Thermally Driven Eu2+ Site-Selective Occupation Enables Narrow-Band Green Emission in an Oxolithoaluminate Phosphor for Backlight Display Applications

Developing narrow-band green phosphors via selective site occupancy engineering remains challenging for wide-color-gamut displays. While Eu 2+ -doped UCr 4 C 4 -type nitride and oxynitride lithoaluminates exhibit narrow-band emission and high thermal stability, their emission spectra are confined to red–orange region due to the pronounced nephelauxetic effect of N 3− ions. To address this limitation, we design a nitrogen-free oxolithoaluminate phosphor, Sr 5/6 Li 17/6- x Al 7/6- x Zn 2 x O 4 :Eu 2+ (SLAZO:Eu 2+ ), synthesized via a stepwise solid-state reaction with Zn 2+ doping ensuring phase stabilization. Crucially, elevating the sintering temperature from 780°C to 870°C confined Eu 2+ occupancy from dispersed Sr1–Sr5 sites (distorted [SrO 8 ] cubes) to larger Sr2a/b and Sr3a/b sites, thereby transforming emission from dual-band yellow–green to a singular narrow-band green peak at 528 nm. The optimized phosphor exhibits a narrow full-width-at-half-maximum (FWHM) of 51 nm (1784 cm −1 ) under 400 nm excitation. It has an internal/external quantum yield of 41.6%/20.1% and maintains 54.2% of its emission intensity at 150°C relative to 25°C. A white LED device fabricated with SLAZO:Eu 2 + , K 2 TiF 6 :Mn 4 + , and a 450 nm blue chip achieves a color gamut covering 97.4% of the National Television System Committee standard. This study demonstrates thermally-driven site-selective occupation as an effective strategy for emission tuning and validates SLAZO:Eu 2+ as a promising narrow-band green emitter for next-generation displays.