Research On Rare Earth Dopted Yttrium Aluminum Garnet Phosphor Synthesized By Spray Pyrolysis

Rare Earth Dopted Yttrium Aluminum Garnet(YAG) Phosphor is regarded as the key material for the white LED application, its quality contributes to the properties of white LED remarkably, such as luminance intensity, working life, etc. The main synthetical methods of YAG phosphor include solid state reaction , co-precipitation , sol–gel, combustion,etc. Solid state reaction is a popular method for YAG phosphor because of its low cost and simple technique, but this method has its unavoidable disadvantages: Raw materials are difficult to be mixed evenly under the solid state condition; Pure phase YAG could be only obtained above 1600oC , and often the flux is need to be added and introduces the impurities; Phosphor particles are easy to agglomerate with high temperature annealing thus grinding process is necessary .The crystal structure of the phosphor particles are destroyed during the grinding process, which leads to degeneration of luminance and phosphor particles finally show wide size distribution and worse morphology.Spray pyrolysis is a kind of synthetic method combining with advantage of liquid phase; it becomes a focus on the luminescent materials in recent years]. Phosphor particles prepared by spray pyrolysis come from the suspended droplets, thus the particles show spherical morphology with even size and homogenous composition ,which is difficult for the other methods to be realized. Spherical particles have minimum scattering area, high packing density; which is beneficial to the luminescent intensity and lifetime of the devices.YAG +phosphor can be obtained at lower temperature by spray pyrolysis without flux and avoid the introduction of the impurity. Spray pyrolysis even has advantages in large-scale production.In our research project, we devised the spray pyrolysis device, and non-agglomerated, spherical YAG phosphor particles by spray pyrolysis, different experimental conditions which impact on the results were investigated. With the increase of solution concentration, the mean size of the particle prepared increases gradually.When the concentration increased from0.05 to0.8mol/L,the mean size of the particles increased from0.60 to 1.50μm. When the concentration of the solution further increased, the particle surface shows a rougher surface. The lower flow rate of nitrogen is,the longer the residence timeof particles is,the final particles present the solid spheroid.With fast flow rate of nitrogen,as a result,the residence time becomes short and particles appearhollow and broken morphology.The influences of doped content of Ce3+ and Gd3+ on the phosphor were investigated.when dopted content of Ce3+ is 0.01, the phosphor emission intensity was very low.With the increase of the doped content of Ce3+,the maximum of emission intensity appeared at the 0.08. Further increase the doped content of Ce3+,the phosphor emission intensity decreased accordingly.when the doped content of Ce3+ is 0.15, the emission intensity decreased seriously.With the increase of doped content of Gd3+,the phosphor emission intensity decreased accordingly,when the doped content of Gd3+ increased from 0.1...