Synthesis and photoluminescence properties of Eu³⁺ doped Sr₅Nb₄O₁₅ red-emitting phosphors for white LEDs

In this paper, a novel red-emitting material based on Eu3+ ion activated Sr5Nb4O15 was synthesized via a solid-state reaction method. The XRD patterns indicated that the sample, heated at 1300 degrees C for 6 h, could obtain pure phase with high crystallinity. The phosphors displayed irregular shapes with an averages diameter of approximately 0.66 mu m. Excited upon 393 nm, the phosphors exhibited bright red emission peak at 613 nm, being assigned to the electric dipole D-5(0)-F-7(2) transition of Eu3+ ions. In addition, the effect of Eu3+ doping concentration on the emission intensity was investigated in detail. The optimal doping concentration for the best PL performance was experimentally determined to be 15 mol%, beyond which the concentration quenching behavior occurred. The critical distance was calculated to be about 16 angstrom, revealing that the process of energy transfer between Eu3+ ions in Sr5Nb4O15 host was dominated by multipolar interaction. The chromaticity coordinates of the Sr4.85Nb4O15: 0.15Eu(3+) phosphor were calculated to be (0.6354, 0.3642), closing to the standard NTSC values (0.67, 0.33). Thus, the Sr5Nb4O15: Eu3+ red phosphors could be potential candidates for the application in solid-state White LEDs, combined with near ultraviolet chip.