Development of calcium stabilized nitrogen rich α-sialon ceramics along the Si_(3)N_(4):1/2Ca_(3)N_(2):3AlN line using spark plasma sintering

Calcium stabilized nitrogen rich sialon ceramics having a general formula of Ca_(x)Si_(12-2x)Al_(2x)N_(16) with x value(x is the solubility of cation Ca in α-sialon structure)in the range of 0.2-2.2 for compositions lying along the Si_(3)N_(4):1/2Ca_(3)N_(2):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℃(typically reported a temperature of 1700℃ or greater)remains to be the highlight of the present study.The SPS processed sialons were characterized for their microstructure,phase and compositional analysis,and physical and mechanical properties.Furthermore,a correlation was developed between the lattice parameters and the content(x)of the alkaline metal cation in the α-sialon phase.Well-densified single-phase nitrogen rich α-sialon ceramics were achieved in the range of 0.53(3)≤x≤1.27(3).A nitrogen richα-sialon sample possessing a maximum hardness of 22.4 GPa and fracture toughness of 6.1 MPa·m^(1/2) was developed.