Pressure-induced phase transitions of β-type pyrochlore CsTaWO6

The beta-type pyrochlore CsTaWO6 was studied by synchrotron X-ray diffraction (XRD) and Raman scattering methods up to pressures of 43 GPa using a diamond anvil cell (DAC). With increasing pressure, the cubic pyrochlore in space group of Fd-(3) over barm transforms to an orthorhombic structure (space group: Pnma) at 5.9 GPa and then to a monoclinic structure (space group: P2(1/c)) at similar to 18 GPa. The structural evolution in CsTaWO6 is a continuous process and experimental results suggest that the initial cubic phase has a tetragonal distortion at ambient conditions. Both XRD and Raman measurements indicate that the pressure-induced phase transitions in CsTaWO6 are reversible. These results may provide a structural explanation of previous experimental resistivity measurement results for the isostructural superconductor K(Cs) Os2O6 at high pressure conditions.