Er3＋-Yb3＋共掺杂（NaxLi1-x）YF4上转换发光特性研究

Upconversion Luminescence Properties of Era＋-Yb3＋ Codoped （NaxLi1-x）YF4

采用溶胶-凝胶法制备了摩尔分数为2％Er3＋20％Yb3＋共掺杂的（NaxLi1-x）YF4纳米晶粉末。随着Na＋摩尔分数由x=0增加到100％，Er3＋-Yb3＋共掺杂（NaxLi1-x）YR纳米晶相结构主要发生了由四方相LiYF4到单斜相LiNaY2F8再到六方相NaYF4的转变。在976nm半导体激光器激发下，Er3＋-Yb3＋共掺杂（NaxLi1-x）YF4获得了分别对应于Er3＋的4G11/2→4I15/2、2H9／2→4I15／2、2H11/2／4S3/2→4I15/2和4F9／2→4I15/2跃迁的紫色、蓝色、绿色和红色上转换发光，且上转换发光强度随着Na＋含量增加而逐渐增强。Er3＋-Yb3＋共掺杂（NaxLi1-x）YF4纳米晶上转换发光强度的变化与其相结构紧密相关。

2% Er3＋-20% Yb3＋ （mole fraction） codoped （NaxLi1-x）YF4 upconversion nanocrystal powders are prepared by sol-gel method. The phase transition from tetragonal LiYF4 phase to monocline LiNaY2Fs phase and hexagonal NaYF4 phase in Er3＋-Yb3＋ codoped （Nax Li1-x ）YF4 is investigated with increasing of Na＋ concentration x from 0 to 1.0. Violet, blue, green and red upconversion emissions corresponding to the Er3＋ transitions of G11/2→4I15/2、2H9/2→4I15/2、2H11/2/4S3/2→4I15/2 and 4F9/2→4I15/2 are observed from the Er3＋ -Yb3＋ codoped （ Nax Li1-x ） YF4 under 976 nm laser diode excitation, respectively. The upconversion emissions intensities increase with increasing of Na＋ concentration. It is found that the upconversion luminescence properties of Er3＋-Yb3＋ codoped （NaxLi1-x）YF4 are closely related to their phase structures.