Photoluminescence properties, excellent thermal stability and energy transfer in Ce3+ and Tb3+ co-doped Sr3Gd2(BO3)4 phosphors

Sr3Gd2(BO3)4: Ce3+, Sr3Gd2(BO3)4: Tb3+ and Sr3Gd2(BO3)4: Ce3+, Tb3+ phosphors were synthesized through conventional high temperature solid state reaction method. Phase purity, crystal structure, photoluminescence properties, and lifetime of the samples were analyzed in detailed. Sr3Gd2(BO3)4: Ce3+ showed a bright blue broad emission band, which was attributed to 4f → 5d transitions of the Ce3+ ions, and it exhibited two broad excitation ranged from 200 nm to 400 nm. For all Sr3Gd2(BO3)4: Tb3+ samples, under ultraviolet excitation bands of 240 nm, four emissions peaked at 490 nm, 544 nm, 585 nm and 623 nm appeared, due to the 5D4 → 7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions. For the Sr3Gd2(BO3)4: Ce3+, Tb3+ phosphors, the lifetime of the samples were analyzed, which showed the presence of energy transfer between the Ce3+ and Tb3+. The energy transfer efficiency from Ce3+ ions to Tb3+ ions reached 98.37%. When the temperature reached 443 K, the luminescence intensity reached 88% of the initial value. Finally, a white LED was fabricated by using a 365 nm near ultraviolet LED chip combined with BaMgAl10O17: Eu2+ (blue), Sr3Gd0.91(BO3)4: 0.09Ce3+, 1.0 Tb3+ (green), and CaAlSiN3: Eu2+ (red) phosphors. The color coordinates was (0.40, 0.42); correlated color temperature was 3721 K; color rendering index was 91.1. The results showed that the Sr3Gd2(BO3)4: Ce3+, Tb3+ green phosphors were suitable for white LEDs.