Microstructure and Crystal Chemistry of Eutectic Al₂O₃/Y₃Al₅O₁₂Fibers Modified by the Partial Substitution of SC₂O₃for Al₂O₃.

Al₂O₃(corundum)/Y₃Al₅O₁₂(garnet, YAG) eutectic fiber samples were produced by the micro-pulling-down (μ-PD) method and the substitution of SC₂O₃for Al₂O₃in the Al₂O₃/Y₃Al₅O₁₂eutectic fibers was studied by a scanning electron microscope (SEM) and electron backscattering diffraction (EBSD) together with X-ray diffraction (XRD). The substitution of SC₂O₃up to 5mol% appears to enhance the formation of the colony texture in the typical “Chinese script structure” with an ordinary crystallographic relationship of [110] corundum // [111] garnet parallel to the solidification direction and [001] corundum // [211] garnet perpendicular to the solidification direction. Nevertheless, the further substitution up to 10mol% SC₂O₃induced the primary growth of garnet rods parallel to the solidification direction, and the gap among them was filled by another Chinese script structure with the novel crystallographic relationship of [001] corundum // [100] garnet parallel to the solidification direction. The preference of Sc at the dodecahedral site of the garnet structure, was also confirmed by the single crystal X-ray diffraction.