Can orientations of directionally solidified dual-phase Al₂O₃/YAG eutectics be induced by single-phase sapphire seeds?

Directionally solidified dual-phase Al₂O₃/Y₃Al₅O₁₂ (YAG) eutectic ceramics (DSECs) typically exhibit strong anisotropy. To improve their properties, various single-phase sapphire seeds, including r-axis [1-102], m-axis [10-10], c-axis [0001], and a-axis [11-20], were used as seeds to induce the orientation of the Al₂O₃/YAG DSECs. The results showed that Al₂O₃ in the eutectics could be governed by the sapphire seeds. The YAG in each induced eutectic had a specific growth direction endowed by Al₂O₃ in the as-induced eutectics or the sapphire seed. Herein, we calculated the planar lattice misfits and interfacial strain energies of four crystallographic orientation relationships based on the constructed lattice models. It was elucidated the constraint of the sapphire seed caused YAG to grow following the rule of minimizing the interfacial strain energy. This revealed the reason why Al₂O₃/YAG DSECs orientation can be successfully induced. These results may provide a novel method for the design of high-performance eutectic ceramic materials.