In the design of powder phosphors

the morphology and size of materials must be studied and controlled so that the desired objectives of improved powder phosphors can be achieved.It has been pre dicted that the optimum phosphor characteristics can be obtained with particle size on the order of 1μm. For the improved phosphors

the ideal morphology is that of perfect sphere. Spherical morphology is required for high brightness and high resolution. Additionally

high packing densities and low scattering of light can also be obtained by using spherical phosphors. A range of methods has been developed for the preparation of spherical particles. Spray pyrolysis is a newly developed method for the preparation of inorganic functional materials. In general

luminescent materials derived from this method have spherical morphology and fine narrow size distribution. In this method

a misted stream of precursor solution is dried

precipitated

and decomposed in a tubular furnace reactor. Particles produced by spray pyrolysis are relatively uniform in size and composition because of microscale reaction within a droplet and the lack of a milling process. Moreover

various preparation conditions have influence on the characteristics of particles prepared by spray pyrolysis.Therefore

the morphology

composition and size of particles can be controlled for good luminescent characteristics by changing the concentration of solution

spray rate

flowing rate of carrier gas and characteristics of solution. Accordingly

the luminescent intensity of powder phosphors prepared by spray pyrolysis can be improved with the changing of characteristics of particles caused by sintering temperature

morphology and size

crystallization and additive. Despite good luminescent performance

spray pyrolysis method also has a number of advantages such as simplicity of apparatus

low costing and without pollution. In conclusion

spray pyrolysis method can be a hopeful developing direction for preparation of powder phosphors.