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 °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 5D0→7F2 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.

Graphical AbstractFigure optionsDownload as PowerPoint slideHighlights
► A series of Eu3+-doped alkaline-earth tungstates were prepared by a polymeric precursor method.
► Eu3+ ions occupy low symmetry sites in the host lattice.
► The effect of the alkaline-earth ionic radius on the energy transfer from WO4 groups to Eu3+ ions was studied.
► The SrWO4:Eu3+ phosphor showed strongest luminescence intensity and better chromatic coordinates.