Phase Equilibria in the V2O3–VO2 System at High Temperatures

概要

論文の詳細を見る
The phase equilibria in the V2O3–VO2 system were established at 1307 K by varying the oxygen partial pressures from 10−4 to 10−12 atm. Eight phases, V2O3, V3O5, V4O7, V5O9, V6O11, V7O13, V8O15, and VO2, were observed under these experimental conditions. Vanadium sesquioxide has an extensive range of solid solutions at 1307 K. Also, the phase diagram and isobaric lines of oxygen partial pressure in the V2O3 phase were determined from 1307 to 1700 K on the basis of our present and previous studies. Quenching and thermogravimetric methods were applied under a controlled oxygen atmosphere. The oxygen partial pressures were determined by means of a solid electrolyte cell composed of (ZrO2)0.85(CaO)0.15. The standard free energies of the oxidation of V2O3 to V3O5, of V3O5 to V4O7, of V4O7 to V5O9, of V5O9 to V6O11, of V6O11 to V7O13, of V7O13 to V8O15, and of V8O15 to VO2 were determined on the basis of the equilibrium oxygen partial pressure at 1307 K. The enthalpy and entropy data of the oxidations of V2O3 to V3O5 and of V3O5 to V4O7 were evaluated from the oxygen partial pressures on the basis of the present results and previous data.
公益社団法人日本化学会の論文