Structure, Luminescence, and Transport Properties of EuVO₄

Metastable scheelite EuVO₄ was stabilized by a high temperature and pressure method, which was transformed into a stable zircon phase by annealing treatment in air. Scheelite EuVO₄ gave strong emissions with a dominant peak at 617 nm associated with the ⁵D_0-⁷F₂ transition of Eu³⁺. ¹⁵¹Eu 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 Eu³⁺ 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. EuVO₄ is proved to be both a potential phosphor and a potential ionic conductor.