Investigation of the phase stability of LuVO₄ at high pressure using powder x-ray diffraction measurements and lattice dynamical calculations

Abstract

High pressure angle dispersive x-ray diffraction measurements are carried out on LuVO₄ in a diamond anvil cell up to 33 GPa at the Elettra synchrotron radiation source. The measurements show that LuVO4 undergoes a zircon to scheelite structure phase transition with a volume change of about 11% at about 8 GPa. A second transition to a monoclinic fergusonite structure occurs above 16 GPa. The data are also recorded while releasing the pressure, and indicate that the scheelite phase is metastable under ambient conditions. The equations of state and changes in internal structural parameters are reported for various phases of LuVO₄. Lattice dynamical calculations based on a transferable interatomic potential were also performed and the results support the stability of the scheelite structure at high pressures. The calculated structure, equation of state and bulk modulus for all the phases are in fair agreement with the experimental observations.