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.