Structure and luminescence properties of some new AgLnW₂O₈ compounds

Abstract

Three new compounds, AgLnW₂O₈ (Ln³⁺=Eu, Gd or Tb), have been prepared by a solid-state reaction and crystallize with a scheelite-related monoclinic symmetry. Their IR spectra show absorption transitions in the region 1000–400 cm^-1 similar to KLnW₂O₈ . Broad excitation and emission bands of the tungstate group with a large Stokes shift (12 573 cm^-1) are observed in AgGdW₂O₈ . Excitation and emission spectra of AgLnW₂O₈ (Ln=Eu or Tb) show that energy transfer from tungstate to Eu and Tb occurs and that Eu³⁺ ions occupy a unique crystallographic site with C₂ site symmetry.

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