Mechanism of upconversion luminescence enhancement in Yb3+/Er3+ co-doped Y2O3 through Li+ incorporation

Xiongfeng Yang; Min Liu; Jiandang Liu; Yuanhua Xia; Weiwei Ji; Zhiang Li; Jifang Chen; Liu Liu; Luyuan Hao; Bingbing Dong; Simeon Agathopoulos; Xin Xu

doi:10.1039/c9cp06137a

Mechanism of upconversion luminescence enhancement in Yb³⁺/Er³⁺ co-doped Y₂O₃ through Li⁺ incorporation

Phys Chem Chem Phys. 2020 Feb 7;22(5):2819-2826. doi: 10.1039/c9cp06137a. Epub 2020 Jan 21.

Authors

Xiongfeng Yang¹, Min Liu², Jiandang Liu³, Yuanhua Xia⁴, Weiwei Ji¹, Zhiang Li¹, Jifang Chen¹, Liu Liu¹, Luyuan Hao¹, Bingbing Dong¹, Simeon Agathopoulos⁵, Xin Xu¹

Affiliations

¹ CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China. xuxin@ustc.edu.cn.
² School of Materials Science & Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai, 201418, P. R. China. liumin1106@ustc.edu.cn.
³ State Key Laboratory of Particle Detection and Electronic, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China.
⁴ Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999, China.
⁵ Department of Materials Science and Engineering, University of Ioannina, GR-451 10 Ioannina, Greece.

PMID: 31960860
DOI: 10.1039/c9cp06137a

Abstract

Li⁺ doping is a well-known, simple, yet efficient strategy to optimize the properties of upconverting materials. Nonetheless, the position of Li⁺ in the lattice and the mechanism of upconversion enhancement are still controversial, especially in Yb³⁺/Er³⁺ co-doped Y₂O₃. This paper presents a comprehensive investigation of the above issues (i.e. the position occupied by Li⁺ in the lattice and the mechanism of luminescence enhancement, in terms of decreased defects) by studying (Y_0.78-XYb_0.20Er_0.02Li_X)₂O₃ powders. Neutron powder diffraction was employed for the first time in the literature to show that Li⁺ ions are accommodated in Y sites of YO₆ octahedra, confirmed also by the content of oxygen defects, which was increased with the increase of Li⁺ concentration. FT-IR showed that there was a small change in the amount and the type of the surface-absorbed groups with the increase in the Li⁺ content, thus not supporting the prevailing conclusion that the quenching groups are decreased by doping Li⁺. Positron annihilation lifetime (PLAS) experiments showed that the total defect concentration and the large defect clusters, which are considered as quenching centers, are decreased with increasing Li⁺-content, resulting in the enhancement of the emission intensity in Yb³⁺/Er³⁺ co-doped Y₂O₃.