This paper reviews the status of a program1 to develop silicon nitride ceramics of high strength and reliability, with the material performance goals being a tensile strength of 900 MPa at room temperature and 500 MPa at 1370°C, both with a Weibull modulus of 20. The selected process consists of injection molding and hot isostatic pressing of a silicon nitride formulation containing 6 w/o yttria as sintering aid. A comprehensive experimental approach has been adopted which consists of: a. complete characterization and subsequent modification of the starting silicon nitride powder in an attempt to correlate powder characteristics to ceramic properties; b. the design and fabrication of appropriate specimens for tensile strength testing; c. the implementation of alternate powder processing and shaping techniques, including the design of new compounding/molding equipment; and d. the expansion of non-destructive evaluation capabilities.

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