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

摘要:

采用喷雾干燥法制备核壳结构的Al2O3/YAG:Ce荧光粉，所得样品为立方Y3Al5O12结构，球形颗粒的粒径为1~8 μm，显示出比共沉淀法高的内部量子效率。核壳结构的Al2O3/YAG:Ce荧光粉的形成机理为，起始悬浮液包含微米级的Al2O3和Y3+、Al3+、Ce3+等形成的聚阳离子，经过雾化形成小液滴，在溶剂挥发过程中，由于聚阳离子比微米级的Al2O3的迁移速度大，在颗粒间的毛细管力的作用下，自组装成为聚阳离子包裹微米级的Al2O3的核壳型结构，在850~1250 ℃时焙烧2 h，就得到了核壳型的荧光粉。

Abstract:

The core-shell structured Al2O3/YAG:Ce phosphor was prepared by a spray drying method. The obtained samples show cubic Y3Al5O12 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 Al2O3/YAG:Ce phosphor was formulated. The slurry, which was mixed with micrometer Al2O3 particles and polycations consisting of Y3+, Al3+ and Ce3+, 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 Al2O3 particles, because the polycations have a bigger diffusion rate than Al2O3 particles. At last, the precursor was calcined at the temperature from 850 oC to 1250 oC for 2 h and then the core-shell structured phosphor was produced. Therefore, a novel idea for preparing core-shell structured phosphor is proposed.