Low temperature fabrication of highly dense α‐Si3N4 ceramics.

Highly dense α‐silicon nitride (Si3N4) ceramics were densified at a lower temperature of 1450°C under a moderate mechanical pressure of 50 MPa from commercial α‐Si3N4 powder and with conventional Al2O3–Y2O3 sintering additives. The fabricated α‐Si3N4 ceramics exhibited a hardness of 19 GPa, which is higher than that of the β‐Si3N4 ceramics usually obtained. The effect of sintering temperature and sintering pressure in the liquid phase sintering of the α‐Si3N4 ceramics is studied. The role of the dissolution–reprecipitation process and the particle rearrangement during densification of the α‐Si3N4 ceramics is discussed. [ABSTRACT FROM AUTHOR]