Fabrication and Luminescent Properties of YAG:Ce Transparent Microspheres by Laser Heating

In this paper, YAG:Ce microspheres were fabricated by a laser heating method. The microspheres are polycrystalline. The melting of the YAG:Ce powder due to the extremely high temperature provided by the laser heating may account for the fast synthesis of the transparent YAG:Ce microspheres. Due to the temperature gradient during cooling, equiaxed and columnar grains were found inside the microspheres. The equiaxed grains are always located at the outer part of the spheres where large under-cooling was created. However, columnar grains are always found at the inner part of powder where a steep temperature gradient presented during cooling. The average size of the equiaxied crystallites observed from the SEM images is about 5 μm. The columnar crystallites are about 5 μm wide and 20 μm long. In the luminescence investigation, the optimum concentration of Ce³⁺ was found to be 2 at%. Furthermore, transparent spheres of other chemical compositions are also possible to be fabricated by this method, indicating its wide range of potential applications.