Structural, ferroelectric and magnetic properties of BiFeO3 synthesized by sonochemically assisted hydrothermal and hydro-evaporation chemical methods

BiFeO3 powders were synthesized by sonochemically assisted hydrothermal and hydro-evaporation methods. The X-ray diffraction confirmed the presence of secondary phases, Bi25FeO39 and Bi2Fe4O9, in as prepared BiFeO3 powders. Optimization of sintering conditions indicated that temperature of 800 °C and time of 2 h after pressing at 9 t/cm2 provided ceramics samples with the highest density (up to 96% of theoretical density) and the lowest content of secondary phases. Ferroelectric and magnetic characterization was performed on two selected ceramics samples with the highest densities. Ceramics obtained from the powder synthesized by the hydrothermal method showed greater lattice distortion along [1 1 1] axis and smaller grains, which resulted in larger values of electric polarization at room temperature. It also exhibited less Fe(3d)-O(2p) orbital overlapping due to a larger FeOFe bond angle, causing lower antiferromagnetic ordering and weak ferromagnetic behavior at low temperatures.