A novel red-emitting Na5W3O9F5:Eu3+phosphor with high color purity for blue-based WLEDs

Red phosphor plays a key role in improving the lighting and display quality of phosphor-converted white light -emitting diodes (pc-WLEDs). Meanwhile, developing new luminescent matrix materials can positively contribute to the acquisition of ideal and efficient phosphors. In this work, we propose a novel red-emitting Na5W3O9F5: Eu3+ (NWOF:Eu3+) phosphor. The phase composition, morphology, electronic structure and photoluminescence properties of the NWOF:Eu3+ phosphor were systematically investigated. The EXAFS results prove that the Eu3+ dopants occupy the Na2 and Na3 sites in the NWOF host. Under 466 nm blue light excitation, NWOF:xEu3+ (0.05 <= x <= 0.25) phosphors display a dominant red emission at 607 nm and achieves a high color purity (97.44%) due to the dominant electric dipole transition (5D0 -> 7F2) of Eu3+ ions. Impressively, this red-emitting NWOF:0.25Eu3+ phosphor exhibits relatively superior thermal stability (450 K, >50%) and excellent chroma-ticity stability (2.32 x 10-4 <= Delta E <= 6.23 x 10-3) from 298 K to 498 K. The activation energy for thermal quenching effect is determined to be 0.22 eV. Moreover, the pc-WLED was fabricated by coupling a 460 nm blue chip with the as-synthesized NWOF:0.25Eu3+ red phosphor and commercial YAG:Ce3+ phosphor. The optical parameters of the as-fabricated pc-WLED are also measured, and the CIE coordinates remain almost constant as the drive current increases from 20 mA to 120 mA. These results indicate that the NWOF:0.25Eu3+ red phosphors should be a suitable candidate as a red component for the preparation of pc-WLEDs.