Achieving high R9 full-spectrum white LEDs through novel Na5Lu(WO4)4 Eu3+ narrow-band red phosphors

Narrow-band red phosphors offer highly effective solution to the red-spectral deficiency that has long compromised the color rendering quality of phosphor-converted white light-emitting diodes (LEDs). Herein, we report novel tungstate-based Na 5 Lu(WO 4 ) 4 :Eu 3+ (NLWO:Eu 3+ ) red phosphor synthesized by high-temperature solid-state reaction. The distinctive tetragonal framework of the Na 5 Lu(WO 4 ) 4 host provides non-centrosymmetric Lu 3+ sites that favor the hypersensitive 5 D 0 → 7 F 2 electric dipole transition of Eu 3+ , yielding an exceptionally pure red emission at 618.9 nm with a remarkable color purity of 96.22%. A systematic investigation of the concentration-dependent luminescence reveals that electric dipole-dipole interactions dominate the energy transfer and quenching behavior, with the optimal Eu 3+ content identified at x = 0.21. Importantly, the phosphor retains 78.7% of its room-temperature emission intensity at 423 K, corresponding to activation energy of 0.246 eV, indicative of robust thermal stability suitable for LED application. A full-spectrum white LED device was constructed by integrating the optimized NLWO:Eu 3+ phosphor with commercial blue and green components on 397 nm n-UV chip. The device delivers high-quality white light with a high general color rendering index (Ra = 87.5) and a markedly enhanced R9 value of 89.8, far exceeding that of conventional YAG:Ce-based white LEDs, along with comfortable correlated color temperature of 6038 K. This work presents a viable red phosphor solution for bridging the red gap in full-spectrum lighting, highlighting the potential of tungstate hosts as robust platforms for high-performance phosphor development.