Directionally Solidified Al₂O₃/Er₃Al₅O₁₂ and Al₂O₃/Yb₃Al₅O₁₂ Eutectic Ceramics Prepared by Optical Floating Zone Melting

Al₂O₃/Er₃Al₅O₁₂(ErAG) and Al₂O₃/Yb₃Al₅O₁₂(YbAG) eutectic rods with fine and homogeneous microstructure, free from cracks or pores, were directionally solidified using optical floating zone method at growth rate of 10 mm/h. The crystallographic orientation, preferred orientation, and 3D distribution of Al₂O₃ and Er₃Al₅O₁₂/Yb₃Al₅O₁₂ phases in the terminal growth zone of Al₂O₃/ErAG and Al₂O₃/YbAG eutectics were investigated by EBSD and high-resolution X-ray microscope. Vickers hardness of the as-prepared Al₂O₃/ErAG and Al₂O₃/YbAG eutectics are determined as (13.5±0.4) and (12.8±0.1) GPa, respectively. The fracture toughness results of Al₂O₃/ErAG and Al₂O₃/YbAG are (3.0±0.2) and (3.2±0.1) MPa•m^1/2, respectively.