Eutectic Al2O3/Y3Al5O12 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 0.81Al2O30.19Y2O3 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. Cr2O3 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.