Tunable wide rectangular red fluorescence spectrum of Mn⁴⁺-doped Li₃LaMgTiO₆

The Li₃LaMgTiO₆ phosphor doped with Mn⁴⁺ was synthesized using the solid phase gradient temperature technique. The micro-structure and spectral properties were characterized through XRD and fluorescence spectrum analysis. The experimental results demonstrate that it exhibits a typical layered structure, and the gradient temperature technique can effectively modify and distort the crystal cell structure from tetrahedral to cubic system. This transformation alters the required octahedral structure for Mn⁴⁺, resulting in the splitting of ²A levels into ²E_g and ²T₁, thereby enlarging the energy level spacing. Consequently, due to reduced non-radiative transition probability of ²T₁ → ²E_g, a blue shift phenomenon will be formed in the fluorescence peak. By utilizing a 358 nm LED as a pump source, we observed this phenomenon in fluorescence peaks from 711 to 680 nm. Furthermore, by adjusting the gradient temperature zone, it is possible to obtain a full-width half-maximum (FWHM) rectangular fluorescence spectrum up to 100 nm with excellent homogeneity of light intensity, which holds great promise for applications in opto-electronics and crop fields.