Studies of potassium ferrite K1+xFe11O17. I. Electronic conductivity and defect structure

• Published in: Journal of solid state chemistry Vol. 18; no. 2; pp. 141 - 147
• Main Authors: Dudley, Geoffrey J., Steele, Brian C.H., Howe, Arthur T.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.06.1976
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/0022-4596(76)90088-8

The electronic conductivity of the nonstoichiometric potassium ferrite phase (with the β-alumina structure) has been measured as a function of temperature and potassium ion concentration. The latter was varied by coulometric titration using the cell: K11q/K-β-alumina/K1+xFe11O17. At 523°K the conductivity increased nearly linearly as x was increased from 0.09 to 0.65 while the activation energy for conduction decreased from 0.1 to 0.07 eV. The cell emf was completely reversible. The results are consistent with the view that the excess potassium ions are charge compensated by reduction of Fe3+ to Fe2+, and a comparison with results in the literature for some ironcontaining spinels suggests that a similar small polaron electron hopping mechanism operates.