Thermally Driven Eu 2+ Site‐Selective Occupation Enables Narrow‐Band Green Emission in an Oxolithoaluminate Phosphor for Backlight Display Applications

ABSTRACT 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.