Thermodynamic evaluation of the BaO-ZrO2-YO1.5 system

Based upon the experimental data available in the literature and present measurements, thermodynamic reassessments were initially performed on the binary BaO-ZrO2, BaO-YO1.5 systems, and the resultant thermodynamic parameters were then merged in combination with that of the previous ZrO2-YO1.5 system to derive a self-consistent thermodynamic description for the ZrO2-BaO-YO1.5 ternary system with limited ternary thermodynamic parameters. The Gibbs energies of all the liquid and terminal solid solution phases were treated by the substitutional solution model, the BZ phase featured by second solid solution described by the compound energy formalism (CEF) model, and the stoichiometric compound BZY424 and Ba2YZrO6-d modeled following the Neumann-Kopp rule. The calculated results agree well with the isothermal sections at 1600 °C and 1750 °C (1873 K and 1923 K) from both of the previous and present measured phase diagrams. This demonstrates that the thermodynamic parameters derived in the present work could be applicable to compositional optimizations of novel refractories for melting titanium alloys on the basis of this ternary oxide system.