Preparation And Properties Of Ultra-long Afterglow Phosphors

Strontium aluminate long-lasting phosphors were concerned in recent years because of its excellent performance and applied more and more extensively. Strontium aluminate phosphors are a kind of photo luminescent materials with stable performance,high efficiency,light-storing in daytime,light-showing in night. They are widely used in low-level lighting,direction instructions and decorative landscaping with significant applied value. Light-storing-type lamps and direction on the ground or in the wall can be used when faults appear in the power system because fire or earthquake happen. Ultra-long-lasting phosphors material is an ideal green light with important scientific significance and value for its study which showed enticing prospect.In this thesis, the preparation and properties of strontium aluminate long afterglow phosphors with different composition were studied.At first, starting from high pure alumina, the yellow-green luminescence material SrAl₂O₄:Eu²⁺,Dy³⁺ superfine powders with pure phase and better luminescent performance were prepared via a dipping process or a thermo-precipitation. The influences of different conditions on the powder morphology,phase structure and properties of ling-lasting luminescence were studied. The results indicated that pure monocline SrAl₂O₄:Eu²⁺,Dy³⁺ can be successfully synthesized via the dipping process without the disturbance of hexagonal phase. Simultaneously the influence of the adding method of H3BO3 on the phase structure was studied. A precurcer with a special coating nano-structure can be obtained via the thermo-precipitation method. Successively the purer phase of monocline SrAl₂O₄:Eu²⁺,Dy³⁺ can be prepared after the powders were calcined. The influence of H₃BO₃ content on the phase structure properties of phosphors were discussed, as well as the content of the activating agent. In addition, ML properties of yellow-green phosphors were studied and the results reveal that as-prepared phosphors have higher sensitivity than the commercial product. The ultra-long afterglow luminescence materials with high afterglow brightness can be synthesized at low socking temperature of 1000℃by above two simple methods.A new method, sol-hydrothermal method, has been employed in the synthesis of blue-green luminescent material. In the stage of precursor preparation, the raw material of SrO was dispersed homogenously into a sol solution containing Al³⁺,Eu³⁺,Dy³⁺. Then the mixture was treated by the hydrothermal process. At last, as-obtained powders surrounded by activated carbon was calcined at 1300℃with a reducing atmosphere in order to synthesize the luminescent material of Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ with better crystal form, high luminescent efficiency and ultralong afterglow time. The influences of different precipitant on phase structure and luminescent performance were discussed. The as-prepared blue-green luminescent material also has better ML property than commercial powder.