Photoluminescence in CaWO4:Bi3+, Eu3+ Material

Abstract

Luminescence of Bi 3+ and Bi 3- + Eu 3+ in calcium tungstate powder prepared by the solid state diffusion method has been reported. The excitation and emission bands in CaWO 4 and CaWO 4 : Bi 3+ 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% Bi 3+ ) than in the former case. The Eu 3+ emission was observed at 619 nm in CaWO 4 :Eu 3+ (1 mol%). The Eu 3+ emission intensity increased significantly (about 37 times) with the addition of a small amount of Bi 3+ . The emission band of Bi 3+ overlaps with the excitation band of Eu 3+ , resulting in a very efficient energy transfer from Bi 3+ to Eu 3+ . The energy transfer probability is strongly dependent upon the Bi 3+ concentration, with a maximum for 0.5 mol% of Bi 3+ and drastically decreases for higher concentration. The mechanism of the energy transfer from Bi 3+ to Eu 3+ has been discussed. The CaWO 4 :(Bi 3+ , Eu 3+ ) material is proposed as an efficient red phosphor.