High performance Sr4Al14O25:Mn4+ phosphor: structure calculation and optical properties
Abstract
The deficiency of high optical performance oxide red phosphors limits the application and development in the field of warm WLEDs. In this work a Sr4Al14O25:Mn4+ (SAO:Mn4+) series of oxide red phosphors efficiently excited by blue chips were prepared. The theoretical calculations, structure and luminescence properties were systematically studied. The results of theoretical calculation and experiments both demonstrate that Mg2+ can improve the PL intensity and thermal quenching properties of SAO:Mn4+ phosphors. Mn4+ emits red light only in the Sr4Al14O25 structure, but not in the SrAl2O4 structure. The high crystallinity pure phase of Sr4Al14O25 is obtained at 1250 °C and the impure phase of SrAl2O4 appears at 1300 °C. The optimum Mg2+ doping concentration is Mg2+/Mn4+ of 1 : 1 and maximum PL intensity appears at 0.5 mol% Mn4+. The phosphor exhibits excellent water resistance and acceptable thermal stability. Encapsulating as-prepared SAO:Mn4+,Mg2+ and commercial YAG:Ce3+ yellow phosphors, the WLED device operating with blue chips yields a low correlated color temperature of 4737 K, high color rendering index of 81.7 and luminous efficiency of 153.61 lm W−1. The above results show that the as-prepared SAO:Mn4+,Mg2+ phosphor is a potential candidate for warm WLEDs.