The Combustion Synthesis And Photoluminescence Of Long Persistent Phosphors

Long persistent phosphors is that the phosphors can maintain their phosphorescence after remove of the excitation source. Long persistent phosphors has been widely studied and could be used in a variety of fields such as agriculture, industry and daily life since long persistent phosphorescence was found in 20 century. And its application in areas as storage display, the photo- electricity shift by solar energy, optoelectronics, life sciences, space navigation was investigated in recent years. However, limited work has just been done on studying the phosphorescence mechanism of the sort. So further study on long persistent phosphors is of great importance in theoretical and application fields due to its wide usage and great influence on the future science and technology.The recent progress ,synthesis method ,photoluminescence mechanism and long persistent luminescent models were reviewed firstly in this paper. The content and motivation of this paper was proposed on those bases. The polychrome long persistent phosphors were prepared by combustion synthesis and the main part of this paper were as follows.The green-emitting long persistent phosphor SrAl₂O₄:Eu²⁺,Dy³⁺was prepared by combustion synthesis and the influence of some processing conditions including initiating temperature ,union concentration, and different flux on its structure and luminescence was investigated. In addition ,the influence of Eu concentration, the ratio of Dy/Eu and the third rare earth ions on its luminescence was systematically and thoroughly studied.The blue-emitting long persistent phosphor CaAl₂O₄:Eu²⁺,Nd³⁺was prepared by combustion synthesis and the influence of above processing conditions on its luminescence was investigated. The mechanism of flux, co-doping rare earths and long persistent luminescence were discussed based on the studies on SrAl₂O₄:Eu²⁺,Dy³⁺ and CaAl₂O₄:Eu²⁺,Nd³⁺. B³⁺ P⁵⁺ ions most probably entered into the matrix during the synthesis, stabilized the pure phases and forced Eu³⁺ to change into Eu²⁺,and deepened the trap depth increased the trap density. With regard to the role of co-doping rare earths, it was not determined unilaterally by rare earth or by matrix whether the rare earths could improve the phosphorescence property. Furthermore, there seemed to be a matching connection between them. Finally, the experimental phenomena were explained by the phosphorescence mechanism proposed by Abanti Nag.The red-emitting phosphor was successfully prepared by combustion synthesis. And the influence of some processing conditions such as raw materials, initiating temperature,union concentration, H3BO3 concentration and co-doping rare earths on its luminescence was investigated. Both red-emitting Mg₂SiO₄:Mn,Dy and MgSiO₃:Mn ,Dy were monoclinic structure. But phosphorescence property of red-emitting Mg₂SiO₄:Mn,Dy was not as good as those of SrAl₂O₄:Eu²⁺,Dy³⁺andCaAl₂O₄:Eu²⁺,Nd³⁺.This paper was motivated to enhance the knowledge of phosphorescence mechanism, the role of flux and the influence of rare earths based on the experiment and analysis, know well the method which could improve phosphorescence property, find the reasons why phosphorescence property would be improved, optimize the processing technology and extend the application of long persistent phosphors.