Lattice preferred orientation in CaIrO3 perovskite and post-perovskite formed by plastic deformation under pressure
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Lattice preferred orientations (LPO) developed in perovskite and post-perovskite structured CaIrO3 were studied using the radial X-ray diffraction technique combined with a diamond anvil cell. Starting materials of each phase were deformed from 0.1 MPa to 6 GPa at room temperature. Only weak LPO was formed in the perovskite phase, whereas strong LPO was formed in the post-perovskite phase with an alignment of the (010) plane perpendicular to the compression axis. The present result suggests that the (010) is a dominant slip plane in the post-perovskite phase and it is in good agreement with the crystallographic prediction, dislocation observations via transmission electron microscopy, and a recent result of simple shear deformation experiment at 1 GPa–1,173 K. However, the present result contrasts markedly from the results on MgGeO3 and (Mg,Fe)SiO3, which suggested that the (100) or (110) is a dominant slip plane with respect to the post-perovskite structure. Therefore it is difficult to discuss the behavior of the post-perovskite phase in the Earth’s deep interior based on existing data of MgGeO3, (Mg,Fe)SiO3 and CaIrO3. The possible sources of the differences between MgGeO3, (Mg,Fe)SiO3 and CaIrO3 are discussed.
KeywordsPost-perovskite CaIrO3 High-pressure Lattice preferred orientation
This paper was improved by the constructive comments of two reviewers, J. Ando and anonymous reviewer, and we deeply appreciate their efforts. This work has been performed under the approval of the Photon Factory Program Advisory Committee (Proposal No. 06G047).
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