Tough and strong bioinspired high-entropy all-ceramics with a contiguous network structure

Developing bioinspired all-ceramics with plastic phases is considered one of the most effective ways to simultaneously achieve enhanced strength and toughness in ceramic materials for high-temperature applications. Here we explore tough and strong bioinspired high-entropy all-ceramics with a contiguous network structure that are able to serve up to 1300 °C. Specifically, we develop the high-entropy all-ceramics, featuring a unique contiguous network distribution of the Cr7C3 plastic phase within the predominant high-entropy carbide (HEC) hard phase, through a high-entropy composition-engineering strategy. The resulting materials exhibit impressive fracture initiation toughness of 12.5 ± 1.5 MPa·m1/2 and flexural strength of 613 ± 52 MPa at room temperature, as well as ~97% strength retention up to 1300 °C due to their good high-temperature stability, surpassing the performance of most other reported bioinspired ceramics. Further experimental and theoretical investigations demonstrate that the Cr7C3 phase can undergo plastic deformation by forming nanoscale shear bands with significant crystal defects, resulting in multiple toughening mechanisms involving crack-bridging of unfractured Cr7C3 ligaments and crack deflection in the HEC/Cr7C3 all-ceramics. This work successfully develops tough and strong bioinspired high-entropy all-ceramics capable of serving up to 1300 °C, offering an innovative strategy that facilitates further design of bioinspired ceramics applicable at higher temperatures.