Effect of the diluent on combustion synthesis of silicon nitride

Abstract Si ₃ N ₄ powders were prepared by combustion synthesis with 1‐ and 3‐μm α‐Si ₃ N ₄ , β‐Si ₃ N ₄ diluent and BN inert diluent. The maximum temperatures of samples with boron nitride (BN) as a diluent are about 1500–1600°C lower than that of samples with α‐Si ₃ N ₄ and β‐Si ₃ N ₄ as diluents are about 1600–1800°C. Moreover, the newly formed α‐Si ₃ N ₄ contents in the synthesized products with BN as diluent over 90 wt% are much higher than those with α‐Si ₃ N ₄ and β‐Si ₃ N ₄ as diluent about 20–40 wt%. The strip‐like α‐Si ₃ N ₄ , rod‐like β‐Si ₃ N ₄ grains, and radiative shaped grains can be observed in the synthesized products. Finally, the effect of the diluent on the α‐phase content of combustion synthesized Si ₃ N ₄ is discussed, which provides key guidance for preparing Si ₃ N ₄ powders with high α‐phase content.