Journal of Materials Science, Vol.45, No.1, 118-123, 2010
Synthesis and photoluminescence properties of LiEu(W,Mo)(2)O-8:Bi3+ red-emitting phosphor for white-LEDs
LiEu1-x (W2-y Mo (y) )O-8:xBi(3+) series red-emitting phosphors were synthesized by solid state reaction. The structure, morphology, and photoluminescent properties of phosphors were studied by X-ray powder diffraction, scanning electron microscopy, and photoluminescence spectrum, respectively. X-ray powder diffraction analysis showed that the as-obtained phosphors belong to the scheelite structure. The average particle size of the investigated phosphor was about 8 mu m. The excitation spectrum exhibits a charge-transfer broad band along with some sharp peaks from the typical 4f-4f transitions of Eu3+. Under excitation of UV, near-UV, or blue light, these phosphors showed strong red emission at 615 nm due to D-5(0)-F-7(2) transition of Eu3+. The incorporation of Mo6+ into LiEuW2O8:Bi3+ could induce red-shift of the charge-transfer broad band and a remarkable increase of photoluminescence. The highest red-emission intensity was observed with LiEu0.80Mo2O8:0.20Bi(3+). Compared with the commercial red-emitting phosphor, Y2O2S:Eu3+, the emission intensity of LiEu0.80Mo2O8:0.20Bi(3+) phosphor is much stronger than that of Y2O2S:Eu3+ and its chromaticity coordinates are closer to the standard values than that of the commercial phosphor. The optical properties of LiEu0.80Mo2O8:0.20Bi(3+) phosphor make it attractive for the application in white-light-emitting diodes (LEDs), in particular for near-UV InGaN-based white-LEDs.