Sol–gel synthesis and properties of multiferroic BiFeO3

High purity multiferroic BiFeO3 (BFO) powders were synthesized by sol–gel process using bismuth nitrate and iron nitrate as sources. The BFO powders annealed at 600 °C in nitrogen environment were mainly composed of a rhombohedral BiFeO3 phase (R-phase) with a minor impurity phase of Bi2O3. A pure BFO R-phase has been obtained by leaching out the minor Bi2O3 phase using diluted nitric acid. A reversible phase transformation of the BFO R-phase has been detected at 836 °C by a differential thermal analysis. The powders of BFO R-phase exhibits a uniform feature with the particle size of ∼200 nm. The dielectric constant of the BFO R-phase is measured to be ∼15 in the frequency range of 104∼106 Hz at room temperature.