Phase Diagrams of Ternary and Multicomponent Rare‐Earth Sesquioxide (RE ₂ O ₃ ) Systems (RE = All Lanthanides, Y, and Sc)

ABSTRACT A comprehensive CALPHAD‐based thermodynamic framework was developed to predict the phase diagrams and thermodynamic properties of ternary and multicomponent RE 2 O 3 systems using the optimized model parameters of the unary and binary RE 2 O 3 systems. The thermodynamic models for solid and liquid RE 2 O 3 solutions incorporate the interaction parameters between RE species in the solutions as a function of the ionic radius difference between REs. The developed models successfully reproduce all available ternary and multicomponent experimental data within experimental uncertainties. The present thermodynamic models can provide a consistent and extensible basis for predicting unexplored phase diagrams of ternary and multicomponent RE 2 O 3 systems and for guiding the design of high‐entropy RE 2 O 3 ceramics and other multicomponent RE 2 O 3 ‐based materials.