Optical spectrum adjustment of yellow-green Sr1.99SiO4−3x/2Nx:0.01Eu2+ phosphor powders for near ultraviolet-visible light application

Si3N4 doped yellow-green Sr1.99SiO4−3x/2Nx:0.01Eu2+ phosphors were synthesized through the solid-state reaction technique in reduced air condition. Under the excitation of near ultraviolet and visible light, the emission spectra showed a broad band peaking at 540 nm, which originated from the 4f65d1 → 4f7 transitions of Eu2+ ions. There is a significant improvement in the luminescence efficiency with the addition of Si3N4. Under the excitation of 370 nm light, the Sr1.99SiO4−3x/2Nx:0.01Eu2+ displayed distinct shoulders ranging from 450 nm to 550 nm. It was attributed to Eu2+ ions occupying the lattice sites of Sr2+ and forming two different luminescence center of Eu(I) and Eu(II). Meanwhile, the fluorescent decay lifetime of Sr2SiO4:Eu2+ phosphor was prolonged remarkably by addition of Si3N4. CIE chromaticity coordinates showed that the emission spectra gradually shifted from green to yellow region, with the increase of N concentration.