The cation distributions in the spinel phases of the mixed vanadium oxides LiZnx V2‐xO4 and LiMgx V2‐xO4

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Abstract
Cation distributions and values of the oxygen parameter in the spinel phases of mixed vanadium oxides with the general formula LixMeV2–xO4, where Me is Zn or Mg, respectively, were studied by X‐ray diffraction measurements. The distribution of cations on the sublattices in the zinc series can be expressed by the formula Li1–x–δ Znx Vδ [Lix+δ V2–x‐δ] and for the magnesium series by the formula Li1–δ Vδ [Liδ Mgx V2–x‐δ]. For the zinc series a general uniform increase of the oxygen parameter was determined. The substitution of magnesium ions leads to an anomal course of this parameter, which is possible to explain by substitution of magnesium ions on intersticial sites. The results are discussed using the values of the Madelung energy. The recently observed tetragonal deformation of the spinel lattice for the bulk composition Li Mg0.375 V1.625 O4 is explained by a cooperative Jahn Teller effect of V4+ ions.