Relationship between microstructure and mechanical performance of a 70% silicon nitride-30% barium aluminum silicate self-reinforced ceramic composite

The abnormal grain growth of beta -Si(3)N(4) was observed in a 70% Si(3)N(4)-30% barium aluminum silicate (70%-Si(3)N(4)-30%-BAS) self-reinforced composite that was pressureless-sintered at 1930 degreesC; Si(3)N(4) starting powders with a wide particle-size distribution were used. The addition of coarse Si(3)N(4) powder encouraged the abnormal growth of beta -Si(3)N(4) grains, which allowed microstructural modification through control of the content and size distribution of beta -Si(3)N(4) nuclei. The mechanical response of different microstructures was characterized in terms of flexural strength, as well as Indentation Fracture resistance, at room temperature. The presence of even a small amount of abnormally grown beta -Si(3)N(4) grains improved the fracture toughness and minimized the variability in flexural strength.