An in situ X ray diffraction study of the α-β transformation kinetics of Mg₂SiO₄

This is the first report of the direct measurement of α-β transformation kinetics in Mg₂SiO₄, a major constituent in the Earth's mantle, through in situ X ray diffraction experiments at high pressure. The experiments were conducted using the sintered diamond cubic-anvil apparatus with synchrotron radiation (MAX 80). Although the present work is still preliminary, the kinetic data were analyzed using a nucleation and growth model. The growth rate of β-phase is determined to be 3.3 (1.6∼4.9) × 10-¹⁰ m/s at 13.0 GPa and 900°C, 7.1 (3.4∼10) × 10-¹⁰ m/s at 14.1 GPa and 885°C, and 1.5 (0.7∼2.3) × 10^-9 m/s at 14.9 GPa and 875°C.