BiFeO3 has been synthesized from the nitrate salts of bismuth and iron at different temperatures at 500, 600 and 700 °C. The time–temperature-transformation (TTT) has been analysed at the annealing time duration of 1, 2, 3, 4, 5, 6 and 7 h. Thermo-gravimetric study of the starting solid has been analysed from room temperature to 800 °C and the reaction kinetics have been investigated from 400 to 700 °C using Flynn-Wall-Ozawa model which has also been correlated with the differential thermal analysis (DTA). Gibbs free energies of the formation of BiFeO3, Bi2Fe4O9 and Bi25FeO39 have been calculated to investigate the reason for the maximum percentage of pure BiFeO3 phase formation at 600 °C. Based on the calculation, though later two compounds are thermodynamically destabilizing secondary phases of BiFeO3, its synergetic stabilization has been supported by the diffusion kinetics and their activation energies. © 2020