Dual-phase eutectic ceramics with improved hardness and toughness via nano-coherent high-entropy oxides.
basic_science · Level V
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- Record sourced from PubMed, PMID 42285971.
- Also identified by DOI 10.1038/s41467-026-74505-y.
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Abstract
Alumina-based eutectic ceramics exhibited high high-temperature strength but their intrinsic brittleness constrained broad structural applications. Here, we broke this limitation by introducing high-entropy rare-earth aluminate (REAlO<sub>3</sub>, RE = Gd<sub>0.25</sub>Eu<sub>0.25</sub>Nd<sub>0.25</sub>Sm<sub>0.25</sub>) into the Al<sub>2</sub>O<sub>3</sub> matrix via directional solidification. The resulting dual-phase eutectics exhibited a unique architecture where single-crystalline Al<sub>2</sub>O<sub>3</sub> was interlocked with bicrystalline high-entropy REAlO<sub>3</sub>, forming nanoscale coherent grain boundaries (~57.5 nm) and semi-coherent phase boundaries (lattice misfit <5.1%). The tailored microstructure and orientation relationship enabled a synergistic enhancement of Vickers hardness (19.4 GPa) and fracture toughness (5.5 MPa·m<sup>1/2</sup>), outperforming all reported binary alumina-based counterparts. The property synergy originated from a cascaded strengthening mechanism that spanned atomic-scale lattice distortion to nanoscale coherent interfaces, coupled with multi-mode toughening via crack deflection, bifurcation, and bridging. Our work establishes a high-entropy eutectic design strategy for engineering ceramics with exceptional mechanical performance under extreme conditions.