Spectroscopic properties and intense red-light emission of (Ca, Eu,M)WO4 (M = Mg, Zn, Li)

The red-emitting phosphors of (Ca, Eu, M)WO4 (M = Mg, Zn, Li) were prepared through solid-state reactions, and their spectroscopic properties were studied. After the addition of a small amount of Mg2+, Zn2+ or Li+ in (Ca, Eu)WO4, the red-light emission intensity of Eu3+ increases obviously. In the luminescence spectra of the phosphors, the predominant transition emission is D-5(0) -> F-7(2) (616 nm), whereas the other emissions are very weak. The excitation spectra are composed of interweaved ligand-to-metal charge-transfer bands (CTB) of W6+-O-2(-) and Eu3+-O-2(-), and a few 4f excitation transitions of Eu3+. Among the 4f excitation transitions of Eu3+, there are three strong excitation lines corresponding to F-7(0) -> L-5(6), F-7(0) -> D-5(2) and F-7(0) -> D-5(1), transitions whose relative excitation intensity ratio is seriously affected when Li+ doped in the host. The new phosphors may be applied as red-emitting phosphors for white light emitting diodes. (C) 2007 Elsevier B.V. All rights reserved.