[S-MP26] Physics and Chemistry of Minerals

[SMP26-P08] Phase transitions and pressure calibration points

*Shigeaki Ono¹ (1.Japan Agency for Marine-Earth Science and Technology)

Keywords:Phase transformation, High-pressure experiment

Some phase transitions have been used as pressure calibration in high-pressure experiments, because reliable characterization of the pressure and temperature environment is of essential importance when we apply laboratory data to the study of the Earth’s interior. In order to know reliable pressure environment, we can use the synchrotron X-ray source for the high-pressure studies. The in-situ pressure measurement has been accessible by the synchrotron X-ray technique. In the case of conventional laboratory experiments, this technique cannot be used and the conventional pressure calibration is of great interest to understand the Earth’s interior. We have investigated several high-pressure phase transitions used as the pressure calibration points. Precise determinations of phase boundaries of SiO₂ [1], Fe₂SiO₄ [2], CaGeO₃ [3], ZnS [4], ZnSe [5], GaAs [6], GaP [7], Zr [8], and Bi [9] were performed by the multi-anvil press or the diamond anvil cell apparatuses combined with the synchrotron X-ray diffraction technique. Most transition pressures determined our studies were in general agreement with those reported by previous studies. However, some significant discrepancies for the pressure values or the slopes, dP/dT, of transitions between our and previous studies were confirmed. These discrepancies are due to the significant kinetics effect at the phase transition, because an apparent hysteresis was confirmed at relatively low temperature conditions. This indicates that the phase transitions accompanied with the significant hysteresis are not suitable for the pressure calibration.



[1] S. Ono et al. (2017) In situ determination of the phase boundary between coesite and stishovite in SiO₂, Phys. Earth Planet. Inter., 264, 1-6.

[2] S. Ono et al. (2013) In situ observation of a phase transition in Fe₂SiO₄ at high pressure and high temperature, Phys. Chem. Minerals, 40, 811-816.

[3] S. Ono et al. (2011) In situ observation of a garnet-perovskite transition in CaGeO₃, Phys. Chem. Minerals, 38, 735-740.

[4] S. Ono, T. Kikegawa, (2018) Determination of the phase boundary of ZnS, Phase Transition, 91, 9-14.

[5] S. Ono (2020) Phase transition in ZnSe at high pressures and high temperatures, J. Phys. Chem. Solids, 141, 109409.

[6] S. Ono, T. Kikegawa (2018) Phase transformation of GaAs at high pressures and temperatures, J. Phys. Chem. Solids, 113, 1-4.

[7] S. Ono, T. Kikegawa (2017) Determination of the phase boundary of GaP using in situ high-pressure and high-temperature X-ray diffraction, High Press. Res., 37, 28-35.

[8] S. Ono, T. Kikegawa (2015) Determination of the phase boundary of the omega to beta transition in Zr using in situ high-pressure and high-temperature X-ray diffraction, J. Solid State Chem., 225, 110-113.

[9] S. Ono (2020) High-pressure phase transition of bismuth, High Press. Res., 38, 414-421.