Wadsley vanadium oxides

Abstract

Wadsley vanadium oxides form a homologous series V_nO_2n+1 between the end members α-V₂O₅ and VO₂(B). They exhibit a variety of crystal structures due to different polyhedra around the V⁴⁺ and V⁵⁺ cations and polyhedral connectivity. Their structural features as well as transport and magnetic properties are reviewed here. The Wadsley vanadium oxides are oxygen deficient with different ordered vacancies in the oxygen cubic close-packing array. The rutile-type structure, with the oxygen hexagonal close packing, is found in V₆O₁₃ (n = 6) obtained at high pressures and high temperatures, which unlike its α polymorph stable at atmospheric conditions, does not undergo a metal-insulator phase transition. This finding opens a possibility of synthesizing new materials with unexpected properties in the system V₂O₅- VO₂ by varying compositions and exerting extreme conditions.