Materials Transactions, Vol.49 No.08 (2008) pp.1926-1928
© 2008 The Japan Institute of Metals

Microstructural Evolution and Pressure-Assisted Master Sintering Surface of Silicon Nitride

Kyong Jun An, Hyun Jong Kim and Myung Keun Han

The pressure-assisted master sintering surface (PMSS) of silicon nitride has been constructed, in which the sintered density during hot pressing can be predicted as a function of the integral of a temperature function over time at a given pressure, irrespective of the heating path. High-purity α-Si₃N₄ powder with the additives of 6.25% Y₂O₃ and 1% Al₂O₃ was used for this research. Densifications of silicon nitride were continuously recorded during heating at two different ramping rates of 0.083°C/s and 0.167°C/s up to 1800°C at fixed pressures from 7 to 34 MPa. The activation energy was estimated as 698 kJ/mol. During the hot pressing, the microstructural evolution of α-Si₃N₄ to β-phase known as a solid/liquid/solid mechanism was also observed. Using the PMSS of silicon nitride, the final density can be predicted to about 1% accuracy for a fixed pressure and an arbitrary temperature-time path.

(Received 2008/1/18; Accepted 2008/6/3; Published 2008/7/16)

Keywords: silicon nitride, pressure-assisted master sintering surface, activation energy, hot pressing

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