Thermal analysis and prediction of phase equilibria in the TiO2–Bi2O3 system

A thermodynamic study on the TiO2–Bi2O3 system was carried out using differential thermal analysis (DTA) and X-Ray diffraction (XRD) techniques covering the composition range from 65 to 90 mol% Bi2O3. From the XRD results the only two intermediate compounds in the Bi2O3 rich region were Bi4Ti3O12 and Bi12TiO20. The Bi4Ti3O12 phase presents the well known plate-like morphology. The experimentally determined phase transition temperatures with DTA technique were compared with thermodynamic calculated results and good agreement was obtained. The DTA results also showed that the limit of the peritectic reaction between liquid and Bi4Ti3O12 occurs approximately at 90 mol% Bi2O3. The phase diagram of the TiO2–Bi2O3 system was calculated using a quasichemical model for the liquid phase. The thermodynamic properties of the intermediate compounds were estimated from the data of TiO2 and Bi2O3 pure solids. In this manner, data for this binary system have been analysed and represented with a small adjustable parameter for the liquid phase.