Influence of pressure-induced structural change in Al2O3–SiO2 glasses on the sound velocity and Poisson's ratio under pressure

Abstract

In this study, we investigated pressure-induced changes in the structure and elastic property of xAl₂O₃–(100−x)SiO₂ glasses (x=29, 36, 43, 50, 60 mol.%; referred to as xAS) by in situ high-pressure pair distribution function measurement and sound velocity measurement. The 29AS and 60AS glasses are regarded as the Si-rich/Al-rich end-member compositions, and the 36AS, 43AS, and 50AS glasses consist of the two end-member phases in nano-scale. The 29AS glass shows gradual changes in the intermediate-range order up to 9.3 GPa, similarly to SiO₂ glass, while the 60AS glass exhibits a rapid structural change at 7.4–8.4 GPa, similarly to CaAl₂O₄ glass. This rapid structural change causes a kink in sound velocity–pressure trend near 8 GPa, as also observed CaAl₂O₄ glass. In contrast, the Si-rich end-member 29AS glass does not exhibit the velocity kink.The Poisson's ratios of the five AS glasses and the SiO₂ glass start to converge above ~11 GPa, finally reaching a constant value of ~0.32 at the pressure condition of ~20 GPa. This result indicates that both of the Si-rich and Al-rich end-members have a similar structure above ~20 GPa.