An applicability of ceramic materials as pressure media for ultra high pressure experiment has been examined. Compressibility and the generated pressure for three kinds of ceramics, namely, semi fired-silica, -alumina and -magnesia, as well as raw and fired pyrophillite were compared to each other. The compressibility was measured at room temperature and at pressure level than 1.5GPa, with the use of uni-axial piston cylinder type apparatus. While ultra-high pressure generation was conducted by use of a hexahedral anvil type high-pressure apparatus.
High pressure experiment at elevated temperatures was carried out using alumina and fired pyrophilite pressure media. The highest pressure of about 5.5GPa was attained at room temperature in the case of alumina, magnesia and fired pyrophillite, while in the case of silica and unfired pyrophillite, generation of a pressure high than 5.5GPa was difficult. The compressibility of ceramic pressure media was considerably affected by its porosity. The compressibility of ceramic media increased with the order of alumina, magnesia and silica. In the case of pyrophillite, the efficiency for pressure generation decreased at high temperature and higher pressure level, while alumina ceramics did not show any appreciable decrease of the efficiency. When alumina ceramics was used as a pressure media, higher electric power supply was required for heating compared with fired pyrophillite. In conclusion, ceramic material is considered to be applicable as a pressure medium for ultra-high pressure generation.
