Structural Evolution and Effect of the Neighboring Cation on the Photoluminescence of Sr(LiAl3)(1-x)(SiMg3)(x)N-4:Eu2+ Phosphors

In this study, a series of Sr(LiAl₃)_1−x(SiMg₃)_xN₄:Eu²⁺ (SLA‐SSM) phosphors were synthesized by a solid‐solution process. The emission peak maxima of SLA‐SSM range from 615 nm to 680 nm, which indicates structural differences in these materials. ⁷Li solid‐state NMR spectroscopy was utilized to distinguish between the Li(1)N₄ and Li(2)N₄ tetrahedra in SLA‐SSM. Differences in the coordination environments of the two Sr sites were found which explain the unexpected luminescent properties. Three discernible morphologies were detected by scanning electron microscopy. Temperature‐dependent photoluminescence and decay times were used to understand the diverse environments of europium ions in the two strontium sites Sr1 and Sr2, which also support the NMR analysis. Moreover, X‐ray absorption near‐edge structure studies reveal that the Eu²⁺ concentration in SLA‐SSM is much higher than that in in SrLiAl₃N₄:Eu²⁺ and SrSiMg₃N₄:Eu²⁺ phosphors. Finally, an overall mechanism was proposed to explain the how the change in photoluminescence is controlled by the size of the coordinated cation.