Generation of pressures to approximately 60 GPa in Kawai-type apparatus and stability of MnGeO (sub 3) perovskite at high pressure and high temperature

To obtain higher pressures in a Kawai-type apparatus, we explored and tested high-pressure cell assemblies suitable for experiments using sintered diamond (SD) anvils. As a result, we succeeded in generating pressures exceeding 55 GPa at temperatures of approximately 1000 degrees C in a Kawai-type apparatus (SPEED Mk-II) at SPring-8. Using the optimized cell assembly, we examined the stability field of MnGeO (sub 3) perovskite, an analog of MgSiO (sub 3) perovskite, which was recently found to transform to a new high-pressure form under the P-T conditions near the core-mantle boundary. From our in situ X-ray observations, MnGeO (sub 3) perovskite was found to be stable at pressures up to 56-57 GPa at temperatures of 800-1050 degrees C.