Studies On The Synthesis And Luminescence Properties Of Metal Ions Doped Zn₂SiO₄:Mn²⁺

Zn2SiO4:Mn2+ has been recognized as an efficient green phosphor on account of its strong photoluminescence and high color purity, and was widely applied in plasma display panels (PDPs) as well as mercury-free fluorescent lamps. However, the commercially available green phosphor Zn2SiO4:Mn2+ owned disadvantages such as long decay time and lower luminous efficiency, which limited the extensively applications for PDPs. Therefore, its decay time and luminous efficiency still need to be further improved to meet the needs of the display of PDPs. In this investigation, The Zn2SiO4:Mn2+ green phosphors were synthesized via solid-state reaction method and the sol-gel method, respectively. Their photoluminescence properties varying with the concentration of metal ions under VUV region were systematically studied. Moreover, the effect of heat treatment on their luminescence properties was also investigated. The research results would speed up their application in PDPs as well as mercury-free fluorescent lamps. The main contents of this paper are as follows:1.The photoluminescence character of green phosphor Zn2SiO4:Mn2+ is closely bound up with its preparation method. The experimental results exhibit that the sol-gel method is the preferable process to obtain high luminescent intensity, better morphology and short decay time. The synthetic temperature of sol-gel method is lower at least 100℃than traditional solid-state reaction method.2.The effect of heat treatment on their luminescence properties is very effective. The results show that the emission intensity of phosphors calcined in the mixture of nitrogen and hydrogen are stronger than those of the phosphors calcined in the other heating atmosphere, and the decay time of phosphors is shortened than commercial products. The activator of Mn2+ can be prevented from oxidizing by means of the mixture of nitrogen and hydrogen.3.The concentration of Mn2+ has an evident effect on phosphor's luminescence properties such as luminescent intensity and decay time. Under VUV (147nm) excitation, the quenching concentration of Mn2+ is about 0.04mol, but long decay time. The decay time could be shortened by increasing the concentration of Mn2+ while the luminescence intensity would be reduced. In order to obtain shorter decay time, the concentration of Mn2+ is chosen to be 0.08mol in this paper.4. The decay time of Zn2SiO4:Mn2+ is still too long for its application in PDPs, due to the doubly spin and parity-forbidden transition of Mn2+. In this paper, the influences of the some metal ions such as Mg2+,Ca2+, Ba2+, Ge4+, Y3+, Gd3+, Li+ on their luminescent properties of Zn2SiO4:Mn2+ phosphors were investigated. The results exhibit that Mg2+,Ca2+, Ba2+, Y3+, Gd3+ substitute for the site of Zn2+, Ge4+ replace the site of Si4+. Among these, Mg2+,Ba2+, Y3+, Gd3+ have favorable influences on the photoluminescence properties of Zn2SiO4:Mn2+, they not only enhance the luminescent intensity but also shorten the phosphor's decay time evidently.5.On the basis of optimum experimental results, scaling-up experiments have been performed via solid state reaction.