IMF2017

BiFeO₃ is a multiferroic magnetoelectric material with a rhomboedrally distorted perovskite structure (R3c space group) presenting ferroelectric and antiferromagnetic (G-type) ordering at room temperature with elevated Curie (TC ~ 1103 K) and Néel (TN ~ 643 K) temperatures. However, the formation of undesired phases in polycrystalline BiFeO₃, mainly Bi₂₅FeO₃₉ and Bi₂Fe₄O₉ turns the preparation of high resistive single-phased BiFeO3 ceramics a challenge. In this work, high-energy ball milling allied to fast sintering were applied to achieve phase-pure nanostructured powders and Spark-Plasma Sintering (SPS) was used to synthesize nanostructured BiFeO₃ monolithic samples. Single-phased BiFeO₃ powder were obtained by the milling process and exhibited a mean size around 150 nm and SPS resulted in highly dense monoliths samples. However, X-Ray Diffraction (XRD) evidenced the presence of secondary phases after SPS process and electric measurements revealed low electrical resistivity. A thermal treatment under oxygen positive pressure (60 psi) were used to promote sample re-oxidation and impedance spectroscopy confirmed an enhanced resistivity after 96 h treatment. Vibrating Sample Magnetometry (VSM) measurement shows magnetization around 3,5 emu/g after oxygen annealing and microstructural analyses by electron scanning microscopy (SEM) reveals no grain growth after SPS as well as after oxygen annealing.