Investigation Of Red And Near Infrared Long Afterglow Phosphors

Long-lasting phosphorescence (LLP) is a type of special glow materials that store energy under proper excitation and after the excitation source is switched off and release the conserved energy by means of visible light. As the energy saving is increased, the red LLP materials have attracted considerable attention. 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 shot afterglow time, low luminescence intensity and poor environmental adaption. Therefore, the best performance red LLP materials have the most important practical significance. In this paper, a series of red or near infrared LLP with composition gallogermanates were synthesized by a high temperature solid-state reaction method, and a series of red phosphors of composition Sr2Si5Ng8:Eu2+were synthesized by a carbothermal reduction and nitridation method. The structure and luminescence properties of MgGa2O4:Cr3+by Zn substituted for Mg have been discussed. The structure and luminescence properties of ZnGa2O4:Cr3+by Ge or Si substituted for Ga have been researched. The structure and luminescence properties of Sr2Si5N8:Eu2+by different ratio k of SrC03and Si3N4have been discussed.(1)A series of red long afterglow phosphors with composition ZnxMg(1-x)Ga2O4: Cr3+(x=0、0.2、0.6、0.8、1.0) were synthesized by a high temperature solid-state reaction method. The X-ray diffraction studies show that phase of the phosphors is face-centered cubic structure. Photoluminescence spectra show that the near infrared emission of Cr3+originated from the transition of2E-4A2. The emission peaks moved from704nm to696nm excited by UV. The measurement of thermoluminescence peak moved from473K to384K excited by UV. The afterglow decay characteristics show that the phosphor samples with different Zn contents have different afterglow time and the afterglow time also changes with the value of x.(2) A series of red long afterglow phosphors with composition Zn(1+x)Ga(2-2x)Gex04:Cr3+(x=0、0.2、0.4、0.6、0.8、1) were synthesized by a high temperature solid-state reaction method. The X-ray diffraction studies show that phase of the phosphors is cubic structure ZnGa2O4for x≤0.4,where as the phase is trilateral structure Zn2GeO4for x>0.6. The photoluminescence spectra show that the red emission of Cr3+originated from the transition of2E-4A2and the transition of4T2-4A2.The red long afterglow luminescence mechanism of samples were discussed according to quantum tunneling. The measurement of thermoluminescence reveals that the trap depth of the phosphor samples with different Ge contents is different.(3) A series of red long afterglow phosphors with composition Zn(1+x)Ga(2-2x)SixO4:Cr3+(x=0、0.2、0.4、0.6、0.8、1) were synthesized by a high temperature solid-state reaction method. The X-ray diffraction and photoluminescence spectra of Zn(1+x)Ga(2-2x)SixO4:Cr3+phosphors are similar with Zn(1+x)Ga(2-2x)GexO4: Cr3+phosphors. But Zn(1+x)Ga(2-2x)Six04:Cr3+phosphors have a strong red long afterglow characteristics.(4) A series of red phosphors with composition Sr2Si5Na8:Eu2+were synthesized with different ratio k of SrCO3and Si3N4by a carbothermal reduction and nitridation method. The X-ray diffraction studies show that k=2.2is Sr2Si5N8:Eu2+. The photoluminescence spectra show that k=2.2is Sr2Si5N8:Eu2+too; The nternational commission on illumination studies show that the emission of k=2.2has high purity. It could combine with blue to white.