Vol. 38, Issue 1, pp. 39-47 (2008)

Abstract

A series of luminescent materials consisting of Tb_2–xEu_x (WO₄)₃ entrapped in silica xerogel were successfully prepared. The parameter x in the formula changed from 0.4 to 2. Spectroscopic properties such as absorption and luminescence of optically active ions were studied at room temperature. Owing to the energy transfer from the WO₄^2- groups (ligand–metal charge transfer, (LMCT)) the lanthanide ions show their characteristic emissions in Tb_2–xEu_x(WO₄)₃ entrapped in silica xerogel, i.e., ⁵D₀ → ⁷F_J (J = 0, 1, 2, 3, 4) transition for Eu³⁺ ion and ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transition for Tb³⁺ ion. The energy transfer is effective for the mixed tungstate salt Tb_1.35Eu_0.65(WO₄)₃ entrapped in silica xerogel. The Eu(III) emission intensity in the materials under study increases with an increase in the annealing temperature from 600 to 900 °C. This is due to the removal of the effective O –H quenchers from the coordination sphere of the Eu(III) ion.