High-pressure generation in the Kawai-type multianvil apparatus equipped with tungsten-carbide anvils and sintered-diamond anvils, and X-ray observation on CaSnO₃ and (Mg,Fe)SiO₃

We extended the attainable pressure of the Kawai-type multianvil apparatus to 71.3 GPa and 120.3 GPa at room temperature by equipping it with tungsten carbide (WC)and sintered diamond (SD)cubic anvils, respectively. In the experiments with WC anvils, pressure decreased largely, ΔP ∼−20 GPa, on heating from room temperature to 1500 K. In the experiments with SD anvils, pressure also dropped to 105 GPa from 120 GPa at 1673 K. In order to generate higher pressure and temperatures, therefore, innovation of SD material in both quality and size are essential, together with improvements of cell assembly. Besides pressure generation, we conducted in situ energy-dispersive X-ray diffraction observations on CaSnO₃ and (Mg,Fe)SiO₃ in the experiments with WC and SD anvils, respectively. We observed the growth of new peaks, which can be assigned to the post-perovskite phase, transformed from a starting material of CaSnO₃ perovskite at 48.4 GPa and 1500 K, although they are not clearly identified. In contrast, we could not observe the post-perovskite phase of (Mg,Fe)SiO₃ in the present P–T conditions generated by experiments with SD anvils.