Energy transfer from Tb3+ to Eu3+ in ZnLaB5O10: a candidate for near ultraviolet LED pumped phosphor

Abstract ZnLaB5O10 is a good photoluminescent host for a high concentration doping of rare earth (RE) activators and the f-f transitions in near ultraviolet range could be enhanced since RE3+ locates at an irregular cavity, in which the parity-forbidden law is partially suppressed. Two solid solutions of ZnLa1-xTbxB5O10 (0 ≤ x ≤ 1) and ZnLa0.8-yEuyTb0.2B5O10 (0.01 ≤ y ≤ 0.1) were prepared by high temperature solid state reactions and the phase purity was confirmed by powder X-ray diffraction. Under the excitation at 364 nm (the strongest f-f absorption), ZnLa1-xTbxB5O10 exhibits a monotonic increase of the bright green emission without any concentration quenching. Tb3+ to Eu3+ energy transfer in ZnLa0.8-yEuyTb0.2B5O10 was confirmed by the variation of the compositional dependent emission intensity as well as the fluorescence decay curves of Tb3+. Color-tunable emissions from green to yellow and to orange were realized in these phosphors. High thermal stability and low thermal quenching is proved by the in-situ high temperature photoluminescence spectra of ZnLa0.4Tb0.6B5O10 and ZnLa0.75Eu0.05Tb0.2B5O10.