Influence of sintering aids on properties of dense Si2N2O ceramic developed by spark plasma sintering

Through reactive liquid phase sintering, dense and homogenous pellets with a diameter of 40 mm were successfully achieved after 50 min. These samples contain at least 95 vol% of Si2N2O. The microstructure, fracture toughness, coefficient of thermal expansion (673-1673 K), dielectric properties and high-temperature oxidation resistance were investigated to determine the influence of sintering aids such as lanthanide oxides (Sm2O3 and Y2O3) and metal oxide (Al2O3). The nano-sized grains generated have a uniform distribution. The composition of the sintering aid has no influence on the coefficient of thermal expansion or the dielectric properties. The crack propagation mode shifts from transgranular to intergranular in Al2O3 samples, which increases the fracture toughness. The lanthanide oxide samples, on the other hand, outperform the Al2O3 samples in terms of oxidation resistance, as a protective SiO2 and Ln2Si2O7 layer forms on the surface of the oxidized samples.