Fabrication of Dense β-SiAlON Ceramics with ZrO2 Additions Via a Rapid Reaction-Bonding and Postsintering Route

Rapid nitridation was used to fabricate reaction-bonded and postsintered beta-Si6-ZAlZOZN8-Z (Z=1) ceramics with monoclinic ZrO2 added to the starting powder. Thermo-gravimetric analysis revealed that the addition of ZrO2 reduced the starting temperature of the main nitridation reaction. Using a reaction-bonding route with heating rates of 5 degrees, 10 degrees, and 20 degrees C/min, to fabricate beta-SiAlON ceramics without ZrO2 resulted in unreacted silicon that bled out of the specimens and the Z=1 composition samples did not maintain the original green compact morphology. On the other hand, no such bleeding of melted silicon was observed for samples with ZrO2 additions and the samples following nitridation maintained the original green morphology. The microstructure and mechanical properties of samples produced by rapid reaction bonding and postsintering were comparable to those of samples produced by a conventional reaction-bonding and postsintering route.