Abstract: 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 Sr_0.94Al₂O₄: Eu_0.02 and Sr_0.94Al₂O₄: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.

Key words: thermoluminescence, positron annihilation, long afterglow, trap level