Effects of replacement of AlO+ for SiN+ on the structure and optical properties of Sr2Si5N8:Eu2+phosphors

The influence of the replacement of SiN+ by AlO+ on crystal structure and luminescence properties is reported in a series of Sr2Si5−xAlxN8−xOx:0.02Eu2+ phosphors. Changes of refined lattice parameters of the powder X-ray diffraction data suggest that preferential occupation occurred in the evolution of crystal structure: only NII atoms which are connected with two Si atoms can be substituted by O atoms. It is evidenced that Al and O have adverse influence on the emission bands, which just keep the emission peak position around 620 nm. Time-resolved photoluminescence analysis has been employed to describe the energy transfer in Sr2Si5−xAlxN8−xOx:Eu2+ samples. The energy transfer effect depends partly on lattice vibration, i.e. phonon energy. Furthermore, the improved photoluminescence intensity and thermal quenching behavior after substituting of AlO+ for SiN+ allowed Sr2Si5−xAlxN8−xOx:0.02Eu2+ a promising candidate as a red phosphor in the white LED applications when x≤0.4.