Ba 2+ Co-doping Enhances Phase Purity and Enables Narrow-Band Green Emission in Sr 5/6 Li 17/6 Al 7/6 O 4 :Eu 2+ Phosphor for Backlight Display Applications

Abstract

Alkaline earth lithoaluminates with the UCr4C4-type structure have demonstrated considerable potential in achieving narrow-band emissions from Eu 2+ . However, obtaining single-phase powder samples with green-emitting remains challenging. In this study, we address this issue by co-doping Ba 2+ into the novel UCr4C4-type system Sr5/6-xBaxLi17/6Al7/6O4:Eu 2+ , which significantly enhances phase purity and structural homogeneity. This approach not only reduces the emission bandwidth from 66 nm (2241 cm -1 ) to 51 nm (1830 cm -1 ) but also induces a blue shift to 529 nm, fine-tuning the emission into the desired deep green region. Through detailed mechanistic studies-including low-temperature spectroscopy and luminescence decay analysis-we identify the presence of multiple Eu 2+ emission centers associated with distinct Sr 2+ sites. Ba 2+ doping is shown to promote dominant Eu 2+ emission in the green spectral region, thereby facilitating spectral narrowing.The optimized phosphor achieves a high absorption efficiency of 64.6% and an external quantum yield of 22.2%. When integrated into a white LED prototype, it enables a color gamut covering 97.6% of the NTSC (National Television System Committee) standard, outperforming a commercial β-SiAlON:Eu 2+ -based device. This study provides an effective cationic codoping strategy for designing high-performance narrow-band oxide phosphors and highlights a promising candidate for nextgeneration display technologies.