Influence of Yttria–Alumina Content on Sintering Behavior and Microstructure of Silicon Nitride Ceramics

The present study investigates the influence of the content of Y 2 O 3 –Al 2 O 3 sintering additive on the sintering behavior and microstructure of Si 3 N 4 ceramics. The Y 2 O 3 :Al 2 O 3 ratio was fixed at 5:2, and sintering was conducted at temperatures of 1300°–1900°C. Increased sintering‐additive content enhanced densification via particle rearrangement; however, phase transformation and grain growth were unaffected by additive content. After phase transformation was almost complete, a substantial decrease in density was identified, which resulted from the impingement of rodlike β‐Si 3 N 4 grain growth. Phase transformation and grain growth were concluded to occur through a solution–reprecipitation mechanism that was controlled by the interfacial reaction.