, PbSe, EuS and EuSe has been determined. The microhardness vs lattice constant plot for chalcogenides is a curve similar to the one for alkali halides. The Gilman‐Chin parameter (H/C44) has been calculated for a large number of crytals with NaCl structure. There is no unique value representing the entire group of crystals, the values ranging from 0.01 to 0.20.The Gilman‐Chin parameter broadly correlates with the effective ionic charge (e) indicating that it is a measure of the ionicity. Empirically, it is observed that the product (H/C44) · (e)2is approximately cons

ISSN:0232-1300    

DOI:10.1002/crat.2170300625

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSingle crystals of Ga2Se3were prepared by a technique based on the Bridgman method. Thermoelectric power was investigated in the temperature range 160–525 K. From this investigation many physical parameters such as effective masses of charge carriers, carrier mobilities, diffusion length, diffusion coefficient, and the relaxation time for both majority and minority carriers were estimated. In conjunction with the electrical conductivity and the charge carrier concentration, the thermoelectric power is discusse

ISSN:0232-1300    

DOI:10.1002/crat.2170300626

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractLead titanate thin films were prepared in‐situ by RF magnetron sputtering method in the substrate temperature region of 550 °C ˜ 650 °C using Ti and Pb metal targets and oxygen gas. The films deposited at 650 °C for 60 min – when the applied power to the Ti and Pb target and deposition pressure were 200 W, 40 W, and 1.8 × 10−2Torr, respectively — had stoichiometric composition ratio and shown X‐ray diffraction patterns of tetragonal structure like that of the powder.For the application to the piezoelectric field effect transistor (PI‐FET), the substrate of SiO2(50 nm)/p‐Si(100) was used. Leakage current density of the thin film was 7 × 10−8A/cm2at 100 kV/cm, dielectric breakdown voltage was 1.8 MV/cm, and so it showed high insulator characteristics. Capacitance‐voltage curve was measured as a function of pressure. The variation width of the capacitance was 6.5 pF at bias voltage of –4 volts, and the value increased linearly according to the pressure up to about 6 kgf/cm2, and was saturated at

ISSN:0232-1300    

DOI:10.1002/crat.2170300627

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170300601

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY