Opposite effect of Li+ codoping on the upconversion emissions of Er3+-doped TiO2 powders |
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Authors: | B. S. Cao Z. Q. Feng Y. Y. He H. Li B. Dong |
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Affiliation: | (1) School of Science, Dalian Nationalities University, Dalian, 116600, China;(2) Department of Physics, University of Duisburg-Essen, Duisburg, 47057, Germany;(3) College of Life Science, Dalian Nationalities University, Dalian, 116600, China; |
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Abstract: | The Er3+-Li+ codoped TiO2 powders have been prepared by the non-aqueous sol–gel method. The green and red upconversion emissions centered at about 526, 550 and 663 nm were observed by the 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+, respectively. Li+ codoping has opposite effect on the upconversion emissions intensities for Er3+-doped TiO2 at sintering temperatures of 1,073 and 1,273 K. At 1,073 K, the Er3+-doped TiO2 phase transition from anatase to rutile was accelerated with increasing Li+ codoping concentration, leading to the increase of crystal field symmetry of Er3+, thus the upconversion emissions intensities decreased. At 1,273 K, Li+ codoping had no effect on the phase structure of Er3+-doped TiO2 and only increased the Er–O bond length, it indicated that the upconversion emissions intensities greatly enhanced because of the decrease of crystal field symmetry of Er3+. |
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