THERMAL EXPANSIVITY OF MGSIO3 PEROVSKITE UNDER HIGH-PRESSURES UP TO 20 GPA

Volume measurement of MgSiO3 perovskite was made in the temperature ra nge from 25 to 500 degrees C as a function of pressure up to 20 GPa by in situ x-ray diffraction, using a DIA apparatus combined with synchr otron radiation. The measured thermal expansivity ranges from 1.8 to 2 .510(-5) /K and decreases only slightly with pressure. Our present re sults are in good agreement with the previous lower pressure (up to 11 GPa) data of Wang er al. [1994] and the higher pressure (36 GPa) data of Funamori and Yagi [1993], but contrast with the results using diam ond anvil cell by Mao et al.[1991], particularly in a low pressure ran ge.