Preparation And Properties Of Several Silicate Long Afterglow Phosphorescent Materials

Long afterglow phosphorescent materials were widely used in energy saving, safety protection, and so on. Silicate long afterglow phosphor project is a high technology with long–range development future and significant potential in market.New green phosphors Sr₂ZnSi₂O₇:Mn²⁺, Tb³⁺ were prepared by sol–gel method. The The properties and phosphorescent mechanism were also studied detailedly with various analytical measures. A series of excitation peaks are attributed to charge transfer band transition of Mn²⁺â†'2O^2-; he emission spectra of Sr₂ZnSi₂O₇:Mn²⁺, Tb³⁺ are mainly attributed to Mn²⁺ ions transition from 4^T₁（4^G） to 6^A)_1g（6S）; And this phosphor can be clearly seen with naked eyes in a dark room over 2 hrs after the irradiation source has been removed. As a sensitizing agent, Tb³⁺ effectively improve luminescence properties of the material. REn+（RE=Tb, Zr, Nb, Sm, Dy）ions were added respectively in Sr2ZnSi2O7:Mn²⁺ phosphor. The afterglow decay curves indicated that when sensitizing agent is Tb³⁺, the material has the best luminescence property. The best molar ratio of Mn²⁺ and Tb³⁺ is 0.01, 0.01. Thermoluminescence （TL） properties of Sr₂ZnSi₂O₇:Mn²⁺, Tb³⁺ were also investigated, and the trap depth can be estimated according to empirical equation.Another part of this present dissertation was exploring research work on CaAl₂Si₂O₈–based long afterglow photoluminescent materials. Phosphors CaAl₂Si₂O₈: Eu²⁺, Dy³⁺ were synthesized by sol–gel method, which was changed partly. The obtained phosphor powders are more pure than those of solid state and the particle size also became smaller. The characteristic of this phosphor can make Eu2+ enter into the matrix lattice CaAl₂Si₂O₈ more easily and effective number of luminescent centers increase, which were of great importance to improve the properties of photoluminescent materials. The decay time of the phosphors was prolonged because the suitable trap depth caused by the co–activation of Dy³⁺ ion. The optimum sintering temperature is 1100℃and the optimum content of Eu2+ and Dy³⁺are 0. 01 and 0.005 respectively. Adding an appropriate amount of boric acid flux,persistent after–glow time and relative initial brightness of the corresponding sample is more than 100 hrs and nearly 665 mcd/m2 after the ordinary fluorescent irradiation source has been removed. Red phosphors CaAl₂Si₂O₈:Mn²⁺ were firstly prepared by sol–gel method. Under 226 nm ultraviolet light irradiation, this phosphor shows obvious long–lasting phosphorescence that can be clearly seen with naked eyes in a dark room for 18 min after the irradiation source has been removed. Therefore, this phosphor will be a promising new kind of luminescent material for further investigation.