ISSN:0005-9021    

DOI:10.1002/bbpc.19890930202

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe electronic conductivity, σe, and the Hall coefficient,RH, of the high‐temperature phase of silver selenide, β‐Ag2+δSe, are experimentally determined at temperaturesTbetween 170° and 300° and at values of σ covering the entire stability range. The change of composition is achieved and monitored by in situ coulometric titration. The electronic transport data yield the following results. The conduction band is harmonic, whereas the valence band is anharmonic. Mobility and relaxation time of conduction‐band electrons vary with temperature asT−1and with the electronic energy as ϵ−1/2. This is the behaviour normally assumed to be valid, if the relaxation is due to the scattering of electrons by

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930203

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractIn a previous paper (I) we presented the composition dependent electronic conductivity and Hall coefficient of β‐Ag2+δS at different temperatures. The mobility of conduction‐band electrons was found to vary with temperature asT−3/2. In this paper we point out that, due to a temperature dependent effective electron mass, the relaxation time of conduction‐band electrons varies asT−1and

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930204

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe thermodynamic properties of electrons in cuprous selenide was studied with the help of coulometric titrations, using the solid state galvanic cell. ‐ Pt/Cu/CuBr/Cu2‐δSe/graphite, in the temperature region between 350 and 450°. The electromotive force (emf) of this cell was measured as a function of the stoichiometry of the selenide compound and the temperature. Analysis of the experimental data shows that the semiconducting properties of cuprous selenide and the change of the thermodynamic quantities with composition are only given by a change of the respective quantities of the defect electrons or of the quasifree electrons. From the electrochemical measurements besides of other quantities —the band gap energy can be calculated and is of about

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930205

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractUsing several experimental techniques (electrical conductivity measurement, differential thermal analysis and differential enthalpic analysis), the Li2UCl6, Na2UCl6and Cs2UCl6Compounds have been investigated. —The joint examination of thermograms and phase diagrams suggests that the fusion of Li2UCl6and Na2UCl6compounds is preceeded by small thermal effects which are not always reproducible. —Melting temperatures and enthalpies of transformation and fusion have been measured:These new results were compared with those previously found for similar compounds. The calorimetric and electrical experimental values obtained for Li2UBr6and Li2UCl6allowed a parallelity to be established: the very close values of entropy of fusion, 61 and 57 J · mol−1· K−1, respectively, suggest that the melting mechanism is similar for both compounds. —On the other hand, in spite of similar entropies of fusion, Li2UCl6and Na2UCl6exhibit a strongly different behaviour of the electrical conductivity. The electrical properties of Li2UCl6, Na2UCl6and Cs2UCl6were also tentatively compared with those of Li2UBr6and Na2UBr6but only a qualitative interpretation can be put forward. —However the similar premelting effects and entropies of fusion (13.8 and 15.8 J · mol−1· K−1respectively) found for Na2UBr6and Cs2UCl6suggest a similar melting mechanism for both compounds. Therefore high temperature structural investigations would be essential and the clue to the electrical and thermodynamic behaviours of Li2UCl6,

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930206

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe low temperature (7–15 K) absorption spectrum of IrCl2‐6doped in single crystals of potassium and ethylammonium hexachloro‐Sn(IV) salts, A2SnCl6, recorded at high resolution supplies further contributions to solving the assignment problem of vibrational progressions of charge transfer and ligand field spin‐orbit states. The vibrational fine structure indicates differences in vibronic coupling compared to the cubic

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930207

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractNH4TaWO6, ND4TaWO6,and NH4NbWO6have been studied by NMR at various frequencies and over a large range of temperatures. At low temperatures, ammonium ions exist as an entity tunnelling in the center of the cavities of the pyrochlore framework. From relaxation data an activation energy of this process of about 6.5 kJ/mol is obtained for all three materials. At temperatures above about 250 K translational motion narrows the spectra and produces relaxation. The experiments suggest a Grotthus type of proton transfer, where both local back ‐ and forth‐hopping (13–20 kJ/mol) and long range migration (31–39 kJ/mol) plays a role. At higher temperatures NH4+and NH3may diffuse as a whole. This is shown in particular for NH4NbWO6which served as diaphragm in a water vapour electrolysis cell, and where ammonia becomes exchanged b

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930208

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe solubility of hydrogen in the intermetallic compounds Pd2Er5, Pd2Er3, PdEr, Pd4Er3, and Pd3Er has been measured by the pressure reduction method in the ranges 1 ≤P/mbar ≤ 1000 and 473 ≤T/K≤ 1148. The partial molar enthalpy of solution at infinite dilution (ΔH0H) and the partial molar excess entropy of solution at infinite dilution (ΔSE0H) have been determined from the α‐phase solubility isotherms. |H0H| is found to decrease with increase of palladium content in the following order: Pd2Er5(‐71.8 kJ ‐ mol−1), Pd2Er3(–61.0 kJ ‐ mol−1), PdEr (‐18.9 kJ · mol−1), and Pd4Er3(‐9.2 kJ · mol−1). In Pd3Er, however, ΔH0His −45.1 kJ · mol−1. The extrapolation of ΔH0H, =f(xEr) in solid solution of erbium in palladium to xEr= 0.25 gives ΔH0H= –37.3 kJ · mol−1, whereas, ΔH0H= –45.1 kJ · mol−1is observed in Pd3Er, indicating that the formation of the ordered structure results in an additional increase of exothermicity of hydrogen absorption reaction. The increase of exothermicity of hydrogen absorption in Pd3Er when compared to PdEr may be attributed to the smaller octahedral interstitial hole size. ΔSE0His found to lie between −59.0 and −64.0 J · K−1· mol−1. Pd2Er5, Pd2Er3, and PdEr show decomposition reactions by which erbium hydride and the next intermetallic compound in the Pd–Er phase diagram with less content of erbium are formed. The decomposition pressure at any temperature is found to increase with increase of palladium content, suggesting that the stability of the compounds increases with increase of palladium content at least till PdEr. The heats of formation of Pd2Er3and Pd4Er3have been ob

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930209

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractProton magnetic resonance measurements were carried out on hydrogenated samples Ti3SbHx, at different hydrogen concentrations in the range 0.3 ≤x≤ 1.74. From a comparison of the experimental second moment of the1H NMR line with the calculated one it was inferred that hydrogen occupies the tetrahedral interstitial sites surrounded by Ti atoms in the Ti3Sb lattice. The influence of temperature in the range 100 ≤T/K≤ 300 on the1H NMR in some of the hydrides showed the occurrence of motional narrowing from which the correlation frequency (vc), activation energy (Ea) and diffusion coefficient (D) were evaluated as 104Hz, 0.10 eV, and 10−12cm2/s, respectively. It was found that the hydrogen diffusion is easier in the Ti3Sb lattice compared to other Ti bas

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930210

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractUV/VIS spectroscopic studies with cold condensed silver chloride films are reported. During annealing of these films, an exciton band grows out of an initially contourless broad absorption edge. From the temperature dependence and from the time behavior of this absorption it is concluded, that the noncrystalline state of the chloride, which is formed during the condensation, is a metastable phase. The transition to the crystalline state is of an order>1. A small red shift of the maximum of the exciton band during the transformation indicates that the crystalline nuclei grow during this process.

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930211

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY