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

Ce 3+ doped Al 2 O 3 -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 Y 3 Al 5 O 12 (YAG) and Al 2 O 3 (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 3+ luminescence in the garnet phase. The luminescence of the Ce 3+ ions in Al 2 O 3 has also been observed and the effective energy transfer processes between Ce 3+ ions in the Al 2 O 3 and YAG garnet phases were revealed under high-energy excitation and excitation in the UV Ce 3+ absorption bands of sapphire. The phosphor conversion properties and the color characteristics (Al 2 O 3 -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 (Al 2 O 3 -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.