Mechanically assisted synthesis of multiferroic BiFeO₃: Effect of synthesis parameters

We report the influence of synthesis parameters on the crystal structure and the electronic and magnetic behavior of multiferroic bismuth ferrites, BiFeO₃, synthesized by high-energy ball milling followed by annealing at low temperatures. Mixtures of Fe₂O₃ and Bi₂O₃, in a stoichiometric ratio, were mixed and milled for different durations from 0 to 13 h in an ambient air atmosphere and annealed for 2 h at different temperatures, from 350 to 750 °C in order to obtain BiFeO₃. X-ray diffraction and Rietveld refinement were used to elucidate the phase transformation as a function of the synthesis parameters. The results showed that BiFeO₃ particles with mostly a single phase (∼98 wt%) were fabricated by the assisted high-energy ball milling process, after 5 h of milling followed by heat treatment at 650 °C; higher milling durations and annealing temperatures promote perovskite decomposition. The obtained powder shows a weak ferromagnetic behavior, which changes to an antiferromagnetic order when the powder is pressed at 900 MPa and sintered at 800 °C for 2h. The magnetic and dielectric results confirm the multiferroic behavior of the obtained material.