Synthesis and photoluminescence properties of (Y,Gd)Al_3(BO_3)_4:Tb~(3+) under VUV excitation

摘要

Single phase of Y_xGd_(0.5-x)Tb_(0.5)Al_3(BO_3)_4 (0 ≤ x ≤ 0.5) was prepared by the thermal decomposition of the corresponding nitrates. The main broad band in 120-178 nm and some other bands in 178—288 nm were observed in the excitation spectrum of Gd_(0.5)Tb_(0.5)Al_3(BO_3)_4 monitored at 541 nm. The former could be assigned to overlapped absorptions among the f → d transition of Gd~(3+), charge transfer bands of O~(2-) → Ln~(3+) (Ln = Tb, Gd) and BO_3 groups. The latter was ascribed to 4f~8 → 4f~75d transitions of Tb~(3+). Under 147 nm excitation the maximum emission peak was observed at about 541 nm in the emission spectrum of Gd_(0.5)Tb_(0.5)Al_3(BO_3)_4, which was due to the ~5D_4 → ~7F_5 transition of Tb~(3+); when substituting Gd~(3+) with appropriate Y~(3+), the emission intensity of the ~5D_4 → ~7F_5 transition of Tb~(3+) increased, and the optimum emission was obtained at x = 0.1 in Y_xGd_(0.5-x)Tb_(0.5)Al_3(BO_3)_4. This could be due to that electronic transitions occurred from O~(2-):~2p_6 to Y~(3+):~4p_6 (4d + 5s) and the absorbed energy transferred to Tb~(3+) finally, as observed in the excitation spectrum of Y_(0.1)Gd_(0.4)Tb_(0.5)Al_3(BO_3)_4. The decay time of the ~5D_4 → ~7F_5 transition of Tb~(3+) decreased after Y~(3+) replacing Gd~(3+), which could be attributed to increasing defect impurities in Y_(0.1)[Gd_(0.4)Tb_(0.5)Al_3(BO_3)_4 under 147 nm excitation.