The Synthesis And Luminescence Properties Research Of Red Long Lasting Persistent Materials

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 I_626nm/I_539nmis 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:Ti^{4 +}(0.01≤x≤0.04)are synthesized. After doping Ti⁴⁺, the series of samples Y₂O₂S:Ti^{4 +}_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⁺,Ti^{4 +}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.