Insitu observation of shear stress-induced perovskite to post-perovskite phase transition in CaIrO3 and the development of its deformation texture in a diamond-anvil cell up to 30 GPa

Abstract

The perovskite (Pv) to post-perovskite (PPv) phase transition and the deformation texture of the PPv phase were investigated on the basis of a high-pressure X-ray diffraction (XRD) study of CaIrO3 using a diamond-anvil cell in a pressure range up to 31GPa. The development of a crystallographic preferred orientation (CPO) in the PPv phase was observed after the plastic deformation from 8 or 9GPa to 31GPa at both room and high (∼1500K) temperatures. The observed CPOs in the present study indicate that the (010) plane worked as an active slip plane in the PPv phase over the entire pressure and temperature range of the present experiment. We also confirmed that the Pv to PPv phase transition proceeds at room temperature under high-stress conditions. The phase transition under high-stress condition is in stark contrast to the results of a previous hydrostatic experiment in which the Pv-CaIrO3 remained stable in a helium media at 31GPa and room temperature. This indicates that shear stress plays an important role in the Pv to PPv phase transition, and this effect should be taken into account when the thermal structure at the D″ layer is discussed on the basis of the high-pressure experiments.