The densification of Si3N4 ceramics using different additives via microwave sintering

Abstract

Silicon nitride ceramics were fabricated via 2.45GHz microwave sintering at different systems which included Si3N4-Y2O3-Al2O3 system, Si3N4-Y2O3-Al2O3-ZrO2 system and Si3N4-Y2O3-Al2O3-ZrO2-Li2CO3 system. The system of Si3N4-Y2O3-Al2O3-ZrO2-Li2CO3 exhibited preferable properties which had completely phase transformation, Vickers hardness of 12 GPa and the flexure strength of 400MPa at a lower temperature of 1550°C. The results also showed that ZrO2 had good ability in absorbing microwave and Li2CO3 could promote the densification. Scanning microscopy micrographs revealed the phenomenon of crack deflection, debonding and pull-out of β-Si3N4 grains.