NIR emission spectral engineering in NaSc(Si,Ge)2O6: Cr3+ solid-solution phosphors via crystal field regulation

A series of NIR-emitting NaSc(Si 2- x Ge x )O 6 : Cr 3+ phosphors have been synthesized by a solid-state reaction. NaSc(Si 2- x Ge x )O 6 is found to retain the same monoclinic crystal structure and form a solid-solution within the entire composition range. When excited by 470 nm blue light, the phosphors emit broadband and tunable emission with a peak maximum shifting from 850 nm to 910 nm, depending on the Si/Ge ratio. Fluorescence decay curves and temperature dependent photoluminescence were also discussed. With increasing Ge 4+ content, the red-shift behaviors can be ascribed to the weakened crystal field splitting from lattice expansion, and the emission intensities first increased, then decreased, and finally increased to the maximum at x = 0.2. As discussed, optimal NaSc(Si 1.8 Ge 0.2 )O 6 : Cr 3+ phosphor have potential applications as a source for NIR lighting. • Solid-solution NIR-emitting phosphor NaSc(Si 2- x Ge x )O 6 : Cr 3+ was synthesized. • Precise peak tuning in 850–910 nm range with emission enhancement of 1.5 times is realized. • Emission red-shift behaviors can be ascribed to weaken crystal field splitting from lattice expansion.