Phase Equilibria in the La2O3–V2O3–V2O5 System at 1200 °C

Abstract

The phase equilibria in the La2O3–V2O3–V2O5 system were established at 1200 °C by changing oxygen partial pressures from −0.68 (air) to −13.00 in terms of logPO2. In this system, 0.81La2O3·0.19V2O5(La1.62V0.38O3.38), 3La2O3·V2O5(La3VO7), 0.71La2O3·0.29V2O5(La1.42V0.58O3.58), LaVO4, LaVO3, VnO2n−1 (n=2–7), and VO2 were stable. LaVO3, LaVO4, La1.62V0.38O3.38, La3VO7, and La1.42V0.58O3.58 have nonstoichiometric compositions. On the basis of the phase equilibria, the Gibbs energies of the reactions:31⁄50La2O3+19⁄50LaVO3+19⁄100O2=La1.62V0.38O3.3850⁄31La1.62V0.38O3.38+12⁄31LaVO3+6⁄31O2=La3VO721⁄50La3VO7+4⁄25 LaVO3+2⁄25O2=La1.42V0.58O3.58LaVO3+1⁄2O2=LaVO4were determined to be −64.0, −55.8, −21.6, and −131.5 kJ respectively.