HR: 1340h
AN: MR23B-0051    [Abstracts]
TI: High-pressure phase of CaIrO₃-type Al₂O₃: implications for electrical conductivity of the lower mantle
AU: * Ono, S
EM: sono@jamstec.go.jp
AF: Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AU: Oganov, A R
EM: artem.oganov@mat.ethz.ch
AF: Laboratory of Crystallography Department of Materials ETH, Wolfgang-Pauli-Strasse 10, Zurich, CH-8093 Switzerland
AU: Koyama, T
EM: tkoyama@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Shimizu, H
EM: shimizu@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AB: Recently, CaIrO₃-type (post-perovskite type) high-pressure phases, such as Fe₂O₃, MgSiO₃, FeSiO₃, and Al₂O₃, have been investigated by both theoretical and experimental methods, because the CaIrO₃-type phase is likely to exist at the base of the lower mantle. As it is known that Al₂O₃ is one of major components in the solid Earth, the investigation of its physical properties is important to understand the structure and dynamics at the base of the lower mantle. Recent theoretical calculations using ab initio method indicated that CaIrO₃-type Al₂O₃ is stable at pressures higher than 100 GPa [1-3]. However, the inconsistency for predicted transition pressure among these theoretical studies was reported. Therefore, we investigated CaIrO₃-type Al₂O₃ by the high-pressure experiment. The in situ X-ray diffraction experiments were performed using a laser-heated diamond anvil cell at the synchrotron beam lines BL10XU, SPring-8 in Japan. The transition pressure from the Rh₂O₃- to CaIrO₃-type phase matched that calculated by Oganov and Ono [2]. The elastic properties of the CaIrO₃-type Al₂O₃ was also determined. The bulk modulus determined in this study was in generally agreement with those determined by previous calculations. Previous study [2] predicted that the electrical conductivity of CaIrO₃-type phase is much higher than that of perovskite phase. Therefore, this phase explains the previously puzzling electrical property of the D" layer. We will also discuss the estimated one-dimensional model of electrical conductivity in the lower mantle. [1] Caracas and Cohen, GRL 32 (2005) L06303 [2] Oganov and Ono, PNAS 102 (2005) 10828-10831 [3] Tsuchiya et al, PRB 72 (2005) 020103
DE: 3914 Electrical properties
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005