Solid‐state reactions of equimolar mixtures of Bi2O3and Fe2O3from 625° to 830°C and their kinetics were investigated. The reaction rates were determined from the integrated X‐ray diffraction intensities of the strongest peaks of the reactants and products. The activation energy for the formation of BiFeO3was 96.6±9.0 kcal/mol; that for a second‐phase compound, Bi2Fe4O9, which formed above 675°C, was 99.4±9.0 kcal/mol. Specific rate constants for these simultaneous reactions were obtained. The preparation of single‐phase BiFeO3from the stoichiometric mixture of Bi2O3and Fe2O3