Synthesis of spherical Si3N4 powders by liquid-phase modified carbothermal reduction and nitridation

β-Si 3 N 4 powder with well-dispersed spherical particles was synthesized by liquid-phase modified carbothermal reduction and nitridation. The influence of the type and content of additives on the particle morphology was investigated. The liquid phase formed at the reaction temperature modifies the morphology of the Si 3 N 4 powder. The Si 3 N 4 products precipitated along the liquid-solid interface, thus forming a spherical morphology and promoting the transformation from α-Si 3 N 4 to β-Si 3 N 4 . The type of additives has a strong influence on the formation temperature and viscosity of the liquid phase and hence affects the product morphology. In the samples with CaF 2 and CaO additives, sufficient liquid phase occurred and spherical particles were obtained. In the sample with Y 2 O 3 , however, the liquid phase was insufficient due to the higher formation temperature, thus resulting in an irregular particle morphology.