Investigation on charging processes and phosphorescent efficiency of SrAl₂O₄:Eu,Dy

An optical charging process of SrAl₂O₄:Eu,Dy has been investigated to examine its efficiency. In the charging process, the luminescence grows gradually before reaching the equilibrium intensity. The unreleased area above the charging curve represents the energy stored in the traps. It is found that the integrated intensity of the released phosphorescence after excitation is larger than that of the unreleased luminescence in the charging process. Under an intensive excitation, a decrease course of the luminescence in the charging process is observed. A quenching mechanism via cross relaxation among Eu²⁺ ions is proposed. The quantum efficiency is measured by comparing the integrated intensities of the phosphorescence and the pump light.