Effects of sintering aids on mechanical and dielectric properties of Si3N4 ceramics

Abstract

Si3N4 ceramics with different sintering aids are prepared by gas pressure sintering at 1800°C under 8 MPa N2 atmosphere. The mechanical and microwave dielectric properties of the Si3N4 ceramics with and without sintering aids are investigated. The results show that the sintering aids have a significant impact on the densification and mechanical properties of Si3N4 ceramics. Of all, the Si3N4 ceramics using the dry gel of yttrium aluminium garnet as sintering aids exhibit the maximum bending strength and fracture toughness, reaching 395 MPa and 4·25 MPa m1/2 respectively. However, the dielectric properties of Si3N4 ceramics are similar to that using the other two sintering aids. The improved mechanical properties of the Si3N4 ceramics are attributed to the formation of rod-like βSi3N4-particles.