Synthesis of spherical Si₃N₄ Powders by liquid‐phase modified carbothermal reduction and nitridation

Abstract

β‐Si₃N₄ 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 Si₃N₄ powder. The Si₃N₄ products precipitated along the liquid‐solid interface, thus forming a spherical morphology and promoting the transformation from α‐Si₃N₄ to β‐Si₃N₄. 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 CaF₂ and CaO additives, sufficient liquid phase occurred and spherical particles were obtained. In the sample with Y₂O₃, however, the liquid phase was insufficient due to the higher formation temperature, thus resulting in an irregular particle morphology.

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