Combustion Synthesis, Surface Modification And Luminescent Properties Of SrMgAl₁₀O₁₇:Eu²⁺ Blue Phosphor For PDP

Plasma display panel (PDP) is a new type of flat panel display. Because of its large screen,high definition, large viewing angle, it is widely used in large-screen wall TV, high-definition television, multimedia display and many other fields. The trichromatic phosphors of PDP are excited by vacuum ultraviolet (VUV) of 147nm, are photoluminescence. Plasma phosphors are not only required to resistant VUV radiation, but also to have high efficiency and high color purity. Therefore, the plasma phosphors is the key factor that determines the quality of PDP, and how to prepare phosphors has become one of the key techniques of fabricating PDP. Blue phosphors BaMgAl₁₀O₁₇:Eu²⁺(BAM) which widely used in PDP have some disadvantages, such as poor thermal stability, serious luminance degradation under irradiation of VUV,which restrict the properties of PDP.Therefore,it is eager to develop new materials system to adapt to the development of high technology of PDP.At present, commercialized phosphors have been prepared by solid-state reaction process, which has advantages of simple process, high yield, and low cost et al. But this method needs high reaction temperature, leading to incomplete reaction. So it is difficult to obtain the products of uniform composition. In addition, the particle size of the phosphors which synthesized by the solid-sate reaction progress is relatively coarse. The phosphors usually need to go through milling grinding before their use, and milling grinding will lead to so many defects that the luminous efficiency of the phosphors decreased. Therefore, development of new process for preparing the phosphors is important for the improvement of the properties of the phosphors. Recently, a solution combustion synthesis has attracted considerable attentions as a new wet-chemical method. The combustion process prepares the precursor powders in low temperature within only a few minutes, which has been extensively applied to the preparation of various oxide materials.In this paper, SrMgAl₁₀O₁₇:Eu²⁺ phosphors were synthesized by combustion method. X-ray diffractometer (XRD), Field emission electron microscopy(FE-SEM),transmission electron microscope(TEM), luminescence spectrophotometer were used to analyze and measure the crystal structure, morphology, excitation and emission spectra. The main content of this paper includes the following: Blue SrMgAl₁₀O₁₇:Eu2+ phosphors were synthesized by combustion method. Influence of urea CO(NH2)2 mass fraction,activator Eu2+ mole fraction,flux H3BO3 mass fraction and Surface-active agent polyethylene glycol (PEG) on luminescent properties of products was investigated.The SrMgAl₁₀O₁₇:Eu2+ has also been modified by surface coating using sol-gel process, and the formation mechanism has been discussed. The main results are as follows:(1)Blue SrMgAl₁₀O₁₇:Eu2+ phosphors were synthesized by combustion method at 600℃. The product is pure phase. The emission spectrum shows a single intensive band centered at 472nm under ultraviolet (UV) 327nm excitation, which corresponds to 4f65d,�'4f7 transition of Eu2+. The urea CO(NH2)2 strongly affects the luminescence of SrMgAl₁₀O₁₇:Eu2+,when quality amount of urea is two times of its theoretical value, the maximum luminescent intensity is obtained.(2) Critical quenching content of Eu2+ in SrMgAl₁₀O₁₇:Eu2+ is 7%. Adding the moderate flux H3BO3 can improve the luminescence of the products. Because flux can reduce the diffusion resistance between the molecules and the ions, so it is conducive to the growth of grains. The best dasage of H3BO3 is 0.05.(3)The obtained SrMgAl₁₀O₁₇:Eu2+ phosphors prepared with PEG additive have better crystal properties. PEG additive can prevent phosphors from agglomeration. The maximum emission intensity of products is achieved when the Molecular Weight of PEG is 10000, the concentration of PEG is 1.25%.( 4 ) A thin SiO₂ coating was successfully obtained on the surface of SrMgAl₁₀O₁₇:Eu2+ phosphors by the sol-gel method. After the coating treatment, not only the luminescence intensity of SrMgAl₁₀O₁₇:Eu2+ phosphors has increased, but also the thermal stability of the phosphors has significantly enhanced.