Sound velocity measurements of epsilon-FeOOH up to 24 GPa

摘要

The sound velocity and density of epsilon-FeOOH have been simultaneously measured up to 24 GPa at room temperature using an ultrasonic pulse-echo-overlap method and a Kawai-type multi-anvil apparatus at BL04B1 in SPring-8. In the experimental pressure range, the velocity of both the P- and S-waves of epsilon-FeOOH was similar to 15 lower than that of an isostructural phase delta-AlOOH. The pressure dependence of the determined adiabatic bulk modulus (K-S) increased in the higher pressure range beyond 17 GPa, whereas that of the axial ratios a/c and b/c did not transition from negative to positive. A similar change of pressure dependence of K-S was observed in delta-AlOOH, which is followed by a transition of proton distribution state to disordered, but the axial ratios of epsilon-FeOOH indicate that the transition would not occur up to 24 GPa.