Effects of sintering temperature on the microstructure and properties of h-BN ceramics with MAS as liquid sintering aid

MgO-Al₂O₃-SiO₂ (MAS) glass ceramic was used as liquid sintering aid to densify h-BN ceramics, and effects of sintering temperature on the phase composition of MAS, texture behavior of h-BN grains and properties of the composite ceramics were studied. h-BN grains will react with MAS by forming N-M (Al³⁺ and Si⁴⁺) coordinate-covalent bonds and inhibit the crystallization of glass phase. The h-BN grains will rotate parallel to the pressure direction due to the joint action of the liquid sintering aid and the pressure. The sintering temperature will significantly affect the properties of the composite ceramics by effecting the texture behavior of h-BN grains. And higher sintering temperature of 1900 °C will result in the decline of mechanical properties and increase of thermal conductivity due to the decrease of texture degree caused by the grain growth of h-BN.