Critical assessments and thermodynamic modeling of BaO–SiO2 and SiO2–TiO2 systems and their extensions into liquid immiscibility in the BaO–SiO2–TiO2 system

This study discusses rational reproduction of liquid immiscibility in the BaO–SiO2–TiO2 system. While a ternary assessment requires sub-binary descriptions in the same thermodynamic model, the related sub-binary systems BaO–SiO2, BaO–TiO2 and SiO2–TiO2 liquid and solid phases have been evaluated using different thermodynamic models in the literature. In this study, BaO–SiO2 and SiO2–TiO2 were assessed using the Ionic Two Sublattice model (I2SL) based on experimental data from the literature. BaO–TiO2 was already assessed using this model. Binary descriptions developed were then used for the assessment of liquid immiscibility in the BaO–SiO2–TiO2 system. Ternary interaction parameters were found necessary for rational reproduction of the new ternary experimental data gathered in the present work. The model parameters for each system were evaluated using a CAPLHAD approach. A set of parameters is proposed. They show good agreement between the calculated and experimental equilibrium liquidus, liquid immiscibility and thermochemical properties in the BaO–SiO2–TiO2 system.