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

Compressional (P) and shear (S) wave velocities of CaSnO3 perovskite were measured at room temperature using ultrasonic interferometry up to 18GPa. 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 0-18GPa range.