Carbothermal Synthesis of Silicon Nitride: Effect of Reaction Conditions

Conditions for carbothermal synthesis of α‐Si 3 N 4 are presented with special emphasis on the reaction temperature, C:SiO 2 ratio, and precursor mixing. With pure precursors, the conversion temperature is 1500° to 1550°C. An excess of C is necessary for complete conversion, and a simple sol–gelmixing technique provides excellent intermixing of the precursors. Copious flow of N 2 gas throughout the reactor bed is essential if pure Si 3 N 4 is to be produced; small concentrations of CO and O 2 promote SiC and Si 2 N 2 O, respectively.