High Strength ‐ Toughness Hexagonal Boron Nitride Ceramics with Continuous Interface Structure

ABSTRACT Hexagonal boron nitride ( h ‐BN) ceramics are attractive candidates for both structural and functional applications. However, the challenges in their inadequate deformability and inherent brittleness have not been significantly addressed. Herein, a type of h ‐BN ceramics (M2B‐700‐1300) with combined superior strength and toughness is fabricated via pre‐pyrolysis, pressure molding, and high‐temperature sintering in sequence. The key to the proposed strategy lies in proactively completing the intense gas‐phase reaction of the precursor during the pre‐pyrolysis stage, thereby forming a homogeneous boron oxynitride intermediate phase and then effectively alleviating structural collapse and pore defects during high‐temperature sintering. The resulting ceramics, with densely stacked nanosheets framework bond‐bridged by amorphous boron oxynitride structure, exhibit robust compressive strength of 439.2 MPa and large deformation of 10.18%. Impressively, it is as high as 5‐8 times that of general h ‐BN ceramics in stress, and far exceeds 4% of traditional ceramics for strain, respectively. The successful synthesis of h ‐BN bulk ceramics with both superior strength and toughness provides potential opportunities for fabrication of other high deformability ceramics.