Effects of flux on crystal structure and luminescent properties of nitroxides phosphors

Yellow-green-emitting SrSi₂O₂N₂:Eu²⁺ phosphors were synthesized with Sr₂SiO₄:Eu²⁺ as precursor. The effects of flux and the concentration of Eu²⁺ on the crystal structure and luminescent properties of the phosphors were investigated. Results suggested that the optimal content of flux Na₂CO₃ was 1 wt% and the optimal doping concentration of Eu²⁺ was 0.05 mol. The emission spectra showed the most intense peaks located at 535 nm which corresponded to the 4f⁶5d→4f⁷ transition of Eu²⁺. The excitation spectra showed that these phosphors could be effectively excited by near-ultraviolet and blue light, whichwas consistent with the widely applied output wavelengths of near-ultraviolet and blue-white light-emitting diode (LED) chips. When the influence of flux on the luminescent properties of SrSi₂O₂N₂:Eu²⁺ phosphor was analyzed, the X-ray diffraction (XRD) patterns indicated that the flux could help the crystallization of the phosphors. No other phases except the triclinic structure of SrSi₂O₂N₂ were formed. The thermal stability and the emission intensity of synthesized SrSi₂O₂N₂:Eu²⁺ phosphor were examined and compared with commercial YAG yellow phosphors. All results indicate that the yellow-green-emitting phosphor is a suitable candidate for the fabrication of white LEDs.