Preparation of a Core-Shell Structured Al2O3/YAG:Ce Phosphor by a Spray Drying Method and Formation Mechanism.

The core-shell structured Al 2 O 3 /YAG:Ce phosphor was prepared by a spray drying method. The obtained samples show cubic Y 3 Al 5 O 12 structure, have a spherical shape with the size in the range of 1~8 μm and exhibit higher internal quantum yield compared to the samples prepared by co-precipitation. Based on the fact that the spray drying method can be employed to fabricate microencapsulate particles, the formation mechanism of the core-shell structured Al 2 O 3 /YAG:Ce phosphor was formulated. The slurry, which was mixed with micrometer Al 2 O 3 particles and polycations consisting of Y 3+ , Al 3+ and Ce 3+ , was atomized and shaped by the evaporation of droplets. In the process of solvent evaporation, the interparticle capillary forces make the self-assembly of polycations into the close-packed shell surrounding the Al 2 O 3 particles, because the polycations have a bigger diffusion rate than Al 2 O 3 particles. At last, the precursor was calcined at the temperature from 850 o C to 1250 o C for 2 h and then the core-shell structured phosphor was produced. Therefore, a novel idea for preparing core-shell structured phosphor is proposed. [ABSTRACT FROM AUTHOR]