STRUCTURE, LUMINESCENCE AND MAGNETIC-PROPERTIES OF AGLNW(2)O(8) (LN =EU, GD, TB AND DY) COMPOUNDS

Four new compounds AgLnW(2)O(8) (Ln = Eu, Gd, Tb and Dy) are prepared by solid-state reactions. They crystallize with a scheelite-related mo noclinic symmetry. Infrared (IR) spectra show complicated absorption t ransitions in the region of 1000-400 cm(-1) that are similar to those of AgLnMo(2)O(8). Broad excitation and emission bands of the tungstate group are observed in AgGdW2O8 and AgTbW2O8 with a large Stokes shift , 12 573 and 12 387 cm(-1), respectively. Excitation and emission spec tra of AgLnW(2)O(8) (Ln = Eu, Gd and Tb) show that energy transfer fro m the tungstate to EU3+, Gd3+ and Tb3+ occurs and that Eu3+ ions occup y a single crystallographic site with the C-2 Site symmetry. (C) 1997 Elsevier Science Ltd. All rights reserved.