Luminescent Properties, Afterglow Behavior and Thermoluminescence Characteristics of (Eu, Dy) Doped Sr3Al2O6 Phosphors

(Eu, Dy) doped Sr3Al2O6 phosphors with high brightness and long afterglow were achieved by a high-temperature solid state reaction. Luminescence measurements indicate that the phosphor Sr3Al2O6:Eu prepared in normal atmosphere exhibits a sharp orange emission peaking at 591 nm excited by 221nm light, which is intrinsic f-f transition generated from Eu3+. Whereas, the phosphors Sr3Al2O6:Eu and Sr3Al2O6:Eu,Dy prepared in a weak reducing atmosphere show both a sharp orange emission peaking at 591nm excited by 221-nm light and a broad green emission peaking at 510nm excited by 328nm light, which resulted from Eu2+ transition between 4f65d1 and 4f7 electron configurations. The investigation results suggest that Eu3+ and Eu2+ co-exist in Sr3Al2O6 matrix synthesized in weak reducing atmosphere. In all samples, only Sr3Al2O6: Eu, Dy prepared in a weak reducing atmosphere has high intensity afterglow after excited by the UV source. The decay curve of Sr3Al2O6: Eu, Dy phosphor contains the rapid-decaying process and the slow-decaying process and can be fitted by a bi-exponential decay function. The measurement of thermal simulated luminescence demonstrates that only appropriate deep trap energy level and high trap concentration can generate optimum long-afterglow performance.