The effect of Fe²⁺ state in electrical property variations of Sn-doped hematite powders

The structural, electrical, and chemical properties of Sn-doped Fe₂O₃ powders were investigated. Various quantities of Sn-doped Fe₂O₃ powders were synthesized using solid-state reactions. Rietveld analysis for the powders that were doped below 2% revealed a phase-pure Sn-doped Fe₂O₃ structure (i.e., identical to Fe₂O₃ structure). Alternatively, the analysis for the powders that were doped more than 3% exhibited secondary phase. The unit cell volume and electrical conductivity of the phase-pure samples increased with an increase in the doping concentration. X-ray photoelectron spectroscopy measurements showed an increased Fe²⁺ state with the increase in Sn doping concentration. Therefore, the improved electrical conductivity and unit cell volume with the increase in doping concentration of the phase-pure powders might be related to the increased Fe²⁺ state.