Formation behavior and equilibrium thermodynamics study on the Bi₂O₃-Fe₂O₃ system for synthesis of the bismuth ferrites

The bismuth ferrites are significant materials due to their unique multifunctional properties and broad applications. However, a lack of fundamental understanding of their formation behavior and thermodynamics constrains the reliable prediction of synthesis pathways and final properties. This work synthesized Bi₂₅FeO₃₉, BiFeO₃ and Bi₂Fe₄O₉, characterizing them via in-situ X-ray diffraction, scanning electron microscopy, high temperature differential scanning calorimetry and high temperature oxide melt solution calorimetry. Based on the experimental data obtained in this work and from the literature, a thermodynamic description of the Bi₂O₃–Fe₂O₃ system was carried out. The thermodynamic database along with the calculated phase diagram and thermodynamic properties of the system were provided. Comparison between the present calculation with the experimental data was provided and discussed.