Eutectic Al₂O₃/Y₃ Al₅O₁₂ fibers modified by the substitution of Sc₂O₃, Fe₂O₃ or Cr₂O₃

A variety of corundum/garnet eutectic fiber samples were produced by the micro-pulling-down (μ-PD) method in an Ar atmosphere and the substitution of Cr₂O₃, Fe₂O₃ or Sc₂O₃ for Al₂O₃ in the eutectic fiber sample 0.81Al₂O₃0.19Y₂ O₃ was studied by a scanning electron microscope (SEM) and electron backscattering (EBSP) together with the X-ray diffraction (XRD). Although the chemical substitution resulted in the formation of a colony structure consisting of a fine ordered "Chinese-script" structure of corundum and garnet surrounded by a thick boundary region, a fundamental crystallographic relationship 〈0 0 1〉 corundum// 〈1 1 2〉 garnet was found to be perpendicular to the solidification direction was readily observed. Cr₂ O₃ is distributed in corundum and garnet structures, Sc₂O₃, however, preferred the garnet structure. The EDX and XRD analyses showed that the presumably reduced FeO contributes to the formation of hercynite FeAl₂O₄.