Thermodynamical models for phase changes between tetragonal and cubic phases in zro₂-ceo₂ solid solution

The Gibbs energies of cubic (c-) and tetragonal (t-) phases in pseudobinary solid solutions of Zr_1-xCe_xO₂ were assessed by two models. A regular solution model in which the Gibbs energy differences between c- and t-phases of end members were assumed to be linear functions of temperature, could not explain simultaneously the stable and metastable phase diagrams. A mathematical expression on the basis of Landau’s theory for the second-order phase transition explained both of them.