From Bi4V2O11 to Bi4V2O10.66: the VV–VIV transformation in the aurivillius-type framework

Abstract

Bi₄V₂O₁₁, the parent compound of the BIMEVOX family, has been studied by TEM and HREM, at room temperature and at high temperatures. Under the experimental conditions, Bi₄V₂O₁₁ undergoes a V^V–V^IV reduction, ultimately leading to the formation of Bi₆V₃O₁₆(Bi₄V₂O_10.66) with V^IV/V^V= 1/2. This transformation is confirmed by in situ X-ray diffraction studies of Bi₄V₂O₁₁ under reducing atmospheres up to 330 °C. The symmetry of the α-Bi₄V₂O₁₁ polymorph, stable at ambient temperature, is dependent on the chemical purity of V₂O₅ used for the synthesis.