Development of calcium stabilized nitrogen rich alpha-sialon ceramics along the Si3N4:1/2Ca3N2:3AlN line using spark plasma sintering

Abstract Calcium stabilized nitrogen rich sialon ceramics having a general formula of CaxSi12-2xAl2xN16 with x value in the range of 0.2-2.2 for compositions lying along the Si3N4:1/2Ca3N2:3AlN line were synthesized using nano/submicron size starting powder precursors and spark plasma sintering (SPS) technique. The development of calcium stabilized nitrogen rich sialon ceramics at a significantly low sintering temperature of 1500°C (typically reported a temperature of 1700°C or greater) remains to be the highlight of the present study. The SPS processed sialons were characterized for their microstructure, phase and compositional analysis, physical and mechanical properties. Furthermore, a correlation was developed between the lattice parameters and the content (x) of the alkaline metal cation in the alpha-sialon phase. Well densified single-phase nitrogen rich alpha-sialon ceramics were achieved in the range of 0.53(3) ≤ x ≤ 1.27(3). A nitrogen rich alpha-sialon sample possessing a maximum hardness of 22.4 GPa and fracture toughness of 6.1 MPa.m1/2 was developed.