Dense and fine-grained β-Si3N4 ceramics were successfully obtained with a small amount of sintering additives, 1.5 mass% Y2O3 and 0.5 mass% Al2O3, using nanosized amorphous Si3N4 powder by spark plasma sintering at temperatures of 1500°-1800°C and a pressure of 30 MPa under N 2. The β-Si3N4 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 3N4 powder with the small amount of the additives. The use of nanosized amorphous Si3N4 powder accelerated the densification and the transformation to the β-phase.
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