Effect of Sintering Temperature and Yttrium Composition on the Densification, Microstructure and Mechanical Properties of Spark Plasma Sintered Silicon Nitride Ceramics with Al₂O₃ and Y₂O₃ Additives

Three types of silicon nitride ceramics powder blends were sintered by spark plasma sintering at different temperatures and pressures. The relative densities, microstructures, hardness and toughness of the material were investigated with the sintering behaviour. It was observed that the relative density depends on the sintering temperature, the sintering pressure and the yttrium composition. The densification of the sintered ceramics increased with increasing sintering temperature, application of step pressure and yttrium composition, facilitating necking of grains. This in turn affected the microstructure and the mechanical properties of the materials in a manner that the highly dense material induced full compacted particle deformation observed in the microstructures and also high mechanical properties of as high as 1841 HV and 8,87 MPa·√m with the relative density of 99%.