First-principles study on the interfacial interactions between h-BN and Si3N4

Abstract High-performance ceramics, especially h-BN-based ceramics, are widely used in the metallurgical field. The interface state of h-BN-based ceramic composites, including chemical reactions, molecular diffusion, and interface structure changes, will greatly affect the properties of composite materials. Herein, taking Si 3 N 4 /BN composites as a representative case, their interfacial interactions were investigated by first-principles calculations. First, the structural and electronic properties and elastic modulus of bulk Si 3 N 4 and h-BN were calculated. Then, the interface mismatch relationship and interface models of Si 3 N 4 /BN were studied and established. Finally, the interface bond structure of Si 3 N 4 /BN was analyzed by charge density and state density calculations. The results showed that the band gap of bulk Si 3 N 4 and h-BN was 4.18 and 4.24 eV, respectively. Besides, bulk h-BN exhibited better compression performance and resistance to deformation than Si 3 N 4 based on elastic modulus calculation. Therefore, h-BN was used as a substrate, and when interface mismatch is 1.3%, good matching and bonding at the interface layer can be obtained. Based on this, two interface models of Si 3 N 4 (100)/BN(002) were established, which were named the B-N Si interface and Si-N B interface. The BN/Si 3 N₄ interface exhibited strong van der Waals interactions, and the charge transfer from Si 3 N 4 to h-BN was observed, which indicate that the weak covalent bond also exists in the BN/Si 3 N 4 interface. The low interface energy indicates that the formed interface is relatively stable, which is beneficial for applications requiring high thermal and mechanical stability. This work provides valuable insights into the interfacial interaction between h-BN and Si 3 N 4 and will give a promising theoretical guidance for designing and optimizing h-BN-based ceramic composites.