Deep red phosphors SrAl12O19:Mn4+,M (M = Li+, Na+, K+, Mg2+) for high colour rendering white LEDs

High-saturated red phosphors Mn4+-doped SrAl12O19 were prepared by solid-state reaction methods. The luminescent properties of SrAl12O19:Mn4+ were systematically investigated. The excitation spectra indicated that SrAl12O19:Mn4+ could be effectively excited by both NUV light and the blue light of LED chips. The emission spectra exhibit two sharp peaks in the deep-red region. The effects of codoping ions, M = Li+, Na+, K+, Mg2+, on the luminescent properties of SrAl12O19:Mn4+ were investigated, respectively. The results suggested that Mg2+ could significantly improve the luminescent properties of SrAl12O19:Mn4+, and the phosphor SrAl12O19:Mn4+,Mg2+ was demonstrated to be a potential candidate for high colour rendering white LEDs. CIE chromaticity diagram of different phosphors and luminescence of SrAl12O19:Mn4+,Mg2+ phosphor (a). A commercial blue LED chip coated with SrAl12O19:Mn4+,Mg2+ (b) and the luminance of SrAl12O19:Mn4+,Mg2+ excited by a 365-nm light source (c) (×: the CIE chromaticity of a blue chip LED+ YAG:Ce coated with SrAl12O19:Mn4+,Mg2+, 20 mA).