Color-tunable emissions via energy transfer in Bi3+ and Eu3+ doped β-LaB5O9: Sol-gel synthesis and photoluminescence

Abstract Pentaborate β-LaB5O9 was reported to be a good phosphor host for rare earth activators, like Ce3+, Eu3+, Tb3+, Sm3+ and Dy3+. Herein this work, Bi3+ was incorporated into the pentaborate structure β-LaB5O9 for the first time using the sol-gel method, and the doping upper limit is confirmed to be 17 atom% by careful analyses on the powder X-ray diffraction data. Bi3+ exhibits an intense emission band with the maximum at 440 nm and it has a slight concentration quenching at 12 atom%. Bi3+ to Eu3+ energy transfer was confirmed in β-La0.9-yBi0.1EuyB5O9 (0.025 ≤ y ≤ 0.15) phosphors according to the fast decreasing of the Bi3+ emission in both intensity and lifetime along with the increase of Eu3+ dopant concentration. Benefiting from the energy transfer, color-tunable emissions could be realized from blue to pink under UV excitation, indicated by the CIE coordinate evolution from (0.163, 0.152) to (0.318, 0.211).