Synthesis, crystal structure and optical properties of BiMgVO5

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 Mossbauer 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.

Structure, luminescence, and transport properties of EuVO4

A previous investigation of EuVO4–BtVO4 binary system has indicated the existence of a solid-solution of Eu1–xBixVO4 up to x= 0.60, with a zircon-type structure. In this work we have reinvestigated the synthesis conditions, thus extending the upper limit to x= 0.74. X-Ray diffraction techniques associated with Raman and luminescence spectroscopies have led to the unambiguous identification of the structural type as a scheelite model.

H. Baussart

Papers

Contribution of Raman and Luminescence Spectroscopies to the Investigation of Phase Demixion in the System BixLn(1-x)VO4