Pressure-Induced Structural and Electronic Transition in Sr2ZnWO6 Double Perovskite

High-pressure structural and electrical properties of Sr2ZnWO6 double perovskite were investigated using in situ angle-dispersive synchrotron X-ray diffraction (XRD), Raman, and alternating current (AC) impedance spectroscopy. A structural transition from monoclinic (P2(1)/n) to triclinic (P (1) over bar) phase around 9 GPa was observed due to the pressure-induced distortion of (W, Zn)O-6 octahedron. In situ high-pressure Raman spectroscopy showed the increasing interaction among O-W-O in WO6 octahedron with pressure and a transition pressure consistent with the XRD results. From the AC impedance spectroscopy measurements, the resistivity increased steeply by similar to 1 order of magnitude around 11 GPa, indicating an electronic transition accompanying the symmetry change. The increase in the interaction among O-W-O enhances the attraction of O2- electrons toward W6+, thus increasing the covalence, which in turn lowers the charge transfer energy between O2- and W6+ and induces the resistivity increase under high pressure.