High-temperature heat capacity and phase transitions of CaTiO₃ perovskite

Abstract

Drop-calorimetry measurements performed on CaTiO₃ perovskite between 400 and 1800 K have shown the occurrence of two overlapping phase transitions at 1384 and 1520 K. The 1384 K transition shows a λ-type C _p variation with a very sharp C _p decrease after the transition; in contrast, the 1520 K transition exhibits a unusual λ shape with a long high-temperature tail spanning more than 400 K. By comparison with previous structural studies, we suggest that the 1384 K transition may be due to an orthorhombic Pbnm to orthorhombic Cmcm transition and that the peak centered at 1520 K represents the effects of overlapping orthorhombic to tetragonal and tetragonal to cubic phase transitions. The large anomaly of specific heat above 1520 K suggests that the cubic phase produced may be strongly disordered up to the melting point.