The characterization and mechanism of long afterglow in alkaline earth aluminates phosphors co-doped by Eu2O3 and Dy2O3

Long afterglow alkaline earth aluminates MAl2O4:Eu, Dy (M: Ca, Sr, Ba) phosphors were prepared at high temperature and weak reductive atmosphere. The excitation and emission spectra of these phosphors indicated that all of them are broad band, and the main emission peaks around 445, 496 and 518 nm of CaAl2O4:Eu, Dy, BaAl2O4:Eu, Dy and SrAl2O4:Eu, Dy, respectively, are due to 5d→4f transition of Eu2+. The decay curves implied that these phosphors contain fast-decay and slow-decay process. The thermoluminescence (TL) glow curves showed that the peaks of MAl2O4:Eu, Dy phosphors are 124, 77 and 173°C as the order of Ca, Sr and Ba in the MAl2O4:Eu, Dy (M: Ca, Sr, Ba) structure, respectively. The Dy3+ trap levels may be considered to be responsible for the long afterglow phosphorescence at room temperature.