Synthesis and Luminescence Properties of Tb3+-Doped K2BaW2O8 Phosphors

Abstract

Green phosphors K 2 BaW 2 O 8 :Tb 3+ (1.0 mol%) were synthesized by solid state reaction method. Differential thermal analysis was applied to trace the reaction processes. Three endothermic values of 95, 706, and 1055 o C correspond to the loss of absorbed water, the release of carbon dioxide, and the beginning of the melting point, respectively. The phase purity of the powders was examined using powder X-ray diffraction(XRD). Two strong excitation bands in the wavelength region of 200-310 nm were found to be due to the WO 4 2− exciton transition and the 4f-5d transition of Tb 3+ in K 2 BaW 2 O 8. The excitation spectrum presents several lines in the range of 310-380 nm; these are assigned to the 4f-4f transitions of the Tb 3+ ion. The strong emission line at around 550 nm, due to the 5 D 4 → 7 F 5 transition, is observed together with weak lines of the 5 D 4 → 7 F J (J = 3, 4, and 6) transitions. A broad emission band peaking at 530 nm is observed at 10 K, while it disappears at room temperature. The decay times of Tb 3+ 5 D 4 → 7 F 5 emission are estimated to be 4.8 and 1.4 ms, respectively, at 10 and 295 K; those of the WO 4 2− exciton emissions are 22 and 0.92 µs at 10 and 200 K, respectively.