THERMODYNAMIC EVALUATION FOR THE Y2O3-BAO-CUOX SYSTEM

The thermodynamic data for the Y2O3-BaO-Cu2O-CuO quaternary system were optimized from measured thermodynamic data. A two-sublattice model for ionic solution was used to express the Gibbs free energy of the liquid phase, and a two-sublattice regular solution model was used for the nonstoichiometric YBa2Cu3O6+delta superconducting compound. The optimized thermodynamic data were used to calculate the phase diagrams of the Cu2O-CuO binary system and the CuO(x)-Y2Cu2O5 and CuO(x)-BaCuO2 quasi-binary systems. The results were in good agreement with reported measured data. The liquidus projection and isothermal and vertical sections of the Y2O3-BaO-CuO(x) quasi-ternary system were calculated. The effect of oxygen pressure on some reaction temperatures was predicted by calculating them at various oxygen pressures, and the oxygen contents (6 + delta) in YBa2Cu3O6+delta were calculated at various temperatures and oxygen pressures. The results were compared with experimental data.