Phase transitions in Sc<SUB>2</SUB>(WO<SUB>4</SUB>)<SUB>3</SUB> under high pressure

High-pressure x-ray diffraction and Raman scattering studies on scandium tungstate [Sc2(WO4)3] show that it transforms to a monoclinic phase at -0.6± 0.3 GPa. The high-pressure phase has P21/a symmetry and is related to the initial orthorhombic phase through cell doubling along the c axis. The compound undergoes another phase transition at -1.6 GPa, accompanied by a volume reduction of -8%. At -6.5 GPa, the diffraction pattern and Raman spectra of Sc2(WO4)3 indicate the emergence of a disordered crystalline state which evolves into an amorphous phase beyond -14 GPa. The structural changes are found to be reversible up to -1.6 GPa. However, transformation to the amorphous state is found to be irreversible, though our results suggest some structural relaxation on release of pressure