Synergistically improving luminescent properties of Eu2+, Dy3+ co-doped melilite with Bi3+ coupling

Abstract

The improvement of luminescent properties is important for expanding the application of long afterglow phosphor (LAP). Here, the melilite-type Sr1·97MgSi2O7: Eu2+0.01, Dy3+0.02 LAP was studied with Bi3+ as the second co-dopant. Both photoluminescence (PL) and thermoluminescence (TL) were improved in terms of intensity and afterglow lifetime when the doping concentration of Bi3+ exceeded 2.5 mol%, and the optimized point was 3.5 mol%. As compared to the case of Eu2+ - Dy3+ double doping, the improved PL of Eu2+ - Dy3+ - Bi3+ triple doping samples was attributed to better photon absorption. The improved TL and afterglow were attributed to the synergistic strengthening density of the traps by Bi3+ and the deepening of trapping by Dy3+, if their distance was sufficient close. As a result, both TL and afterglow optimized at a concentration of 2 mol% Dy3+ - 3.5 mol% Bi3+ coupling.