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Phase Diagram Calculations for ZrO_{2} Based Ceramics: Thermodynamic Regularities in Zirconate Formation and Solubilities of Transition Metal Oxides

H. Yokokawa, N. Sakai, T. Kawada, and M. Dokiya
[Sci. & Technol. of Zirconia V, Technomic Publishing Co., Inc. 1993, pp.59-68]

Phase diagram calculations have been made using evaluated or estimated thermodynamic properties of stoichiometric compounds and solid solutions in the ZrO_{2}-MO(M=Mg,Ca,Sr), the ZrO_{2}-M'O_{1.5}(M'=Sc,Y,La, Rare earth) and the ZrO_{2}-M"O_{2}(M"Ti,Hf,Ce) systems. An emphasis has been placed on finding thermodynamic regularities in the stability of perovskites, pyrochlore-type compounds, and fluorite-type solid solutions. Interaction parameters for the fluorite solid solutions have been found to be well correlated with ionic radii. This has been utilized to calculate the solubilities of the transition metal oxides into Y_{2}O_{3}-stabilized ZrO_{2}(YSZ). An associated solution model has been adopted to derive the respective contributions from the various valence states of the transition metal ions as functions of temperature and oxygen potential.