Cross Effect Between Ion and Electron Flows in Fe3–δO4

The effective valence, of mobile cations (Fe2+, Fe3+) in semiconducting Fe3O4 was determined at elevated temperatures via Tubandt-type electrotransport experiments in association with the literature data on the cation diffusivity and total electrical conductivity. It has been found that the value for varies systematically from below 2 up to 3 with oxygen partial pressure at a fixed temperature. The effective valence is determined not only by the mobility difference of Fe2+ and Fe3+ ions but also by the cross effect between the cations and electrons upon their transfer . A value of between 2 and 3 may be attributed to the mobility difference between Fe2+ and Fe3+ ions even in the absence of the cross effect, but the values of < 2 clearly indicate that the cross effect is in play in Fe3O4.