In situ observation of a phase transition in Fe2SiO4 at high pressure and high temperature

We used an in situ measurement method to investigate the phase transition of Fe2SiO4 polymorphs under high pressures and temperatures. A multi-anvil high-pressure apparatus combined with synchrotron X-ray radiation was used. The stability of each polymorph was identified by observing the X-ray diffraction data from the sample. In most experiments, the diffraction patterns were collected 10-30 min after reaching the desired pressure and temperature conditions. The transition boundary between the olivine and spinel phase at T = 1,000-1,500 K and P = 2-8 GPa was determined to occur at P (GPa) = 0.5 + 0.0034 x T (K). The transition pressure determined in this study was in general agreement with that observed in previous high-pressure experiments. However, the slope of the transition, dP/dT, determined in our study was significantly higher than that estimated by the previous study combined with the in situ X-ray method.