High entropy oxide as interfacial material for toughened textured alumina

Abstract

AbstractTextured alumina ceramics with brick‐and‐mortar microstructures exhibit surprisingly high values of strength and toughness as compared to traditional ceramics. However, in full ceramic systems, pressure‐assisted sintering restricts their shaping potential, and the study of interfacial materials is still insufficient. Here, we fabricate textured alumina exhibiting elevated indentation fracture toughness using a high entropy oxide (HEO) (MgAlSiTiZr)O as the mortar. The HEO undergoes a single‐phase transformation at 1600°C, resulting in a crystallographic structure identical to that of ZrO2. Our HEO mortar is tough and has a high wetting behavior to alumina platelets used in the green body, which promotes densification via liquid phase sintering. Textured alumina ceramics with HEO mortar at concentrations varying from 0 to 90 wt% were fabricated using magnetically assisted slip casting and pressureless sintering through the templated grain growth process. A trade‐off between density and grain anisotropy led to the highest mechanical properties. Textured alumina with 10 wt% HEO exhibited over 95% relative density, an elastic modulus of 244 ± 29 GPa, a flexural strength of 329 ± 27 MPa, and an indentation fracture toughness of 6.80 ± 0.65 MPa∙m0.5, which is more than 1.9 times that of the usual polycrystalline alumina. Thanks to the mineral nature of HEO, the simplicity of the process, and the mechanical properties, the textured alumina with HEO mortar can be produced in complex shapes and could find applications in stringent environments.