Effect of Composition and Impurities on the Phosphorescence of Green-Emitting Alkaline Earth Aluminate Phosphor

Recent improvements to SrAl 2 O 4 :Eu 2+ , Dy 3+ phosphors have enabled the use of luminescent hosts with a stable crystal structure and high physical and chemical stability, thus overcoming the bottleneck in the applicability of ZnS:Cu phosphors. However, enhancement of afterglow lifetime and brightness in SrAl 2 O 4 :Eu 2+ , Dy 3+ phosphors remains a challenging task. Here, we have improved the afterglow characteristics in terms of persistence time and brightness by a systematic investigation of the composition of Eu-doped alkaline earth aluminate SrAl 2 O 4 :Eu 2+ , Dy 3+ crystals. We found that a Dy 3+ /Eu 2+ ratio of ~2.4 and ~0.935 mol Eu 2+ (per mol of SrAl 2 O 4 ) gave the brightest and longest emissions (11% and 9% increase for each). Doping with Si 4+ also resulted in a slight increase in brightness up to ~15%. Doping with alkali metal or alkaline earth metal significantly enhanced the phosphorescence intensity. In particular, doping with 0.005 mol Li + (per mol of SrAl 2 O 4 ) alone boosted the phosphorescence intensity to 239% of the initial value, as compared to that observed for the non-doped crystal, while doping with 0.01 mol Mg 2+ and 0.005 mol Li + (per 1 mol SrAl 2 O 4 ) boosted the phosphorescence intensity up to 313% of the initial value. The results of this investigation are expected to act as a guideline for the synthesis of bright and long persistent phosphors, and facilitate the development of persistent phosphors with afterglow characteristics superior to those of conventional phosphors.