AbstractSi₃N₄ powders were prepared by combustion synthesis with 1‐ and 3‐μm α‐Si₃N₄, β‐Si₃N₄ 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‐Si₃N₄ and β‐Si₃N₄ as diluents are about 1600–1800°C. Moreover, the newly formed α‐Si₃N₄ contents in the synthesized products with BN as diluent over 90 wt% are much higher than those with α‐Si₃N₄ and β‐Si₃N₄ as diluent about 20–40 wt%. The strip‐like α‐Si₃N₄, rod‐like β‐Si₃N₄ 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 Si₃N₄ is discussed, which provides key guidance for preparing Si₃N₄ powders with high α‐phase content.