A LUMINESCENCE STUDY OF EUVO4 AT HIGH-PRESSURE

The pressure dependence of the luminescence from the F-7(1,2) <-- 5D0 transitions of Eu3+ ion in EuVO4 has been investigated to 5.6 GPA using a diamond anvil cell. At ambient pressure two of the F-7(1) <-- 5D0 transitions are degenerate in the zircon-type phase of EuVO4; however this degeneracy is removed with the application of pressure (greater-than-or-equal-to 0.8 GPA). Abrupt changes in the luminescence spectrum from the Eu3+ ion were observed at 4.5 GPA, which remained even after removal of pressure, indicating that a pressure-induced, irreversible phase transition had occurred. The Eu3+ ion luminescence spectrum from the high-pressure, scheelite-type phase of EuVO4 exhibited the characteristics of a distorted D2d symmetry instead of the S4 site symmetry determined from the results of X-ray diffraction analysis. The effect of pressure on the energy levels of the Eu3+ ion in EuVO4 is discussed.