Controlled Synthesis And Properties Of The Strontium Aluminates Long Afterglow Phosphors

Alkaline earth aluminate phosphors, which can glow in the dark, are widely usedin architectural decoration industry, traffic, military, emergency lighting, anti-fake.The optimization of the syntietic condition for synthesize efficient long afterglowphosphors have evoked increasing reasearch interest because of its disadvantages inlong afterglow bright and time, shape, and size.Strontium aluminate long afterglow phosphors was obtained by coprecipitationmethod in this paper. The effects of activator concentration, assistant activatorconcentration, synthetic temperature, H3BO3doping density, calcination time andcalcination temperature on the afterglow properties of the products have beeninvestigated in detail. And the synthetic conditions were optimized by orthogonalexperiments. Then the effects of different synthetic methods, transition metal ions andassistant activator on the afterglow properties, morphology and size of the productswere investigated. The main study of this paper are demonstrated as follows.(1) Strontium aluminate long afterglow phosphors was obtained by coprecipitationmethod. The effects of activator concentration, assistant activator concentration,synthetic temperature, H3BO3doping density, calcination time and calcinationtemperature on the afterglow properties of the products have been investigated indetail. The synthetic conditions were optimized by orthogonal experiments. Strontiumaluminate phosphors with the best long afterglow properties were obtained when setthe nEu/nSras0.03, nDy/nEuas2.5, WH3BO3/WPas10%and the calcination time as2.5h. Then the phosphors were synthesized by three different methods to optimized itsmorphology and size. The XRD and SEM analysis of the products demonstrated thatthe phosphors obtained by the three different synthetic methods were all composed ofSr4All4O25and SrAl2O4. The shape of the products synthesiszed by coprecipitationmethod and coprecipitation-microwave method were both irregular. The shape of theproducts obtained by coprecipitation-hydrothermal method was flake-like, spanningabout500nm in width and70nm in thickness. The afterglow spectra analysisdemonstrated that the phosphors, showed the best long afterglow properties, obtainedby coprecipitation method. The fluorescence spectra demonstrated that the phosphorssynthesised by the three different methods all emited green fluorescence at500nm,assigned to the electron transition from4f65d to4f7. (2) The effects of different transition metal ions and assistant activator on theproperties of the products were investigated. The results demonstrated that thefluorescence emission wavelength and X-ray diffraction peak position remained aboutthe same atter doping Mn2+, Ni2+, Mg2+. The X-ray diffraction peak position remainedabout the same but X-ray diffraction peak intensity assigned to Sr4All4O25increased,the fluorescence spectrum was blue shifted after doping Cu2+, Zn2+. The fluorescenceemission intensity decreased after doping transition metal ions for the excessive trapconcentration.The diping of different assistant activator exerted great effects on the crystallinefield, emission wavelength and long afterglow bright and time. The materials showedgreater afterglow performance after doping Dy3+, Ho3+or Er3+as the assistantactivator.