Pressure generation and investigation of the post-perovskite transformation in MgGeO3 by squeezing the Kawai-cell equipped with sintered diamond anvils

High pressure generation has been tried by using the Kawai-cell equipped with sintered diamond cubes and the synchrotron radiation at SPring-8. The maximum attainable pressure reached 90.4 GPa at 300 K based on the Anderson et al. (1989) Au scale. Simultaneously, we investigated the perovskite (Pv)–postperovskite (PPv) transformation in MgGeO3 up to ca. 74 GPa and 2200 K by means of in situ X-ray diffraction method. Transformation from Pv to PPv was observed at pressures and temperatures higher than 63 GPa and 1300 K. Both the forward and the reverse reactions were found to be fairly sluggish over the examined temperature range. We determined the phase boundary by passing through the conditions at which either Pv or PPv phase grew and that of coexistence of both the phases, which is expressed by the equation T(K) = 177 P(GPa) − 9677. Our dP/dT slope of 5.6 MPa/K for MgGeO3 is close to the minimum estimate for MgSiO3 and accordingly suggests relatively deeper D″ discontinuity and a high heat flux from the core. We emphasize that the phase boundary completely relies on the pressure scale adopted.