Thermodynamic Assessment And Experimental Investigation Of BaO-SrO-TiO₂-ZrO₂ System

Using CALPHAD technology, the thermodynamic optimization and calculation of the pseudo-binary subsystems ZrO2-TiO2, ZrO2-SrO, ZrO2-BaO and SrO-TiO2, and pseudo-ternary subsystems BaO-SrO-TiO2, BaO-TiO2-ZrO2 and SrO-TiO2-ZrO2 were made, the BaO-SrO-ZrO2 pseudo-ternary system and BaO-SrO-TiO2-ZrO2 pseudo-quadruple system were thermodynamically extrapolated. The liquid and reciprocal phases included in pseudo-quadruple system have also been calculated. Sub-stitutional solution model for solutions and line compounds, Neumann-Kopp Rule for stoichiometric compounds, compound energy formula for defect distortional ZrTiO4 and SrTiO3 were adopted. Stable and meta-stable phase equilibria and various thermodynamic properties are calculated and compared with the corresponding measurements. A set of self-consistent thermodynamic parameters reproducing most of experimental data on phase diagram and thermodynamic properties within the reported uncertainties has been obtained. Guided by the present calculated phase diagrams, the microwave dielectric properties of BaTi4O9/Ba2Ti9O20 system was investigated, and the best properties were obtained by adding about 2.5mol%SrO and 6mol%ZrO2.