Reaction Hot Pressing of α′‐ and β′‐ SiAlON Ceramics

Hot pressing kinetics of α‐Si 3 N 4 , AIN, Al 2 O 3 , and Y 2 O 3 powder mixtures forming α′‐ and β′‐SiAlONs have been studied. Densification proceeds in two steps, first by a small shrinkage upon ternary eutectic oxide melting (SiO 2 –Al 2 O 3 –Y 2 O 3 ) at 1340°C, followed by a massive particle rearrangement and further shrinkage at higher temperature when nitride dissolution begins. With better wettability, AIN initially traps the oxide melt and delays densification. In addition, the preferential dissolution of AIN at 1450°C enriches the melt composition in AI, triggering transient precipitation of supersaturated β′‐SiAlON. Full densification is readily achieved at 1550°C without complete α‐Si 3 N 4 conversion.