The densification of silicon nitride powder by pulsed electric current sintering was investigated to fabricate fine-grained ceramics. Alpha-type sub-micrometre powder (designated A), P-type sub-micrometre powder (B), and P-type fine powder (BF) were sintered with 5 wt% Y2O3 and 2 wt% MgO at 1580degreesC for 5 minutes. Average heating rate from room temperature to the sintering temperature was about 300 Kminute(-1). Dense ceramic was obtained from powder BF, but bulk densities of the ceramics formed from powders A and B were less than 90%. The effect of atmosphere, duration, and temperature was investigated for sintering powder BE Powder BF was densified up to 98.5% at 1550degreesC for 8.5 minutes in vacuum, but, in Ar, the density was 85.5% at 1550degreesC for 10.5 minutes. Powder BF was heated up to 1450degreesC, held for 5 minutes, and then heated to 1550degreesC. Densification was completed in 3 minutes, even in an Ar atmosphere.

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