AUTOCOMBUSTION SYNTHESIS AND CHARACTERIZATION OF MULTIFERROIC BISMUTH FERRITE CERAMICS

Abstract

Bismuth ferrite is one of the most promising single multiferroic materials. It exhibits ferroelectric and antiferromagnetic behavior in wide range of temperatures. Many new applications arise due to possibility of magnetization reorientation by electric field and polarization reorientation by magnetic field [1]. Main problem in usage of BiFeO3 is difficulty of obtaining pure phase ceramic and high conductivity as a result of Fe non-stoichiometry. BiFeO3 (BFO) powders were prepared by auto-combustion and soft chemical methods starting from iron and bismuth nitrates. After the synthesis, fine precursor powders were thermally treated for various periods at different temperatures and heating rates. In case of auto-combustion synthesis, several fuels (citric acid, sucrose and urea) and fuel to oxidizer ratios (F/O) were examined, while for soft chemical synthesis two complexing agents were tested: citric and tartaric acids. Low temperature synthesis was also tested without any complexing agent. XRD measurements showed presence of Bi2O3, Bi2Fe4O9 and Bi25FeO39 secondary phases in all powders, and pure perovskite BFO phase for several sintered samples. Powders and ceramics were characterized by SEM/EDS, TG/DTA, particle size distribution and BET surface area measurements. Impedance and magnetic measurements were performed in order to define electrical and magnetic properties of BFO ceramics.