Abstract
To prove the feasibility of pyrometallurgical recovery of the rare earth elements, it is necessary to understand the thermodynamic properties of related rare earth oxides containing systems. Based on the experimental data as well as thermodynamic modelling of the silicate subsystems, a thermodynamic description of CaO-Gd2O3–SiO2 ternary system is constructed. The Gibbs energy of the liquid phase is modeled by the Modified Quasichemical Model. The solid phases are modeled by the polynomial expansions of the excess Gibbs energy. The present modelling ternary phase equilibria are in good agreement with the experimental data in the literature.