Phonon behavior of CaSnO3 perovskite under pressure

Raman scattering and x-ray diffraction studies of CaSnO3 perovskite were performed under high-pressure conditions. This high-pressure study was motivated by a recent theoretical study predicting a phase transition in CaSnO3 from GdFeO3-type perovskite to CaIrO3-type structure occurred at 12 GPa. Despite no obvious structure change up to a pressure of 26 GPa based on the x-ray diffraction data, high pressure Raman measurements revealed that some Raman modes disappeared upon compression; either merging into neighboring bands or vanishing. The signals for these Raman peaks were recovered during decompression. The measured pressure derivative of Raman shift (partial derivative v/partial derivative P) of CaSnO3 ranged from similar to 1.29 to similar to 4.35, up to 20 GPa. Due to the lack of lattice dynamic study for CaSnO3 perovskite, the mode symmetry for CaSnO3 was tentatively assigned based on the empirical relation among Ca-bearing perovskites. The pressure derivative of the Raman shifts was found to be related to their mode vibrations: modes related to Ca and O shifts had a strong pressure dependence compared with those associated with oxygen octahedral rotation. (C) 2011 American Institute of Physics. [doi:10.1063/1.3665189]