Effect of processing parameters on densification and mechanical properties of gas-pressure sintered silicon nitride

Silicon nitride containing a variety of additives was densified using gas pressure sintering (GPS). The packing powder composition, crucible type, sintering temperature, nitrogen pressure, sintering time, use of barrier/protective coatings, and setter type were shown to affect the sintering behavior. Optimum conditions for densification, minimization of weight loss and minimization of reaction layer thickness were dependent on the sample composition. During high temperature GPS processing, chemical and physical gradients developed from the exposed surfaces to the interior regions. Along with the compositional gradients, mechanical property differences also exist between the as-sintered surfaces and the bulk materials.