New process for the preparation of M2+–V2O5–H2O xerogels and their transformation to α-M2+–V2O5 bronzes (M Ca, Mn, Co, Ni, Cu)

Abstract

Five kinds of M²⁺–V₂O₅–H₂O xerogels (M Ca, Mn, Co, Ni, Cu) have been synthesized by a simple aging of V₂O₅ powder in aqueous solutions of MCl₂ below 100 °C. These xerogels had a layer structure with a spacing between 1.20 (for Cu) and 1.38 nm (for Co), larger than the V205 xerogel. The α-M²⁺–V₂O₅ bronzes were obtained by thermal dehydration of the corresponding xerogel at temperatures up to 450 °C. The bronzes synthesized had orthorhombic structure, similar to V₂O₅, and each M²⁺ was located between the ab planes of V₂O₅. The dehydration behaviour and the structural change from xerogel to bronze were also studied.