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

Abstract

A series of NIR-emitting NaSc(Si2-xGex)O6: Cr3+ phosphors have been synthesized by a solid-state reaction. NaSc(Si2-xGex)O6 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 Ge4+ 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(Si1.8Ge0.2)O6: Cr3+ phosphor have potential applications as a source for NIR lighting.