Spark Plasma Sintering of Nanosized Amorphous Silicon Nitride Powder with a Small Amount of Sintering Additive

Dense and fine‐grained β‐Si 3 N 4 ceramics were successfully obtained with a small amount of sintering additives, 1.5 mass% Y 2 O 3 and 0.5 mass% Al 2 O 3 , using nanosized amorphous Si 3 N 4 powder by spark plasma sintering at temperatures of 1500°–1800°C and a pressure of 30 MPa under N 2 . The β‐Si 3 N 4 ceramics were composed of equiaxed grains with an average size of 300 nm. A higher sintering temperature was required for the densification of submicrometer‐sized α‐Si 3 N 4 powder with the small amount of the additives. The use of nanosized amorphous Si 3 N 4 powder accelerated the densification and the transformation to the β‐phase.