采用溶胶凝胶法制备摩尔分数为x(Er3+)=0.1% Er3+,x(Li+)=0-2% Li+共掺杂TiO2粉末。800 ℃烧结Li+共掺杂促进掺Er3+:TiO2由锐钛矿向金红石相转变,900 ℃和1000 ℃烧结Er3+-Li+:TiO2均为单一金红石相。976 nm激光激发下Er3+-Li+:TiO2均获得中心波长为526 nm和550 nm的绿色和663 nm的红色上转换发光,绿色和红色上转换发光均为双光子吸收过程。随着Li+共掺杂浓度逐渐增大,800 ℃烧结Er3+-Li+:TiO2上转换发光强度逐渐减小,900 ℃烧结发光强度先增加后减小,1000 ℃烧结发光强度显著增强。不同烧结温度下Li+共掺杂对Er3+所处晶体场对称性的改变导致上转换发光强度随Li+共掺杂浓度增加出现不同的变化规律。结果表明,Li+共掺杂可有效提高Er3+:TiO2上转换发光强度。

The TiO2 powders codoped by mole fraction x(Er3+)=0.1% Er3+ and x(Li+)=0-2% Li+ are prepared by the sol-gel method. The TiO2 phase transition from anatase to rutile is accelerated by Li+ codoping at the sintering temperature of 800 ℃,while only rutile phase existes at 900 ℃ and 1000 ℃. The green and red upconversion emissions centering at about 526,550 and 663 nm are detected by using a 976 nm semiconductor laser diode excitation. The two-photon absorption upconversion process is responsible for the green and red upconversion emissions. With the increase of the Li+ codoping concentration,the upconversion emissions intensities of Er3+-Li+:TiO2 sintered at 800 ℃ decreases,and that increases firstly and then decreases at 900 ℃,while the emission intensity increases significantly at 1000 ℃. The changes of crystal-field symmetry of Er3+ caused by Li+ codoping at different sintering temperature result in the variation of upconversion emission intensities of Er3+-Li+:TiO2. It is found that Li+ codoping can efficiently enhance the upconversion emission intensities of Er3+:TiO2.