Structure and luminescence properties of some new AgLnW(2)O(8) compounds

Three new compounds, AgLnW(2)O(8) (Ln(3+)=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 KLnW(2)O(8). Broad excitation and emission bands of the tungstate group with a large Stokes shift (12573 cm(-1)) are observed in AgGdW2O8. Excitation and emission spectra of AgLnW(2)O(8) (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 C-2 site symmetry.