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 pre pared by a solid-state reaction and crystallize with a scheelite-relat ed monoclinic symmetry. Their IR spectra show absorption transitions i n 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 (1 2573 cm(-1)) are observed in AgGdW2O8. Excitation and emission spectra of AgLnW(2)O(8) (Ln=Eu or Tb) show that energy transfer from tungstat e to Eu and Tb occurs and that Eu3+ ions occupy a unique crystallograp hic site with C-2 site symmetry.