ISSN: 1003-6326
CN: 43-1239/TG
CODEN: TNMCEW

Vol. 24    No. 1    July 2014

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White luminescence of Ho3+/Tm3+/Yb3+-codoped CaWO4 synthesized viacitrate complex route assisted by microwave irradiation
Hyun CHO1, Seok Min HWANG2, Jae Bin LEE2, Dong Hyun KA2, Tae Wan KIM2, Bo Seul LEE2, Ji Young LEE2, Jung-Il LEE2, Jeong Ho RYU2
(1. Department of Nanomechatronics Engineering, Pusan National University,
50 Cheonghak-ri, Miryang, Gyeongnam 627-706, Korea;
2. Department of Materials Science and Engineering, Korea National University of Transportation,
Chungju, Chungbuk 380-702, Korea
)
Abstract: The nanocrystalline Ho3+/Tm3+/Yb3+ co-doped CaWO4 upconversion (UC) phosphors were successfully synthesized by a modified citrate complex method using microwave irradiation. The citrate complex precursors were heat-treated at temperature ranging from 300 to 700 °C for 3 h. Crystallization of the Ho3+/Tm3+/Yb3+ co-doped CaWO4 was detected at 400 °C, and entirely completed at 600 °C. The Ho3+/Tm3+/Yb3+ co-doped CaWO4 heat-treated at 600 °C showed primarily spherical and homogeneous morphology. Under the laser excitation of 980 nm, Ho3+/Tm3+/Yb3+ co-doped CaWO4 shows the bright white upconversion (UC) emission visible to the naked eye, which is composed of a blue emission at 475 nm from Tm3+, and green and red emissions at 543 and 651 nm respectively from Ho3+. The coordinates of Ho3+/Tm3+/Yb3+ co-doped CaWO4 in the Commission International De’eclairage (CIE) chromaticity diagram could be controlled from a cool to a warm white color depending on the Tm3+ and Ho3+ concentrations. The UC luminescent properties on Tm3+ and Ho3+ concentrations and related mechanism based on laser pump power were discussed in detail.
Key words: upconversion; CaWO4; microwave irradiation; white luminescence
Superintended by The China Association for Science and Technology (CAST)
Sponsored by The Nonferrous Metals Society of China (NFSOC)
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