For the spinel system Zn1-ϰFe-λGaϰ-λ(Fe1+λGa1-λ)O4 the index λ has been determined by X-ray measurements: λ = 0 in the region 0 ≤ ϰ ≤ 0,35; the increase of λ to 0,62 within 0,35 ≤ χ ≤ 1 is nearly linear. The distribution of Fe2+ and Fe3+ ions over the lattice sites has been derived from lattice constants and ionic distances, and also by Mössbauer spectroscopy. In the spinels with ϰ < 0,3 the tetrahedral sites are preferably occupied by Fe2+ ions, for x > 0,5 Fe3+ ions dominate. At ϰ = 0,4 the occupation of the lattice sites by iron ions is statistical, the high temperature Mössbauer spectrum shows a single line only. All spinels are n-type hopping conductors mainly conducting via the octahedral sites.
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