Transformation in intermediate-range structure of vitreous silica under high pressure andtemperature

Abstract

The pressure dependence of the structure factor for vitreous silica was measured up to 8.3 GPa at500 °C by means of an in situ x-ray diffraction method. The position of the first sharp diffraction peak(FSDP) moved to a higher momentum transfer as the pressure increased. It moved rapidlybetween 3.3 and 5.8 GPa, and then the slope of the FSDP position as a function of pressuredecreased. The pressure dependence of the position is the same as that for a sample heated to500 °C after room-temperature compression. On decompression at500 °C, the position of the FSDP showed hysteresis. The pressure dependence of the FSDPposition suggests that the permanent densification of vitreous silica is realized due topreservation of the intermediate-range structure stabilized at high pressure andtemperature.