Synthesis and photoluminescence properties of LiEu(W,Mo)2O8:Bi3+ red-emitting phosphor for white-LEDs
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LiEu1−x(W2−yMoy)O8:xBi3+ 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 μm. 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 5D0–7F2 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 LiEu0.80Mo2O8:0.20Bi3+. Compared with the commercial red-emitting phosphor, Y2O2S:Eu3+, the emission intensity of LiEu0.80Mo2O8:0.20Bi3+ 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 LiEu0.80Mo2O8:0.20Bi3+ phosphor make it attractive for the application in white-light-emitting diodes (LEDs), in particular for near-UV InGaN-based white-LEDs.
KeywordsScheelite Structure Main Emission Peak Double Tungstate LMCT Band Representative Scanning Electron Microscopy Micrograph
The authors thank Dr. Jinping Huang of Shanghai Normal University for assistance with the XRD measurements. Financial support from the Natural Science Research Project of the Jiangsu Higher Education Institutions (08KJD150014), the QingLan Project of the Jiangsu Province (2008), and the Basic Research Fund of Jiangsu Teachers University of Technology is gratefully acknowledged.
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