Low-temperature formation of eutectic structures by reactive flash sintering of Al₂O₃–Y₂O₃ composites

Reactive flash sintering (RFS) has garnered significant interest because of the simultaneous synthesis/reaction and sintering of multicomponent ceramic materials. While electric fields demonstrably accelerate reaction kinetics during RFS, the reciprocal effect of reactions on flash sintering (FS) remains unknown. In this study, the role of the solid-state reaction in the onset of FS was investigated using Al₂O₃–Y₂O₃ and Al₂O₃–Y₃Al₅O₁₂ (YAG) as models. The results show that the onset temperature of FS of Al₂O₃–Y₂O₃ is 350 °C lower than that of Al₂O₃–YAG under a constant electric field of 1000 V/cm. This demonstrates that the solid-state reaction significantly reduces the onset temperature, likely by enhancing the electrical conductivity of the sample. Remarkably, Al₂O₃–YAG ceramic composites with fine eutectic structures were prepared by RFS-ed Al₂O₃–Y₂O₃ at a furnace temperature of 850 °C, which is far below the eutectic temperature. The resultant eutectic ceramics exhibited mechanical properties comparable to those of conventionally solidified counterparts. RFS is expected to be an energy-efficient and sustainable sintering technology to fabricate high-performance eutectic ceramics.