Raman Investigation of BaWO₄-II Phase under Hydrostatic Pressures up to 14.8GPa

The BaWO₄-II phase is synthesized at 5.0GPa and 610°C with a cubic-anvil apparatus and identified by XRD. Raman scattering measurement is carried out to investigate the phase behaviour of a pure BaWO₄-II phase (space group P2₁/n, Z=8) under hydrostatic pressures up to 14.8GPa at ambient temperature. In each spectrum recorded for this phase, 27 Raman modes are observed, and all bands shift toward higher wavenumber with a pressure dependence ranging from 3.8 to 0.2cm^-1/GPa. No pressure-driven phase transition occurs in the entire pressure range in this study. Our results indicate that the previously reported high pressure phase of BaWO₄ at pressure above about 10GPa and room temperature (Errandonea et al. Phys. Rev. B 73(2006)224103) is not the BaWO₄-II phase.