Phase transition of shock loaded CaF2

Fluorite, CaF2, is a model ionic solid and prototypical structure type in condensed matter physics, undergoing pressure-induced phase transitions to a highly coordinated AX2 structure. In this study, the shock-induced phase transitions in CaF2 were investigated by plate impact experiments carried out using the single stage powder gun at Soreq NRC. Single-crystal samples in (111) and (100) orientations were shock loaded to pressures in the range of 16 to 42 GPa. The particle velocities were probed by a PDV interferometer. The wave structure evolution measured in samples of different thicknesses allowed us to extract the shock velocity in the compressed material. We observe evidence of a transition to a high-pressure phase, where the phase transition seems to be sensitive to pressure and strain-rate.