Phase Equilibria in the Er2O3–V2O3–V2O5 System at 1200 °C

Abstract

Abstract The phase equilibria in the Er2O3–V2O3–V2O5 system have been established at 1200 °C. In this system, Er2O3, Er8V2O17(4Er2O3·V2O5), ErVO3, ErVO4, VnO2n−1(n: 2 to 7), and VO2 found to be stable, Er8V2O17, ErVO4, V2O3, and VO2 of which had non-stoichiometric compositions. On the basis of the phase equilibria, the standard Gibbs energies for the reactions, ErVO3+1⁄2O2=ErVO4, (1) 3Er2O3+2ErVO3+O2=Er8V2O17, (2) have been determined to be −121±1 and −256±1 kJ, respectively. It has been shown that the standard Gibbs energy for Sm, Er, and Lu in Eq. 1 decreases linearly with increasing ionic radius of lanthanoid.