In situx-ray diffraction study of dynamically compressedα-cristobalite using a dynamic diamond anvil cell

Abstract

In this study we present results of the dynamic compression of $\ensuremath{\alpha}$-cristobalite up to a pressure of 106 GPa with the use of the dynamic diamond anvil cell. X-ray diffraction images were recorded at different ramp compression and decompression rates to investigate in situ the high-pressure phase transitions of $\ensuremath{\alpha}$-cristobalite. Our results suggest that the pressure onset of the phase transformation of $\ensuremath{\alpha}$-cristobalite to cristobalite II, cristobalite X-I, and ultimately to seifertite ($\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{PbO}}_{2}$ type ${\mathrm{SiO}}_{2}$) is dependent on the applied compression rates and stress conditions of the experiment. Increasing compression rates in general shift the studied phase transitions to higher pressures. Furthermore, our results indicate for single crystals under hydrostatic conditions a suppression of a phase transition from cristobalite X-I to seifertite at pressures of up to 82 GPa.