Thermodynamic Modeling of the HfO2–La2O3–Al2O3 System

Based on phase equilibria, thermodynamic, and crystal structure data, the thermodynamic modeling of HfO2–La2O3–Al2O3 system is presented. Liquid phase is described by the modified quasichemical model considering the short‐range ordering in liquid solution. Solid solutions are described by the ionic sublattice model considering respective crystal structure. The model (La3+, Hf4+)2(Hf4+, La3+)2(O2−, Va)6(O2−)1(Va, O2−)1 successfully describes the structure defect, homogeneity range, and thermodynamic property of pyrochlore solid solution. A set of optimized model parameters is obtained which reproduces most experimental data well. Isothermal sections, liquidus and solidus projections, and Scheil reaction scheme are constructed.