Quasi-hydrostatic compression of ferropericlases up to 60 GPa and 1100 K

Abstract

The compression data of both (Mg0.83,Fe0.17)O and (Mg0.75,Fe0.25)O ferropericlases have been measured up to 60 GPa at the three temperatures of 300, 700, and 1100 K, using synchrotron powder X-ray diffraction experiments with a Kawai-type multi-anvil apparatus and sintered diamond anvils. Temperature-pressure-volume equations of state of both ferropericlases with high spin Fe2+ ions have been developed using these measured compression data below ∼50 GPa, based on the Mie-Grüneisen-Debye type model, with the 300 K Birch-Murnaghan equation. We have found that the calculated pressures based on these EOS models reproduce the measured pressures of the two ferropericlase below ∼50 GPa very accurately over the three temperatures of 300, 700, and 1100 K. We have further found that for each ferropericlase, and for each temperature of 300, 700, and 1100 K, a clear volume reduction from the compression curve with high spin Fe2+ starts at ∼50 GPa and the volume reduction increases with increasing pressure, due to a progressive high spin to low spin transition in the Fe2+ ions.