Structural Refinement of a-Bi₄V₂O_11-x (x=0, 0.33) using high-resolution electron microscopy

alpha-Bi4V2O11 and Bi6V3O16 have been prepared by solid state reaction and their structural chemistry has been investigated using X-ray powder diffraction, high-resolution electron microscopy, solid-state nuclear magnetic resonance and electron-energy-loss spectroscopy. Their structures are closely related to each other and are both derived from gamma-Bi4V2O11 With Bi2O2 layers partially depressed in an ordered manner, forming various superstructures and implying a location of oxygen vacancies in the Bi2O2 layers, rather than the V-O layers as previously believed. These results necessitate a reconsideration of the mechanism of ionic conductivity in these materials.