Luminescence investigation of R3+-doped alkaline earth tungstates prepared by a soft chemistry method

Abstract

Highly luminescent rare earth (R3+) doped alkaline-earth tungstates MWO4:R3+ (M2+: Ca, Sr and Ba, R3+: Eu, Tb, Gd) were prepared with a room temperature coprecipitation method. The phosphors were characterized by X-ray powder diffraction (XPD), thermal analysis (TG), infrared absorption spectroscopy (FTIR) and UV excited photoluminescence. The as-prepared MWO4:R3+ particles belong to the tetragonal scheelite phase, and are well crystallized and are of the average size of 16–48nm. The excitation and emission spectra of the materials were recorded at 300 and 77K temperatures. The luminescent materials exhibit intense red (Eu3+) and green (Tb3+) colors under UV excitation. The excitation spectra of the Eu3+ doped materials show broad bands arising from the ligand-to-metal charge transfer transitions (O2−→WVI and O2−→Eu3+) as well as narrow bands from 4f–4f intraconfigurational transitions of Eu3+. 4f–4f emission data of the Eu3+ and Tb3+ in the MWO4 host matrices as well as the values of emission quantum efficiencies of the 5D0 level and the 4f–4f experimental intensity parameters of Eu3+ ion are presented and discussed.