Properties of Long Afterglow SrAl_2O_4:Eu~(2+), Dy~(3+) Phosphor

SrAl_2O_4:Eu~（2+）, Dy~（3+） powder phosphors were synthesized by solid-state reaction process. Based on the XRD peaks, the powder phosphors were identified as SrAl2O4 phase, which is monoclinic(a=8.4428A, b=8.822A, c=5.160?A, β=93.415°). These phosphors exhibited broadband peaks in both the excitation and emission spectra. The excitation peaks lied between 300nm and 450nm, and the main emission peaks lied around 518nm. The results indicate that the luminescence of these phosphors are due to 4f65d→4f7(8S7/2) transition of Eu2+. And its luminescence decay consists of the initial fast process and the later extremely slow process. The trap level of phosphors was analyzed through thermoluminescent spectra, which consists two peaks. This means that there are two electron traps in SrAl2O4: Eu2+, Dy3+, which can cause the long afterglow of the phosphors. The trap depths measured are 0.38eV and 1.34eV respectively.