Synthesis and Luminescence of BaWO4:Ln3+ (Ln = Eu, Tb, and Dy) Powders

BaWO4:Ln(3+) powders were synthesized by a solid-state reaction method. The BaWO4:Ln(3+) samples were characterized by x-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), and luminescence spectroscopy. The XRD patterns reveal that the BaWO4:Ln(3+) samples present pure tetragonal scheelite structure. The SEM observations demonstrate that the BaWO4:Ln(3+) powders are irregular particles with size in the range of micrometers. The excitation spectra of the BaWO4:Ln(3+) samples show the broad absorption band originating from charge transfer between oxygen ligands and the central tungstate ions inside WO (4) (2-) groups in the metal tungstate. The emission spectra of the BaWO4:Ln(3+) samples display the bands associated to the anion molecular complex (WO (4) (2-) ) and the f-f transitions of Ln(3+). According to the emission spectra and the chromaticity coordinates (Commission internationale de l',clairage, CIE), one can see that the BaWO4:Eu3+, BaWO4:Tb3+, and BaWO4:Dy3+ samples show emission in the red, green, and yellow region, respectively. The results show that the luminescence color can be altered by changing the Ln(3+) doping in BaWO4 material.