| White light-emitting diode (W-LED), with lots of excellent properties, such as energy saving, long lasting life, non-pollution, low applied voltage and fast startup, is to be the fourth era lighting lamp-house source. The white LED consisting of a blue LED and yellow emitting Y3Al5O12:Ce (YAG:Ce) is the main route, but it has a low luminescent efficiency. Phosphors with high efficiency (non-aggregation, fine particles and regular morphology (sphericity) ) can improve the luminescent efficiency of W-LED effectively. YAG:Ce phosphor can be prepared by solid reaction, sol-gel processing, combustion synthesis , spry pyrolysis and precipitation method. But these methods can not satisfy all requirements of phosphors.The spherical precursors of Y3Al5O12:Ce powders were prepared by the continuous reaction-precipitation process using NH4HCO3, NH4Al(SO4)2·12H2O, Y2O3 and Ce2O3 as the starting reagents. The precursor and its products were characterised by FTIR, SEM, EDS, XRD and TG-DSC. It was found that pH values, concentrations and velocities of flow effected surface shapes of samples profoundly. The results show that the spherical precursors of Y3Al5O12:Ce were prepared under the optimized processing conditions (pH=7.5, C[Al3+]=0.40mol/L and V(([A13++Y3+])=0.35ml/min). Non-aggregation and spherical Y3Al5O12:Ce powders were obtained from sintering the precursors at 900℃ for 2 hours in reducing atmosphere, and the formation temperature for Y3Al5O12:Ce was approximately 600℃ lower than traditional high temperature solid-reaction method. In addition, the formation mechanisms of the spherical precursors and YAG phase were discussed as well. Excitation and emission spectrums of YAG:Ce were characterised by Fluorescence Spectrophotometer. Ce concentration and heal temperature effet the emission spectrums of YAG:Ce greatly. Heal treating at 500℃ for a long time in air atmosphere, or acid or alkali treating could lead the decrease of luminescence intensity of YAG:Ce powders.
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