Photoluminescence in CaWO4:Bi3+, Eu3+ Material

Abstract

Luminescence of Bi3+ and Bi3+ + Eu3+ in calcium tungstate powder prepared by the solid state diffusion method has been reported. The excitation and emission bands in CaWO4 and CaWO4:Bi3+ coincide and appear at 256 and 430.5 nm, respectively. The 430.5 nm emission band is ten times stronger in the latter case (for 1 mol% Bi3+) than in the former case. The Eu3+ emission was observed at 619 nm in CaWO4:Eu3+ (1 mol%). The Eu3+ emission intensity increased significantly (about 37 times) with the addition of a small amount of Bi3+. The emission band of Bi3+ overlaps with the excitation band of Eu3+, resulting in a very efficient energy transfer from Bi3+ to Eu3+. The energy transfer probability is strongly dependent upon the Bi3+ concentration, with a maximum for 0.5 mol% of Bi3+ and drastically decreases for higher concentration. The mechanism of the energy transfer from Bi3+ to Eu3+ has been discussed. The CaWO4:(Bi3+, Eu3+) material is proposed as an efficient red phosphor.