Pressure-Induced Phase Transition and Structural Evolution of Single-Crystal CaSnO3 Perovskite

Abstract

Calcium stannate (CaSnO3) is a widely used analogue of bridgmanite (MgSiO3), capable of undergoing a pressure-induced perovskite-to-postperovskite phase transition under accessible experimental conditions. In this study, high-quality single-crystal CaSnO3 perovskite was synthesized by solid-state reaction. Its structural behavior at pressures up to 50.0 GPa was investigated using diamond-anvil cells combined with in situ synchrotron X-ray diffraction, Raman spectroscopy, and first-principles calculations. X-ray diffraction analysis identifies the onset of the phase transition at 17.1 GPa, while Raman spectroscopy provides complementary evidence through the emergence of a new vibrational mode at 18.3 GPa. Furthermore, theoretical calculations confirmed the thermodynamic stability of the postperovskite phase above 17.0 GPa, corroborating the experimental findings. Due to its comparable axial ratio and more readily achievable pressure–temperature conditions relative to MgSiO3, CaSnO3 serves as an excellent low-pressure analogue for elucidating the properties and dynamics of the deep Earth’s interior.