Hierarchically Structured Ceramic Coatings Based on Zirconia and Magnesium Oxide with High Toughness

A major challenge in the application of ceramic materials is a trade‐off between strength and toughness. In this work, hierarchically structured ceramic coatings (HSCCs) are fabricated to address this challenge. HSCCs feature a dual‐layer micron‐scale structure built on a “brick‐mortar” nanoscale structure, which is achieved by changing the crystalline and amorphous phase ratio during plasma electrolytic oxidation (PEO). It is found that HSCCs with homogeneous interfaces exhibit high thermal stability up to 700 °C and a 65% improvement in shear strain resistance compared to conventional crystalline coatings (CCCs). This improvement is attributed to the stabilizing effect of atoms on the boundaries of the enhancement phase and the facilitating effect on the deformation of the compliant phase. The hierarchical structure effectively leverages the plasticity of the compliant phase and the strength of the enhancement phase facilitated by the homogeneous interface. This work proposes a feasible approach for improving the toughness of ceramic functional composites and mitigating their susceptibility to brittle fracture.