Electrical Properties of Stoichiometric BiFeO3 Prepared by Mechanosynthesis with Either Conventional or Spark Plasma Sintering

Phase-pure powders of stoichiometric BiFeO3 have been prepared by mechanosynthesis. Ceramics sintered by either conventional heating in air or spark plasma sintering (SPS) followed by oxidative anneal in air are highly insulating at room temperature with resistivity, extrapolated from the Arrhenius plots, of similar to 1016cm and activation energy 1.15(2)eV, comparable with those of a good-quality BiFeO3 single crystal. By contrast, the as-prepared SPS sample without the postsinter anneal shows lower resistivity, e.g., similar to 1010cm at 25 degrees C and activation energy 0.67(3)eV, indicating some reduction in the sample by the SPS process. The reason for the high conductivity reported for some ceramic samples in the literature remains unclear at present.