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

Novel green-emitting Ba2Lu(BO3)(2)Cl: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)(2)Cl: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)(2)Cl:0.03Eu(2+)/Eu3+,yTb(3+) phosphors was 1.32 mu s in the absence of Tb3+ (y = 0) and then it decreased to 0.62 mu s (y = 0.3). The proposed schematic diagram for energy transfer processes indicated that an effective resonance type energy transfer occurred between Eu2+ and Tb3+ (eta(T) = 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)(2)Cl:Eu2+/Eu3+,Tb3+ phosphors exhibit potential as a kind of phosphor-converted materials for n-UV white light-emitting diodes.