Shock-induced phase transition in GaP

Abstract

Shock compression and adiabatic release experiment have been performed on single crystal GaP oriented parallel to the (221) plane up to about 140 GPa using a two‐stage light‐gas gun. Inclined mirror experiments reveal the three‐wave structure, yielding the Hugoniot elastic limit and apparent phase transition pressure to be 7.2 and 22.9 GPa, respectively. The relative volume discontinuity due to the phase transition is almost the same as those of Si, Ge and Sn. The release adiabat originated from the shock‐induced high‐pressure phase is determined by means of the buffer technique. The volume at 0 GPa on the release adiabat is smaller by about 20% than that of the initial low pressure phase, indicatig that the high pressure phase is almost retained within a submicrosecond time scale after pressure is released. A double‐shocked state is measured at about 140 GPa. Gruneisen parameter of the high pressure phase estimated from this result is about four times greater than that of the normal pressure phase. Resistivity measurements under shock loading indicate that the shock‐induced high‐pressure phase is metallic.