From Bi₄V₂O₁₁to Bi₄V₂O_10.66: the V^V–V^IVtransformation 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 VV–VIV reduction, ultimately leading to the formation of Bi6V3O16(Bi4V2O10.66) with VIV/VV= 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.