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

Author： Xia Zhiguo Zhuang Jiaqing Liu Haikun Liao Libing

ISSN： 0022-3727

Source： Journal of Physics D: Applied Physics, Vol.45, Iss.1, 2012-01, pp. : 15302-15308

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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 Ba_1.97−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⁺ (η_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)₂Cl : Eu²⁺/Eu³⁺,Tb³⁺ phosphors exhibit potential as a kind of phosphor-converted materials for n-UV white light-emitting diodes.