Foam structure–derived strong and tough alumina ceramics with fine grains and transgranular fracture

Abstract Controlling the preparation process is essential to ensure the quality of the ceramics. Previous research on the ceramic process concentrated on a certain part of powder synthesis, forming, or sintering. Herein, we propose a novel process, foam precursor–derived Al 2 O 3 ceramics, to realize particle rearrangement, assembly, and sintering and find that this method has a marvelous influence on the microstructure and mechanical properties. Alumina foams prepared by the particle‐stabilized foam method are used as ceramic precursors, and after pre‐sintering, crash, and hot pressing, foam precursor–derived Al 2 O 3 ceramics can be obtained. It has fine grains (1/5 of the traditional process) and uniform grain size without any additional sintering aid, realized by the high grain growth exponent of foams. Ultrahigh dislocation density (∼10 10 mm −2 ) is discovered in (0 0 0 1) plane of foam precursor–derived ceramics, comparable to the dislocation density of high‐entropy ceramics. Besides, transgranular fracture mode is observed in the ceramics prepared by the new method rather than the intergranular fracture in the control group, and the comprehensive mechanical properties are promoted accordingly. The unusual microstructure and fracture mode caused by the foam precursor process reveal the influence of the microstructure such as dislocation and grain boundary on the fracture behavior of ceramics, which is less considered in conventional research. This preparation process may be applied in the preparation of other high‐performance ceramics.