Silicon nitride having a high tensile strength

A process for producing a high tensile strength silicon nitride ceramic, comprising the steps of:

• a) milling a batch of silicon nitride powder in water to produce a slurry,
• b) passing the slurry through a filter having a pore size of between about 2 and about 10 microns,
• c) concentrating the slurry to a solids content of between about 70 and about 72 w/o,
• d) passing the slurry through a magnetic separator,
• e) casting the slurry at a CRS rate of less than about 10 mm.sup.2 /min to produce a green body comprising at least about 80 w/o silicon nitride,
• f) drying the green body to less than about 3 w/o water,
• g) degassing the green body,
• h) sintering the green body to yield a dense ceramic comprising at least about 80 w/o silicon nitride,
• i) machining the dense ceramic, and
• j) heat treating the dense ceramic to yield a high tensile strength silicon nitride ceramic.