PRESSURE-INDUCED PHASE-TRANSITION IN YVO4EU3+ - A LUMINESCENCE STUDY AT HIGH-PRESSURE

The pressure dependence of the emission from the Eu3+ ion in YVO4:Eu3+ has been investigated to 14 GPa, using a diamond anvil cell. Abrupt changes in the luminescence spectra of Eu3+ ion at 7 GPa, which, after removal of pressure, did not reverse, indicated that a pressure-induced, irreversible phase transition had occurred. The luminescence spectra from the high pressure phase showed the characteristics of a distorted D2d symmetry, which can be explained by considering only the first coordination sphere oxygens about the Eu3+ ion in an S4 symmetry site. The change in the energy separation between the 5D0 and 7F0 levels from the low pressure phase to the high pressure phase is discussed. A decrease of the effective charge on the oxygen atoms in the high pressure phase occurs and is correlated with a charge transfer mechanism that arises because of the phase transition.