Studies on material properties of the subducted slab and lower mantle

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We have designed and installed the large-volume high P-T apparatus for in situ X-ray observation, SPEED-Mk.II in the white-X-ray beam line BL04B1 at the third generation synchrotron radiation facility, SPring-8. By using sintered diamond anvils, we have extended the pressure range generated by multi-anvil apparatus from 40 to 63 GPa. SPEED-Mk.II is equipped with the oscillation system, which enables us to obtain high-quality diffraction pattern against grain growth. We have demonstrated the usefulness of this system by determining the phase boundary of B1-B2 transition in NaCl.We have also obtained the following results in earth sciences. 1)We have shown presence of oxygen defect in Mg-perovskite due to the substitution of Al_2O_3 by means of NMR spectroscopy. 2)We have determined pressure dependence of shear and bulk moduli of MgSiO_3 perovskite, Mg_2SiO_4 ringwoodite and Mg_2SiO_4 wadsleyite by resonance technique. 3)We have determined the melting relation in peridotite at pressures up to 33 GPa. 4)We have studied the phase relation of iron, showing absence of beba-phase that is recently reported by several studies. 5)We have determined the equation of state of CaSiO_3 perovskite up to 40 GPa. 6)We have determined the stability relations of MgAl_2O_4 calcium ferrite. 7)We have studied the phase relations in NaAlSiO_4, determining the stability field of the calcium ferrite phase. 8)We have measured electrical conductivities of (Mg, Fe)_2SiO_4 perovskite and ilmenite up to 40 GPa.