P-V-T equation of state of periclase from synchrotron radiation measurements

Abstract

The volume of periclase (MgO) has been measured by monochromatic X-ray diffraction in a laser-heated diamond anvil cell up to a pressure of 53 GPa and a temperature of 2500 K. The X-ray source was synchrotron radiation at the European Synchrotron Radiation Facility (Grenoble, France). In addition to laser heating, the use of argon as a pressure transmitting medium provided quasi-hydrostatic conditions in the cell assembly. In order to take thermal pressure effect into account, pressure was measured using an internal pressure calibrant (platinum). By analysis of the experimental P-V-T data set the following parameters were obtained: at ambient temperature, Kl0 = 3.94 ± 0.2 when K0 is fixed to 161 GPa (with a Birch-Murnaghan equation of state); under high temperature, α(P = 0,T) = (3.0 + 0.0012T) x 10-5 K-1; (∂KT/∂T)P = -0.022(3) GPa K-1. The quasi-harmonic Debye model appears to describe correctly the temperature dependence of the volume at high pressure within experimental errors, with the following parameters: θD0 = 800 K, γ0 = 1.45 (Grüneisen parameter under ambient conditions), and q = 0.8 ± 0.5. Copyright 2000 by the American Geophysical Union.