Direct‐Current Conductivity and Iron Tracer Diffusion in Hematite at High Temperatures

The dc conductivity of natural single‐crystal α‐Fe₂O₃ was measured as a function of O partial pressure from 10⁻⁴ to 1 atm at 950° to 1422°C. The conductivity was independent of O₂ partial pressure, indicating that hematite is an intrinsic semiconductor with lattice defect concentrations much lower than the concentration of intrinsic electrons (holes). The activation energy of the dc conductivity was 1.18 eV. The iron tracer (⁵⁵Fe) diffusion coefficients, measured as a function of O₂ partial pressure at 1200° and 1300°C, increased as the O₂ partial pressure decreased, with a pressure dependence of ‐0.75; the iron therefore migrates interstitially.