Synthesis and photoluminescence properties of (Y,Gd)Al3(BO3)4:Tb3+ under VUV excitation

Single phase of YxGd0.5-xTb0.5Al3(BO3)(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 Gd0.5Tb0.5Al3(BO3)(4) monitored at 541 nm. The former could be assigned to overlapped absorptions among the f -> d transition of Gd3+, charge transfer bands of O2- -> Ln(3+) (Ln = Tb, Gd) and BO3 groups. The latter was ascribed to 4f(8) -> 4f(7)5d transitions of Tb3+. Under 147 nm excitation the maximum emission peak was observed at about 541 nm in the emission spectrum of Gd0.5Tb0.5Al3(BO3)(4), which was due to the D-5(4) -> F-7(5) transition of Tb3+; when substituting Gd3+ with appropriate Y3+, the emission intensity of the D-5(4) -> F-7(5) transition of Tb3+ increased, and the optimum emission was obtained at x = 0.1 in YxGd0.5-xTb0.5Al3(BO3)(4). This could be due to that electronic transitions occurred from O2-:(2)p(6) to Y3+:(4)p(6) (4d + 5s) and the absorbed energy transferred to Tb3+ finally, as observed in the excitation spectrum of Y0.1Gd0.4Tb0.5Al3(BO3)(4). The decay time of the D-5(4) -> F-7(5) transition of Tb3+ decreased after Y3+ replacing Gd3+, which could be attributed to increasing defect impurities in Y0.1Gd0.4Tb0.5Al3(BO3)(4) under 147 nm excitation. (c) 2006 Elsevier B.V. All rights reserved.