Thermodynamic assessment of the ZrO2–Yb2O3–Al2O3 system

A thermodynamic database for the ZrO2–Y b2O3–Al2O3 system is derived based on literature data for experimental isothermal sections at 1250 and 1650 °C, solidus and liquidus surfaces and vertical sections. The compound energy formalism and two-sublattice partially ionic liquid model are applied for phase descriptions in the system. Thermodynamic parameters for the binary systems ZrO2–Y b2O3 and Y b2O3–Al2O3 are assessed in this study, based on experimental phase equilibrium and calorimetric data for binary systems, taking into account sub-solidus and solidus phase relations in the ternary system of ZrO2–Y b2O3–Al2O3. It is demonstrated that the phase equilibria between solid phases in the ternary ZrO2–Y b2O3–Al2O3 system is an important test for mutual consistency of binary descriptions, and thus phase relations in the ternary system are used to constrain the thermodynamic parameters in the binary system Y b2O3–Al2O3. No ternary interaction parameter was necessary for the liquid phase to reproduce the experimental data on the liquidus and solidus surfaces and vertical sections. Isothermal sections at 1250 and 1650 °C, the liquidus surface and vertical sections are calculated and compared with available experimental data. The experimental data are generally well reproduced by calculations, except for the solid phase relations in the Y b2O3-rich corner.