Orientation relationships of seed crystal-induced Al2O3/GdAlO3 eutectic ceramics

Al₂O₃-based directional solidified eutectic ceramics (DSECs) have long faced limitations in fracture toughness, hindering their practical applications. To address this challenge, we propose an innovative approach utilizing single-crystal c-sapphire as a seed to fabricate dual-phase Al₂O₃/GdAlO₃ (GAP) DSECs. The resulting eutectic ceramics exhibit coexisting regular fibrous and irregular Chinese script morphological features, where the crystallographic orientation of Al₂O₃ is inherited from the seed while GAP develops dual growth orientations governed by epitaxial relationships with Al₂O₃. Theoretical analyses based on interface matching principles reveal that low planar mismatching (<12%) critically enables the successful synthesis of this heterostructure. The designed orientation modulation coupled with tailored eutectic morphology synergistically enhances mechanical performance, achieving a hardness of 18.5 ± 0.5 GPa and fracture toughness of 5.3 ± 0.6 MPa·m^1/2. This work establishes a paradigm for optimizing mechanical properties in directional solidification systems through crystallographic orientation control.