| The persistent phosphors could be emitted long-lasting luminescence after activation by the special wavelength. In addation, storage energy properties have received much attention due to potential applications in many technical fields. Three noval persistent phosphors were prepared in this thesis to resolve the different areas of applications. The persistent phosphors of tranditional aluminate are not satisfied for applicating of outdoor and biomass environments, as their poor moisture and water resistance. However, silicates are suitable hosts of phosphors because of their high chemical and physical stability, especially their excellent water resistence ability. So host of silicate is very suitable for persistent phosphors.We synthesised three kinds of silicate-base persistent phosphors by solid state reaction method for different areas of application. Firstly, the persistent phosphor of Ba4(Si3O8)2: Eu2+,Pr3+ is used for reducing frequency twinkle problem in the alternate crrent AC-LED. Second, materials of Ba4(Si3O8)2:Eu2+,Er3+ can emit near-infraed persistent luminescence after stoppage excitation. This material will be applied to vivo bio-imaging areas. Thirdly, we parpeared a sunlight activated long-lasting luminescence from Ba5Si8O21:Eu2+,Dy3+ phosphor. This visible-light persistent phosphor is commonly used as self-sustained night vision materials.The main contents are listed as following:A bluish-green long persistent luminescence material Ba4(Si3O8)2:Eu2+,Pr3+ was synthesized by traditional solid state method in the reductive atmosphere. We found that both of photoluminescence or afterglow procedures have same emission center of Eu2+. The cation of Pr3+ co-doped would change the depth and distribution of traps in this phosphor. The Eu2+/Pr3+ co-doped sample can emit strongly persistent luminescence, due to extinction of high temperature traps. And relationship of competition in electron capture process is disppear between deep and shallow traps. In addation, initial intense of afterglow was greatly improved, because of the shallow traps further close to low temperature ares of Thermoluminescence (TL). The result of afterglow intense is different with different irradiation energy. It is contribute to unlike excitation pathways. Under high energy excitation, the electrons of host will be activated to forbidden band and then be captured by traps. Under relative low energy, the electrons of emission center of Eu2+ will be activated to exciated state of Eu2+. And then electrons are captured by traps via conductive band. This persistent phosphor could emit bright photoluminescence and initial afterglow that be using to AC-LED by alternative crrucent.Under 365 nm excitation, the phosphor of Ba4(Si3O8)2:Eu2+,Er3+can emit lasting visble and NIR light. We found that energy transfer was happened between Eu2+and Er3+. It made the emission center of Er3+ to emit 1530 nm NIR light. This material will be potential applied to vivo bio-imaging areas.We report a novel visible long-lasting luminescence phosphor of Ba5Si8O21:Eu2+,Er3+ for the first time. This phosphor could be activated effectively by sunlight or even in severe weather conditions, which is mainly attributed to the broad excitation spectrum highly responds to UV-A and violet-light in the solar spectrum. Three kinds of emission cencters of Eu2+ have same decay rate in afterglow. And afterglow decay curve indicate that have two decay procedures- quick and slow decay. According to TL cuves, we found that deep traps can be better filled with electrons that shallow traps after by low-enenrgy excitation. There results disobey traditional afterglow mechanism, and we propose a new mechanism that quantum tunneling was happened in slow decay. And traditional mechanism was taken place in quick decay period that is shown intense persistent luminescence and short last-time. Moreover, phosphors exhibits excellent and stable phosphorescence even in the water, indicating that it will be an all-weather material that can be effectively and repeatedly charged by natural daylight in the all kinds of open-air environment. Furthermore, the quantum tunneling behavior was illustrated in the afterglow mechanism. |
PDF Full Text Request