Optimization of Sintering Conditions for Cerium-doped Yttrium Aluminum Garnet

Abstract

YAG:Ce phosphors have become widely used as blue/yellow light converters in camera projectors, white light emitting diodes (WLEDs) and general lighting applications. Many studies have been published on the production, characterization, and analysis of this optical ceramic but few have been done on determining optimal synthesis conditions. In this work, YAG:Ce phosphors were synthesized through solid state mixing and sintering. The synthesized powders and the highest quality commercially available powders were pressed and sintered to high densities and their photoluminescence (PL) intensity measured. The optimization process involved the sintering temperature, sintering time, annealing temperature and the level of Ce concentration. In addition to the PL intensity, samples were also characterized using particle size analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The PL data was compared with data produced from a YAG:Ce phosphor sample provided by Christie Digital. The peak intensities of the samples were converted to a relative percentage of this industry product. The highest value for the intensity of the commercial powder was measured for a Ce concentration of 0.3 mole% with a sintering temperature of 1540°C and a sintering dwell time of 7 hours. The optimal processing parameters for the in-house synthesized powder were slightly different from those of commercial powders. The optimal Ce concentration was 0.4 mole% Ce, sintering temperature was 1560°C and sintering dwell time was 10 hours. These optimal conditions produced a relative intensity of 94.20% and 95.28% for the in-house and commercial powders respectively. Polishing of these samples resulted in an increase of ~5% in the PL intensity.