Photoluminescence properties and energy transfer of Ba2Lu(BO3)2Cl : Eu2+/Eu3+,Tb3+ phosphors

Abstract

Novel green-emitting Ba2Lu(BO3)2Cl : Eu2+/Eu3+,Tb3+ phosphors were synthesized via a solid-state reaction. It was found that Eu3+ could be detected when the so-called Ba2Lu(BO3)2Cl : Eu2+,Tb3+ were prepared in a reducing atmosphere. Through efficient energy transfer processes between Eu2+, Tb3+ and Eu3+, the emission intensities of Tb3+ and Eu3+ were significantly enhanced due to the spectra overlap. The lifetime of Eu2+ in Ba1.97−yLu(BO3)2Cl : 0.03Eu2+/Eu3+, yTb3+ phosphors was 1.32 µs in the absence of Tb3+ (y = 0) and then it decreased to 0.62 µs (y = 0.3). The proposed schematic diagram for energy transfer processes indicated that an effective resonance type energy transfer occurred between Eu2+ and Tb3+ (ηT = 53%); however, the energy transfer between Tb3+ and Eu3+ was attributed to the charge transfer from Tb3+ to Eu3+. Accordingly, Tb3+ ions exhibited characteristic green emission peaks corresponding to the strong excitation band of Eu2+ ions (300–450 nm), matching well with the dominant emission band of near ultraviolet (n-UV, 350–420 nm) light-emitting diodes. The present green-emitting Ba2Lu(BO3)2Cl : Eu2+/Eu3+,Tb3+ phosphors exhibit potential as a kind of phosphor-converted materials for n-UV white light-emitting diodes.