[en] The phase equilibria in the systems V₂O₃-VO₂ and VO₂-V₂O₅ were established by varying the oxygen partial pressures from 10^-3 to 10^-12 atm in the former system at the temperatures from 1307 to 1700K and in the latter from 773 to 934K, respectively. The stability regions of the vanadium oxides with respect to the oxygen partial pressures were determined by means of quenching, thermogravimetric and EMF methods. The oxygen partial pressures were measured using a solid electrolyte cell composed of (ZrO₂)sub(0.85)(CaO)sub(0.15). Eight phases, V₂O₃, V₃O₅, V₄O₇, V₅O₉, V₆O₁₁, V₇O₁₃, V₈O₁₅ and VO₂ were found to be stable at 1307K. The phases, V₇O₁₃ and V₈O₁₅, and V₇O₁₃, V₈O₁₅ and V₅O₉, however, could not be observed at 1600 and 1700K, respectively. The four phases, VO₂, V₆O₁₃, V₃O₇ and V₂O₅, existed in stable at the temperatures from 773 to 934K. The only phases of V₂O₃ and V₆O₁₁ had extensive homogeneous range due to nonstoichiometry. The pressure-composition isotherm may be explained in terms of metal vacancies. The tentative phase diagrams with isobaric lines of oxygen partial pressures in respective of the systems V₂O₃-VO₂ and VO₂-V₂O₅ were determined. The standard free energy, enthalpy and entropy data of the oxidation reactions between the intermediate oxide phases were evaluated on the basis of the equilibrium oxygen partial pressures. (auth.)

[en] The oxidation of Mo₆S₈ was studied under isothermal and nonisothermal conditions by thermogravimetry in air. The oxygen incorporation into Mo₆S₈ at 300 C is controlled by diffusion. The diffusion coefficient of oxygen in Mo₆S₈ was evaluated as (4 ± 1.0) x 10^-14 cm²/sec at 573 K. (author). 24 refs, 10 figs, 3 tabs

[en] An equilibrium isotherm on V-S system at 900 ⁰C was determined by changing partial pressure of sulfur. Single crystals of several V₅S₈ and V₂S₃ compounds were grown by chemical transport. The grown crystals almost satisfied compositional relation on equilibrium isotherms between 900 ⁰C (hot zone) and lower temperatures (cold zone). Electrical conductivity of the single crystals was measured at temperatures from liquid nitrogen to 25 ⁰C. It showed metallic behavior without any significant dependence on compositional variation. Also the conductivity measurement of sintered samples for various vanadium sulfides was carried out in the compositional range from VSsub(1.38) (V₃S₄ phase) to VSsub(1.58) (V₅S₈ phase). (author)

[en] Chevrel phases of the type M/sub x/Mo/sub 6/S/sub 8-9/ (M = metal ion) are an important class of compounds because of their interesting structural, superconducting, and magnetic properties. Attempts are also being made to exploit the possibilities of their use as electrode material. Some investigators used bulk specimen or pellets of one of the Chevrel phases, copper molybdenum sulfides (CMS), as a rechargeable cathode material for lithium secondary batteries. A porous thin film of CMS would be suitable as an electrode in developing a high energy compact secondary battery. CMS thin films are usually prepared by a dc getter sputtering method or by an evaporation technique. However, films produced by any of these methods often contain an impurity phase other than the pure CMS phase. A new technique of preparing porous and coherent thin films of CMS on Cu/sub 2/S has been developed. The preparation technique and the properties of the film, along with the results of incorporation of Li/sup -/ ion into this film, are presented in this paper

