Synthesis and photoluminescent behavior of Eu3+-doped alkaline-earth tungstates

Eu3+-doped alkaline-earth tungstates MWO4 (M=Ca2+, Sr2+, Ba2+) were prepared by a polymeric precursor method based on the Pechini process. The polymeric precursors were calcined at 700 degrees C for 2 h in order to obtain well-crystallized powders and then characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and photoluminescence spectroscopy (PL). All prepared samples showed a pure crystalline phase with scheelite-type structure confirmed by XRD. It was noted that the charge-transfer band shifted from 260 to 283 nm when calcium is replaced by strontium. However, this band was not observed for Eu3+-doped barium tungstate. Upon excitation at 260 nm, the emission spectra are dominated by the red D-5(0)-> F-7(2) transition at 618 nm. By analyzing of the emission lines, it was inferred that Eu3+ ions occupy low symmetry sites in the host lattice. It was also found that Eu3+-doped SrWO4 displays better chromaticity coordinates and greater luminescence intensity than the other samples. (C) 2012 Elsevier Ltd. All rights reserved.