Thermodynamic Calculation of the Zirconia–Calcia System

An optimal thermodynamic data set for the zirconia–calcia system is evaluated by the CALPHAD (CALculation of PHAse Diagrams) method applied to experimental phase diagram and thermodynamic data. The liquid and C _ss (cubic ZrO₂ solid solution) are described by a subregular solution model. Three compounds, CaZr₄O₉, Ca₆Zr₁₉O₄₄, and CaZrO₃, are modeled as stoichiometric compounds. A regular solution model is applied to the other phases. Comparisons between calculated and measured phase diagrams and thermodynamic quantities show that most of experimental information is satisfactorily accounted for by thermodynamic calculations. The calculations also reasonably predict the measured electromotive force concerning the metastable C _ss.