Ce 3+ Doped Al 2 O 3 -YAG Eutectic as an Efficient Light Converter for White LEDs.

Ce doped AlO-YAG eutectics were successfully grown by the horizontal directional crystallization method. The crystallization rate of eutectic growth was changed in the 1-7.5 mm/h range at a growth temperature of 1835 ℃. The microstructure of eutectic samples was investigated using scanning electron microscopy and X-ray microtomography. The intrinsic morphology of eutectic represents the stripe-like channel structure with a random distribution of the garnet YAlO (YAG) and AlO (sapphire) phases. The content of these phases in the stripes changes in the 52.9-55.3% and 46.1-47.1% ratios, respectively, depending on the growth rate of the crystallization of the eutectic samples. The luminescent properties of the eutectic demonstrated the dominant Ce luminescence in the garnet phase. The luminescence of the Ce ions in AlO has also been observed and the effective energy transfer processes between Ce ions in the AlO and YAG garnet phases were revealed under high-energy excitation and excitation in the UV Ce absorption bands of sapphire. The phosphor conversion properties and the color characteristics (AlO-YAG):Ce eutectic with different thicknesses were investigated under excitation by a blue LED. We have also tested the prototypes of white LEDs, prepared using a blue 450 nm LED chip and (AlO-YAG):Ce eutectic photoconverters with 0.15 to 1 mm thicknesses. The results of the tests are promising and can be used for the creation of photoconverters for high-power white LEDs.