Impact of environment on the kinetics involved in the solid-state synthesis of bismuth ferrite

Synthesis of bismuth ferrite by a solid-state reaction between Bi₂O₃ and Fe₂O₃ was investigated through thermogravimetry/derivative thermogravimetry/differential thermal analysis (TG/DTG/DTA) technique. The reaction was performed at various heating rates (2, 5, 10 and 15 °C/min) from ambient temperature to 800 °C, in nitrogen and oxygen environments. The main aim was to investigate kinetic parameters and the impact of environment on the reaction. The results obtained from TG/DTG revealed that the reaction occurred in four distinct stages in both environments and substantial conversion was only observed in stage II-III. The activation energy was evaluated for the main stages (stage II-III) in both environments by the Fynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. The trend of activation energy remains identical in both environments. The mechanism involved in the reaction was identified by using the Criado method. It was observed that the reaction mechanism in stage II-III significantly vary with the environment. The magnetization of the BFO sample prepared in nitrogen and oxygen environment was estimated through the Vibrating-sample magnetometer (VSM) at room temperature. The results indicated that nitrogen atmosphere was more suitable for the synthesis of bismuth ferrite with improved magnetization.