Tm3+/Yb3+共掺杂玻璃和玻璃陶瓷中蓝色 上转换发光中的能量传递过程

利用高温固相法制备了Tm³⁺/Yb³⁺共掺杂的氟氧化物玻璃和玻璃陶瓷材料,在980 nm的激光激发下,样品发射出明亮的蓝色上转换荧光。通过对玻璃和玻璃陶瓷样品的对比,发现Tm³⁺离子和Yb³⁺离子之间存在着Tm³⁺(³H₄)→Yb³⁺(²F_5/2)的反向能量传输通道,并且与晶场有较强的依赖关系。分析了在玻璃和玻璃陶瓷中蓝色上转换发光过程,随着敏化剂Yb³⁺浓度的增加,在玻璃中正向和反向能量传递的竞争作用使得Tm³⁺离子在Yb³⁺离子的最佳浓度时上转换发光最强;而在玻璃陶瓷中, Tm³⁺离子的上转换发光始终随着Yb³⁺离子的浓度增加而增强。

Mechanics of Upconversion Luminescence in Glass and Glass Ceramics Co-doped with Tm3+/Yb3+

Tm3+/Yb3+-codoped transparent oxyfluoride glass and glass ceramics were prepared by melt-quenching and subsequently heat-treatment to forming the fluoride nanocrystals embedded among the oxide glassy matrix. The advantages of these materials are that the rare earth ions are incorporated selectively in the fluoride crystal phase with lower phonon energy after heat-treatment and the material remains transparent due to much smaller size of precipitated crystals than the wavelength of visible light. Intense blue upconversion luminescence was observed under 980 nm laser excitation. X-ray diffraction (XRD) and fluorescence spectra investigation reveal that fluoride nanocrystals are distributed homogeneously among the glassy matrix for the sample doped with Tm3+/Yb3+. Tm3+ is one of the most studied rare-earth ions for blue laser operation based on upconversion. One approach to improving the luminescent efficiency of Tm3+ is to co-doped with other rare-earth ions. The choice of host materials is also an important issue when it deals with improving the efficiency of the emission process. With the increasing Yb3+ concentration, blue upconversion emissions show different variable tendency in glass and glass ceramics co-doped with Tm3+/Yb3+. In this paper, different upconversion energy transfer processes were explained and reverse energy transfer pathway from Tm3+(3H4) to Yb3+(2F5/2) was influenced by crystal lattice field in glass and glass ceramics. In glass, the competition of positive and reverse energy transfer between Tm3+ and Yb3+ ions causes maximal blue upconversion emission at optimal Yb3+ concentration. The blue upconversion emission, however, increases with the increasing Yb3+ ion in glass ceramics.