Long Afterglow Luminescence Mechanism of SrAl2O4-based Phosphor by the Thermoluminescence and Positron Annihilation Method

Long afterglow SrAl2O4:Eu,Dy phosphor was prepared by the traditional ceramic synthesis method, and investigated its luminescent mechanism and properties by the thermoluminescence and positron annihilation method. The results indicate that Eu2+ ions act luminescent centers and Dy3+ ions as trap levels. The positron annihilation experiment reveals that traps with negative charge exist in the Sr0.94Al2O4: Eu-0.02 and Sr0.94Al2O4:Eu-0.02, Dy-0.04, the Dy3+ ions enter the Sr2+ sites, and produce some Sr2+ vacancies simultaneously. The thermoluminescence curves imply that the, depth of trap level is about 0.95eV while doped Eu ions simply, and 0.51eV while co-doped Dy3+ in the SrAl2O4 host. As for the long afterglow luminescence mechanism, the trapped holes released from the trap levels are recombined with electrons accompanying with the luminescence, which result in the long afterglow. Due to the different depths of trap levels, the afterglow properties of phosphors vary greatly.