Interface structure and formation mechanism of BN/intergranular amorphous phase in pressureless sintered Si3N4/BN composites

The interface structures formed by the BN/intergranular amorphous phase and the Si3N4/intergranular amorphous phase in pressureless sintered Si3N4/hexagonal-BN composites doped with Y2O3 and Al2O3 were investigated by high-resolution transmission electron microscopy. Compared with the direct Si3N4/glass bonding in the Si3N4/amorphous phase interface, an ordered transition layer between hexagonal-BN and the glass phase, including a turbostratic-BN zone and an amorphous-BN zone, was found for the first time. In addition, a chemical reaction mechanism for the formation of BN/amorphous phase interfaces was suggested.