Distribution Of Traps In Long Afterglow Phosphors And Its Effect On The Afterglow

With the development of the techniques of producing new type of material, long afterglow phosphor without radiation and pollution, the mechanism and process of its luminescence had also been studied extensively. The material can store energy and be kept in non-equilibrium for a long time after receiving a dose of radiation, which gives a great potential application for energy storage and photoelectric transfer. The local energy level lying in forbidden band is the primary reason for the characteristics. The ?main means of measuring local energy levels are EPR, thermo-luminescence and absorption spectrum etc. In this article, the distribution of local energy levels in long afterglow phosphors and its effect on afterglow were studied by means of thermo-lurninescence.Under different conditions, long afterglow phosphors SrAl2O4:Eu2+,Dy3+, CaAl2O4:Eu2+, Nd3+, La3+and CaTiO3: Pr3+ were synthesized by high temperature solid state reactions, and the distribution of traps in long afterglow phosphors of aluminates and titanium compounds and its effect on the afterglow were studied particularly.The distributions of thermo-luminescence peaks are determined by several factors such as excitation source, excitation dose, synthesis temperature, configurations of raw materials as hosts, content of rare earth ions and flux. And then the distributions of traps in phosphors were also determined at the same time. The trap capture rates for carriers was influenced by a few factors, such as the radius of dopant atoms, occupied positions in crystal lattices and proper dopant concentration. The more carriers captured by traps indicated the stronger intensity of thermo-luminescent peaks. The phosphors with strong thermo-luminescent peaks showed good characteristic of long afterglow.