The Synthesis and Luminescence Properties Research of Red Long Lasting Persistent Materials
|Course||Materials Physics and Chemistry|
|Keywords||LLP Y2O2S MgSiCO3 Thermoluminescence|
The green long-lasting phosphors had been carried out industrialization produce since 1990s. After that, the green and blue LLP materials’ performance has gotten great improvement. However, the red LLP material has not been carried out commercial produce widely because of its short afterglow time, low luminescence intensity and poor environmental adaption. In order to improve the red LLP materials’ abilities and synthesize new red LLP materials, this paper does a series of researches about Y2O2S:Eu3+,Mg2+,Ti4+ which is the best red LLP material now. In addition, Y2O2S:Ti4+ is synthesized and its luminescence property is investigated. And then, we synthesize a new kind of red LLP material: Gd2O2CO3:Eu3+,Mg2+,Ti4+ and found it has a potential application in Hg-free fluorescent lamp. A silicate luminescent material MgSiO3:Mn2+,Dy3+ is synthesized and its luminescence property is researched in this paper. From these works above we can get following contusions:1. Using mixed flux method, a series of samples of Y2O2S:Eu3+,Mg2+,Ti4+ are synthesized . The investigation result indicates that the red orange ratio of I626nm/I539nmis gradually increased with the increasing of Eu3+ contents and it gets a max while the contents of Eu3+ arrive to 0.06. When the contents of Eu3+, Mg2+, Ti4+ are 0.002, 0.02,0.02 , the sample Y2O2S:Eu3+0.002,Mg2+0.02,Ti4+0.02 has the greatest brightness and the longest lasting time （5hours）. However, the afterglow colour of it is orange.When the contents of Eu3+, Mg2+, Ti4+ are 0.06, 0.02,0.02 , the long lasting time of sample Y2O2S:Eu3+0.06, Mg2+0.02,Ti4+0.02 decreased to 3h but the afterglow color of it near the standard red . Moreover, while added the Bi3+in the best sample, the long lasting time can be closed to 3.5 hours. Finding that the series samples : Y2O2S:Eu3+x,Bi3+（0.01≤x≤0.10） have good photoluminescence properties in VUV region. The best sample shows a excellent optical properties when compared with the commercial （Y,Gd）BO3:Eu3+ and it’s luminescence intensity arrives to 80% of commercial （Y,Gd）BO3:Eu3+ . Using mixed flux method, series of samples Y2O2S:Ti4 +（0.01≤x≤0.04）are synthesized. After doping Ti4+, the series of samples Y2O2S:Ti4 +x（0.01≤x≤0.04） have red-orange LLP properties and the strongest emission peaks are located in 574nm. The investigation shows that the best doping contents of Ti4+ is 0.03 and the sample’s long lasting time is 2 hours.2.Through investigating the defects states and electron states densities of Y2O2S:Eu3+,Mg2+,Ti4+,Bi3+, we find that doping Mg2+,Ti4+,Bi3+ ions can reduce the trap depth of Y2O2S:Eu3+ and change the moving mode of current carriers, which improves the long lasting performance of Y2O2S:Eu3+.3.Using mixed flux method , a series of samples of Gd2O2CO3:Eu3+,Mg2+,Ti4 +are synthesized. The investigation shows that after doping Eu3+,Mg2+,Ti4+together, the samples have LLP abilities. The best doping contents of Eu3+,Mg2+,Ti4+ are 0.05, 0.02,0.02.Besides,finding that the series samples of Gd2O2CO3:Eu3+x （0.01≤x≤0.0.08） have good luminescence properties under vacuum ultraviolet （VUV） excitation.4.Series of samples: MgSiO3:Mn2+,Dy3+ are synthesized by deposition method. While doping Mn2+and Dy3+ in MgSiO3, the sample’s crystal structure changes form clinoenstatite phase to protoenstatite phase. The sample MgSiO3:Mn2+,Dy3+ has a red LLP property but its afterglow time is short relatively. The best doping contents of Mn2+and Dy3+ are 0.04, 0.01. Through the investigation of thermoluminescence （PL） curves and positron annihilation （PA）, we find that while doping Dy3+ inMgSiO3:Mn2+ sample, holes are trapped by （?） and （?） clusters and thenare transported to the trapping centre which locates in the luminescence center of Mn2+. Finally these trapped holes combined with electrons are annihilated and haveLLP phenomenon. The defects of （?） clusters may be the reason of LLP.