Raman and Optical Absorption Studies of the Pressure Induced Zircon to Scheelite Structure Transformation in TbVO sub 4 and DyVO sub 4

The pressure-induced phase transition in terbium vanadate and dysprosium vanadate from the zircon-type structure D sup 19 sub 4h to the scheelite-type structure C sup 6 sub 4h has been studied at room temperature by high-pressure Raman spectroscopy in a diamond anvil cell. The pressure dependencies of the Raman active modes are presented to 18 GPa in TbVO sub 4 and 10 GPa in DyVO sub 4. From this data the transition pressures are found to be 6.6 += 0.6 GPa for TbVO sub 4 and 6.5 += 0.3 GPa for DyVO sub 4.