High-pressure x-ray diffraction and Raman scattering studies on scandium tungstate $\left[{\mathrm{Sc}}_2{\left(\mathrm{W}{\mathrm{O}}_4\right)}_3\right]$ show that it transforms to a monoclinic phase at $\sim 0.6\pm 0.3\mathrm{GPa}$. The high-pressure phase has $P{2}_1∕a$ symmetry and is related to the initial orthorhombic phase through cell doubling along the $c$ axis. The compound undergoes another phase transition at $\sim 1.6\mathrm{GPa}$, accompanied by a volume reduction of $\sim 8\%$. At $\sim 6.5\mathrm{GPa}$, the diffraction pattern and Raman spectra of ${\mathrm{Sc}}_2{\left(\mathrm{W}{\mathrm{O}}_4\right)}_3$ indicate the emergence of a disordered crystalline state which evolves into an amorphous phase beyond $\sim 14\mathrm{GPa}$. The structural changes are found to be reversible up to $\sim 1.6\mathrm{GPa}$. However, transformation to the amorphous state is found to be irreversible, though our results suggest some structural relaxation on release of pressure.

• Received 28 March 2005

DOI:https://doi.org/10.1103/PhysRevB.72.064106