Assessment of thermodynamic functions in the ZrO 2–Nd 2O 3–Al 2O 3 system

Abstract

The thermodynamic database for the ZrO 2–Nd 2O 3–Al 2O 3 system is derived using the Calphad approach. The compound energy formalism and two-sublattice ionic liquid model are applied for phase descriptions in the system. Thermodynamic parameters for the ZrO 2–Nd 2O 3 and Nd 2O 3–Al 2O 3 systems are assessed in this study with special attention to triangulation in the ternary system of ZrO 2–Nd 2O 3–Al 2O 3. It is demonstrated that the phase equilibria between solid phases in the ternary ZrO 2–Nd 2O 3–Al 2O 3 system constrain thermodynamic parameters in the binary systems ZrO 2–Nd 2O 3 and Nd 2O 3–Al 2O 3. The ternary interaction parameter is assessed for the liquid phase using experimental data on the liquidus surface. Isothermal sections at 1523 and 1923 K, the liquidus surface and several vertical sections are calculated and compared with available experimental data. Several inconsistencies between calculations and experimental data occur because the calculations reveal the existence of a primary crystallisation field for pyrochlore.