Combined experimental and computational investigation of thermodynamics and phase equilibria in the CaO–TiO ₂ system

Phase relations in the CaO–TiO 2 system are of considerable interest in geology, metallurgy, and ceramics. Despite a number of studies of phase equilibria in the CaO–TiO 2 system, there are still some open questions regarding the stability of intermediate compounds. In this work, a series of specimens with different CaO:TiO 2 ratios were prepared by solid‐state reaction. The heat capacities of Ca 3 Ti 2 O 7 and Ca 4 Ti 3 O 10 from 300 to 1073 K were measured by differential scanning calorimetry and their formation enthalpies from the component oxides at 298 K were measured by high temperature oxide melt solution calorimetry. Using phase diagram information and thermodynamic data from the literature and the present measurements, thermodynamic optimization of the CaO–TiO 2 system was carried out by the CALPHAD technique. The phase diagram and the thermodynamic properties of the CaO–TiO 2 system were calculated using the obtained thermodynamic database, which clarify the stable and metastable phase equilibria of the system. The thermodynamic stability of the various compounds was discussed.