Preparation Of Novel Lithium Silicate Luminescent Materials And The Investigation Of Their Afterglow Mechanism

Long afterglow luminescent materials are photoluminescent materials that can emit light when excited by the external light source and absorb the light energy and store it in the form of light at the same time. When the activate light source is turned off, the energy it stored would release in the form of visible light at a relatively slow ratio. Due to this unique property, it has been put into use in many useful fields such as luminous materials, safety instructions brands,emergency lighting and so on. Among the massive kinds of long afterglow luminescent materials, Alkaline-earth lithium silicates possess stable physical and chemical properties, well water-resistance property, and can be easily prepared at a relatively low expense. Therefore it has been studied by many researchers. In this paper, two kind of afterglow mechanisms were presented aiming at finding out novel Alkaline-earth lithium silicates luminescent materials with better afterglow properties.Li2SrSiO4:Tb3+ samples of different concentrations were prepared through solid state reaction. XRD measurement performed to characterize crystal structure. Photoluminescent properties were characterized by PLE and PL,typical 5D4-7Fj transitions of Tb3+ ions were detected by PL. The effect of doping concentrations on the PL properties were further investigated to find out the concentration quenching point, and its mechanism was discussed using energy transition theory, the mechanism was confirmed as dipole-quadrupole interaction . The powder presented afterglow behavior after switching off the irradiation source. Afterglow decay curve were measured and fitted to characterize the afterglow properties, a triple exponential decay model was determined. Trap depth and the concentration were obtained through fitting the thermolum- inescence spectra of the samples, the trap depth was 0.38ev, the concentrion was 1.27×1010mol-1. Afterglow mechanism was proposed afterwards as the release of the electrons and holes and their recombination.Li2Ca0.4Sr0.6SiO4:Tb3+ samples of different concentrations were prepared through solid state reaction. XRD measurement performed to characterize crystal structure. Photoluminescent properties were characterized by PLE and PL, typical 5D4-7Fj transitions of Tb3+ ions were detected by PL. The effect of doping concentrations on the PL properties were further investigated to find out the concentration quenching point, and its mechanism was discussed using energy transition theory. The mechanism was confirmed as dipole-dipole interaction. The samples also presented afterglow behavior. Consistent with triple exponential decay model. Trap depth and the concentration were calculated, the trap depth was 0.43ev and the concentration was 3.86×1010mol-1afterglow mechanism was proposed afterwards as the release of the electrons and holes and their recombination.Orange-yellow emitting phosphors Li2Ca0.4Sr0.6SiO4:Eu2+ and Li12Ca0.4Sr0.6-SiO4:Eu2+, Dy3+ samples of different concentrations were prepared through solid state reaction. XRD measurement performed to characterize crystal structure.Luminescent properties were judged by PLE and PL, afterglow behavior was characterized by decay curve. Afterglow mechanism was discussed after fitting the thermoluminescence spectra, showing a typical orange-yellow afterglow. A notable enhancement of afterglow property of the Li2Ca0.4Sr0.6SiO4:Eu2+, Dy3+phosphors was observed. TSL results demonstrated that the trap depth and energy level were increased that prolonged the life time of metastable electrons.Therefore the afterglow behavior had been enhanced.