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Verteilung und Valenz der Kationen in Spinellsystemen mit Eisen und Vanadium, VIII

Riedel, Erwin; Kähler, Jörg; Pfeil, Norbert

FG Anorganische Chemie - Festkörper- und Materialchemie

From lattice constants and Mössbauer data the valence distribution and an energy-level diagram of the spinel system Fe(FexV2-x)O4 have been derived. In the range 0.3 ≦ χ ≦ 1.5 the transition from normal to inverse spinels takes place. The Mößbauer spectra with 1.0 ≦ χ ≦ 2.0 consist of two sets of sextets corresponding to tetrahedral and octahedral sites. Typical values of isomer shift and internal magnetic field strength due to the different environments of the iron ion result from the superimposed sextets of the octahedral site pattern. Neighbouring V ions enhance the conduction electron density and diminish the strength of the magnetic interaction. Mößbauer data, Seebeck coefficients and activation energies lead to a model of both tetrahedral and octahedral conduction based on charge hopping. For Fe1,9V1,1 O4 there exists only one iron species.