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The self-reinforced Si_3N_4 ceramics which contain Y_2O_3 and La_2O_3 additives have beenprepared by hot-pressing. Under the optimum processing conditions, this material has theflexural strength of 960～1050MPa and the fracture toughness of 11.17～12.74MPa·m~(1/2) atroom-temperature, and 720～780MPa and 22～24MPa·m~(1/2) at 1350℃. The effects of heating rate, sintering temperature, and holding time on the microstructures and mechanical properties are investigated. The experimental results show that an appropriate β-Si_3N_4 grainsize and homogeneous microstructure can be obtained under the conditions of a heating rate of 10℃/min, sintering temperature of 1800℃, and holding time of 1h, which are advantageous to enhancing the mechanical properties. Crack deflection in large rodlike β-Si_3N_4 grains is a principle source of toughening.
Under the optimum processing conditions, this material has the flexural strength of 960 ~ 1050MPa and the fracture toughness of 11.17 ~ 12.74MPa · m ~ (1/2). The self-reinforced Si_3N_4 ceramics which contain Y_2O_3 and La_2O_3 additives have beenprepared by hot- ) atroom-temperature, and 720 to 780 MPa and 22 to 24 MPa · m ~ (1/2) at 1350 ° C. The effects of heating rate, sintering temperature, and holding time on the microstructures and mechanical properties are investigated. The experimental results show that an appropriate β-Si_3N_4 grainsize and homogeneous microstructure can be obtained under the conditions of a heating rate of 10 ° C / min, sintering temperature of 1800 ° C, and holding time of 1h, which are advantageous to enhance the mechanical properties. Crack deflection in large rodlike β-Si_3N_4 grains is a principle source of toughening.