High-pressure Raman study of Al 2(WO 4) 3

A high-pressure Raman scattering study of the tungstate Al ₂(WO ₄) ₃ is presented. This study showed the onset of two reversible phase transitions at 0.28±0.07 and 2.8±0.1 GPa. The pressure evolution of Raman bands provides strong evidences that both the transitions involve rotations/tilts of nearly rigid tungstate tetrahedra and that the structure of the stable phase in the 0.28-2.8 GPa range may be the same as the structure of the ambient pressure, low-temperature monoclinic ( C_{2 h}⁵) ferroelastic phase of Al ₂(WO ₄) ₃.