High-pressure Raman scattering study on zircon- to scheelite-type structural phase transitions of RCrO4

High-pressure Raman scattering experiments were performed on the zircon-type RCrO4 (R=Nd, Dy) compounds with the space group I4(1)/amd by using diamond anvil cell techniques at room temperature. These two compounds exhibit similar Raman behaviors. Pressure-induced structural phase transitions were observed at the onset of 1.3 and 4.1 GPa for R=Nd and Dy, respectively. Moreover, pressure-released Raman spectra indicate that the structural transitions are irreversible. The high-pressure new phases were convincingly confirmed to be the scheelite structure in I4(1)/a symmetry based on the same Raman vibrations between the pressure-released DyCrO4 and the scheelite-type DyCrO4 synthesized at 6 GPa and 450 degrees C. In addition, we also calculated the bulk moduli according to Errandonea's method as well as the mode Gruneisen parameters of RCrO4. (C) 2008 American Institute of Physics.