Abstract
Dense α-Si3N4 ceramics were fabricated by the tape casting technique using La2O3 as a sintering additive to effectively suppress the α-β transformation. Addition of a small amount of elongated β-Si3N4 seed particles significantly improved the toughness of sintered bodies from about 2 to 6MPa·m1/2. It was found that both strength and toughness showed a linear dependence on the β-Si3N4 content, while hardness remained almost constant up to a β-content of 43%. Consequently, it was possible to fabricate the α/β-Si3N4 composites that showed much higher hardness (about 19GPa) than ordinary Si3N4 and SiAlON ceramics, as well as comparable strength (about 800MPa) and toughness (about 6Pa·m1/2).
