Measuring the electrical resistivity of vanadium across the shock-induced phase transformation

Vanadium undergoes a solid-solid phase transformation from a body-centered cubic (bcc) to a rhombohedral (rh) structure under high pressure, significantly affecting its physical and mechanical properties, including strength and transport properties. In this paper, we investigated the electrical resistivity of vanadium subjected to shock compression. Using a four-probe technique in conjunction with one- and two-stage light gas guns, in situ measurements of the electrical resistivity of vanadium foil were performed at pressures reaching $\ensuremath{\sim}50$ GPa and temperatures nearing 750 K. The findings reveal a distinct discontinuity in electrical resistivity at shock pressures between 32 and 36 GPa. These results align with prior shock compression experiments involving sound velocity measurements, suggesting that the bcc-to-rh phase transformation in vanadium happens at 32--36 GPa under shock loading---substantially lower than the transition pressure reported under hydrostatic conditions (62--69 GPa at room temperature). In this paper, we confirm that the bcc-to-rh phase transformation in vanadium, driven by shear softening, is strongly dependent on hydrostatic stress, where the nonhydrostatic and shock compression could significantly facilitate the transformation.