Structure, Luminescence, and Transport Properties of EuVO_4

Metastable scheelite EuVO_4 was stabilized by a high temperature and pressure method, which was transformed into a stable zircon phase by annealing treatment in air. Scheelite EuVO_4 gave strong emissions with a dominant peak at 617 nm associated with the ^(5)D_0-^(7)F_2 transition of Eu^(3+). ^(151)Eu Mössbauer spectra indicated that the isomer shift for the metastable scheelite phase was ca. 0.5 mm/s lower than that for the zircon phase, which was ascribed to a reduced covalency in the Eu-O bond originated via a charge transfer from oxygen to Eu3+ in scheelite lattice by producing an enhanced shielding of 4f electrons on the s orbital as well as a decrease in s electron density around Eu^(3+) nucleus. Impedance spectra for the zircon phase clearly demonstrated an ionic hopping in the bulk with a conductivity of ca. 1.0×10^(–3) S cm^(–1) at 500°C. EuVO_4 is proved to be both a potential phosphor and a potential ionic conductor