Synthesis and characterization of the new delafossite-type oxide CuNi1/3V2/3O2

Whereas neither delafossite-type CuIVIIIO2 nor CuINiIIIO2 exist, the authors have succeeded in preparing the delafossite oxide CuINiII1/3VIII1/3VIV1/3O2, using classical solid-state reaction. The most probable formal oxidation state for nickel is II, while for vanadium it is a mixed state +III/+IV. The predominant magnetic interactions are antiferromagnetic, but no evidence could be found for long-range ordering. Charge transport results from a hopping process involving V3+ and V4+ cations. As XRD did not reveal any cation ordering, the observed T-1/4-dependence of the electrical conductivity (Mott's law) is ascribed to a random distribution of the relevant sites.