Enhancement of photoluminescence properties and modification of crystal structures of Si3N4 doping Li2Sr0.995SiO4:0.005Eu2+ phosphors

• Si3N4 modified Li2Sr0.995SiO4:0.005Eu2+ phosphors were prepared.
• The luminescence intensity of Li2Sr0.995SiO4:Eu2+ was enhanced by doping Si3N4.
• The fluorescence decay times and thermal stability were enhanced by doping Si3N4.

Si3N4 modified Li2Sr0.995SiO4:0.005Eu2+ (Li2Sr0.995SiO4−3x/2Nx:0.005Eu2+) phosphors were synthesized with the conventional solid-state reaction in the reduced atmosphere. The crystal structure and vibrational modes were analyzed by X-ray diffraction, Raman scattering spectroscopy and Rietveld crystal structure refinement. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra showed that Li2Sr0.995SiO4−3x/2Nx:0.005Eu2+ powder exhibited a broad yellow emission band centered at 560 nm under the excitation of 460 nm visible light, due to the 4f65d1 → 4f7 transition of Eu2+. The partial nitridation of Li2Sr0.995SiO4−3x/2Nx:0.005Eu2+ (x = 0.01) phosphors led to a large enhancement in the luminescence intensity, as much as 190%. At the same time, the fluorescence decay behavior curves further showed that the photoluminescence efficiencies of Li2Sr0.995SiO4−3x/2Nx:0.005Eu2+ phosphors were enhanced by addition of Si3N4. The temperature quenching characteristics confirmed that the oxynitride based Li2Sr0.995SiO4−3x/2Nx:0.005Eu2+ showed slightly higher stability. It is implied that Li2Sr0.995SiO4−3x/2Nx:0.005Eu2+ phosphors had a possible potential application on white LEDs to match blue light chips.

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