[en] Lead molybdenum sulfides Pb /sub x/ Mo₆S /sub 8-y/ with rhombohedral structure were prepared by vacuum seal technique at 1000⁰C. The nonstoichiometric range of lead (x) varies between 0.95 and 1.05, and that of sulfur (8-y) varies between 7.55 and 7.80. On the basis of these results and preparing some mixed compounds, the phase diagram of Pb-Mo-S system at 1000⁰C was established. The compositional dependence of the rhombohedral lattice parameters a /sub R/ and α /sub R/ and that of the superconducting critical temperature Tc of the single phase of Pb /sub x/ Mo₆S /sub 8-y/ have been examined. It was difficult to find out the compositional dependence of a /sub R/ and α /sub R/ and that of Tc, because of the narrow ranges of the nonstoichiometry. Among the nonstoichiometric compounds, Pb /sub 0.95/ Mo₆S₇^-₅₅ shows the highest Tc (Tc-ON=15.5K, Tc-END=13:9K). From the measurement of normal state resistivity, all the compounds of the Pb /sub x/ Mo₆S /sub 8-y/ showed the properties of metallic conductors

[en] Secondary electrochemical cell based on intercalation system might be of practical importance if the cell voltage, energy density and cycle life are favourable. Recently large number of chalcogenides with three dimensional framework like molybdenum cluster sulfides M/sub y/Mo/sub 6/S/sub 8-z/ (Chevrel phase) have been examined as the cathode material for secondary organic electrolyte lithium batteries. Copper molybdenum sulfide Cu/sub y/Mo/sub 6/S/sub 8-z/ (CMS) is one of such intercalation host material which is composed of nearly cubic Mo/sub 6/S/sub 8/ building blocks. It is highly expected that porous thin films CMS, if possible to prepare effectively, would act as a suitable electrode for developing a compact battery with high energy capacity. In the present study, the CMS films prepared by the technique of painting and subsequent sintering reaction were tested as the cathode for lithium secondary battery using organic liquid electrolyte, and also the mechanisms of lithium intercalation into the films were investigated by the O.C.V. measurement and X-ray powder diffractometry

[en] This paper reports on the single-phase region of cobalt Chevrel-phase compound (Co_yMo₆S_8-z:CoCP) determined by x-ray diffraction analysis. The nonstoichiometric range of CoCP was very narrow and the only CoCP with y = 1.6,8 - z = 7.7 could be prepared as a single phase. The CoCP was evaluated as a cathode for lithium secondary batteries. 1M CiClO₄ in PC was used as an electrolyte. The discharge properties and discharge-charge cycling properties were measured galvanostatically under constant current densities from 0.1 to 2.0 mA/cm². The cell exhibited good discharge performance; for example when the cell was discharged under a cd = 0.1 mA/cm², 4.8 Li/Co_1.6Mo₆S_7.7 were incorporated before the cell voltage fell down to 1.0 V (energy density: 277 Wh/kg). Also a rechargeability of more than 200 cycles was observed at cd = 0.5 mA/cm². The curve of OCV with varying Li content in the CoCP was very flat and near 2.1 V. The x-ray analysis of lithium incorporated cobalt Chevrel phase, Li_xCoCP, was two sets of hexagonal lattice parameters showing the existence of two types of Chevrel phases (having different lattice parameters) coexisting in a wide range of 0 < x < 4.5

[en] The sulfur gas potentials in the H/sub 2/S + H/sub 2/ buffer gases were measured by a galvanic cell Ps/sub 2/(g),Au(Pt)/(MoS/sub 2/ + CaS)/CaF/sub 2//(Cu + Cu/sub 2/S + CaS)/Au(Pt) in the temperature range from 650⁰ to 950⁰C and Ps/sub 2/ region from 10/sup -2/ to 10/sup -10/ atm. A quick response time (within 5 to 10 min) in emf with the change of Ps/sub 2/ at a given temperature was observed by placing a MoS/sub 2/ and CaS mixed pellet auxiliary electrode at the bottom of the cylindrical single-crystal CaF/sub 2/ electrolyte. The observed emf's agreed well with with those calculated from the Nernst equation. Using this sensor, Ps/sub 2/ values in the SO/sub 2/ + H/sub 2/ + H/sub 2/S gas system were also evaluated from the measured emf at 827⁰C and were found to be in close agreement with those calculated from the thermochemical tables