Searching for post-perovskite transition in CaSnO₃ at high pressure: an ultrasonic velocity study to 18 GPa

Abstract

Compressional (P) and shear (S) wave velocities of CaSnO₃ perovskite were measured at room temperature using ultrasonic interferometry up to 18 GPa. Discontinuities of the magnitude suggested in previous theoretical calculations are not observed in derived velocities over the entire experimental pressure range explored here. A least squares fitting of the P and S wave velocities to third-order finite strain equations yielded zero pressure adiabatic bulk and shear moduli and their first pressure derivatives, K=166(2) GPa, K′=5.4(2), G=88(1) GPa and G′=1.2(1). These results are in agreement with previous experiments, within mutual uncertainties. Examinations of the current data as well as comparison with previous measurements at lower pressures conclude the presence of a post-perovskite phase transition in CaSnO₃ is not visible in the elasticity at ambient temperature within 0–18 GPa range.

Keywords:

• CaSnO₃ perovskite
• elasticity
• ultrasonic interferometry
• high pressure
• post-perovskite

Acknowledgements

The authors would like to thank Leonie Jones for hot-pressing the polycrystalline specimen used in this study in the laboratory of A.E. Ringwood at the Australian National University 17. We also thank Colin Wilson for the data analysis of alumina buffer rod travel time. The current research is jointly supported by the REU program of Mineral Physics Institute (EAR0453447) and NSF grant to BL (EAR0635860). MPI publication No. 471.