Low temperature fabrication of highly dense α‐Si₃N₄ ceramics

Highly dense α ‐silicon nitride (Si 3 N 4 ) ceramics were densified at a lower temperature of 1450°C under a moderate mechanical pressure of 50 MPa from commercial α ‐Si 3 N 4 powder and with conventional Al 2 O 3 –Y 2 O 3 sintering additives. The fabricated α ‐Si 3 N 4 ceramics exhibited a hardness of 19 GPa, which is higher than that of the β ‐Si 3 N 4 ceramics usually obtained. The effect of sintering temperature and sintering pressure in the liquid phase sintering of the α ‐Si 3 N 4 ceramics is studied. The role of the dissolution–reprecipitation process and the particle rearrangement during densification of the α‐Si 3 N 4 ceramics is discussed.