Re-evaluation of the thermodynamic equilibria on the zirconia-rich side of the ZrO2-YO1.5 system

The thermodynamic database of ZrO2-YO1.5 system, which has been extensively studied by many groups, was reassessed and improved particularly on the ZrO2-rich side of the system. Due to sluggish kinetics and diffusionless transformations in the ZrO2-rich side of ZrO2-YO1.5 system, providing accurate phase diagram and thermo-chemical data had become problematic. The newly developed thermodynamic database shows well agreement with the related experimental data, which were wisely evaluated and carefully selected to ensure the accuracy of the developed database. Applying the CALPHAD (CALculation of PHAse Diagrams) approach, the interaction parameters of the cubic, tetragonal, monoclinic, and liquid phases were optimized to develop a complete and self-consistent thermodynamic description of the ZrO2-YO1.5 system. The Gibbs energy model for the monoclinic phase was also modified to a regular solution. The improved thermodynamic database of the ZrO2-YO1.5 system can give more accurate modeling results, especially for the ZrO2-rich side of the system, which has critical applications.