Phase transition and sound velocity study 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 highly coordinated AX₂ structure. In this study, the shock-induced phase transitions in CaF₂ were investigated by plate impact experiments carried out with the gas guns at Soreq NRC and NRC Negev and powder gun at Soreq NRC. Single-crystal samples in (111) and (100) orientations were shock loaded to pressures between 7 GPa to 45 GPa. The particle velocities were probed by VISAR and PDV. The wave structure evolution measured in samples of different thicknesses allowed us to extract the shock velocity and sound velocity in the shock 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.