| Based on the three colors principle,mixing the green,blue,red phosphors with a certain proportion can regulate the light of any color.Currently,blue and green fluorescent materials have been well developed to meet the daily needs of the people.But the red fluorescent material has always been a bottleneck in this technology.Despite the developed of a variety of red fluorescent material,there have a common weakness;luminous intensity is not high enough,short time afterglow and so on,which have limited their commercial application.As is well known,CaTi03:Pr3+ due to the chromaticity coordinates of pure red and is very close to the ideal,stable,have good fluorescence and afterglow performance,etc.has been attracted considerable attention.After decades of research found that in the name of the component is Ca0.8Zn0.2TiO3:Pr3r have a large improvement on the fluorescent properties as to the CaTiO3:Pr3+.Nevertheless,compared to the commercially available blue and green phosphors but still there is a big gap.So how to improve initial luminance and afterglow time of praseodymium-doped titanate red phosphor is urgent.The main contents of this thesis are how to improve the fluorescence properties of CaTi03:Pr3+ fluorescence properties,and explore its afterglow mechanism.Hollow sphere structure of Ca0.8Zn0.2O3:Pr3+ was successfully synthesized by hydrothermal method with citric acid as a complexing agent and urea as a precipitating agent.When urea and citric acid with Ti molar ratios of 2:1 and 1:1,respectively.Hydrothermal 220 ? for 2 h can obtain the best morphology,after calcined at 1130 ? for 5 h the sample have an excellent fluorescence properties.At the same time,we found under the Ostwald ripening process with a suitable value of pH(6-8),can obtain the sphere structure.Finally,by the Kirkendall effect the hollow has formed.Improved the conventional solvothermal method,by using a high concentration of metal salt solution as a metal ion source,both to avoid the direct addition of solid salt leads to inactivation of metal ions,but also to avoid too much water was added and lead to certain organic solvents insoluble insufficient.Using n-butanol as the solvent,tartaric acid as the complexing agent,solvothermal temperature at 200 ? for 2 h.Finally,calcined at 1130? for 5 h can obtain the sample.At the same time,this method for easily hydrolyze ions(Zn2+,Bi3+,Si4+,B3+)doping is very advantageous.By comparison we found that the use of this method for the synthesis of phosphors compared to the high temperature solid phase method,sol-gel method,hydrothermal method in performance has a great advantage.Used the solvothermal method to prepare the mixed phase phosphors of CaTi03-nZn2TiO4,CaTi03-kCa2Zn4Tii6O38:Pr3+.Compare to the tradition phosphor of Ca0.8Zn0.2TiO3,the CaTiO30.15Zn2TiO4:Pr3+phosphor has greatly improved in the optical property.Preliminary explore the mechanism of doping the Zn2+ in the CaTiO3:Pr3+ and improve the fluorescence properties.Not only Zn2+ doping form the new cavity in the CaTiO3,but also the Zn2Ti04:Pr3+ has a strong absorbed in the 300-400nm.Explores the afterglow mechanism of CaTiO3:Pr3+,suggested the afterglow is depending on the charge transfer from Pr4+ and Pr3+. |
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