In situ determination of the spinel-post-spinel transition in Fe3O4 at high pressure and temperature by synchrotron X-ray diffraction

Abstract

The position of the spinel-post-spinel phase transition in Fe3O4 has been determined in pressuretemperature space by in situ measurements using a multi-anvil press combined with white synchrotron radiation. Pressure measurement using the equation of state for MgO permitted pressure changes to be monitored at high temperature. The phase boundary was determined by the first appearance of diffraction peaks of the high-pressure polymorph (h-Fe3O4) during pressure increase and the disappearance of these peaks on pressure decrease along several isotherms. We intersected the phase boundary over the temperature interval of 700-1400 °C. The boundary is linear and nearly isobaric, with a slightly positive slope.