Preparation and mechanical behavior of Si3N4 composite ceramics with brick‐and‐mortar structure

Abstract The nacre with brick‐and‐mortar structure enables multiple toughening and strengthening mechanisms, and bioinspired ceramics with brick‐and‐mortar structure have been attracting much attention from many researchers. However, the process of constructing precise and uniform microstructure is quite complicated. Herein, we propose a novel and facial method to fabricate composite ceramics with brick‐and‐mortar structure. Si 3 N 4 microspheres prepared by particle‐stabilized foaming and centrifugal spray drying were directly hot pressed after being immersed in suspension and evenly wrapped with ZrO 2 . The mechanical properties of composite ceramics were optimized by adjusting the pressure during sintering and ZrO 2 content. When ZrO 2 content was 10 wt% and sintering pressure was 5 MPa, the fracture toughness of ZrO 2 /Si 3 N 4 brick‐and‐mortar composite ceramics reached 9.02 MPa·m 1/2 , and the flexural strength was 784 MPa, which were increased by 46.9% and 26.5%, respectively, compared with the control group. While retaining excellent flexural strength, the strong interface also induces crack to deflect and branch along the two‐phase interface of the brick‐and‐mortar structure caused by the residual stress, which was derived from the mismatch of the thermal expansion coefficient of ZrO 2 and Si 3 N 4 , consuming more fracture energy to achieve the toughening effect.