Oxide ion conductors based on niobium-doped bismuth vanadate: conductivity and phase transition features

Oxide ion conductors are technologically important materials, essential for electrochemical devices such as oxygen separation membranes and solid oxide fuel cells (SOFCs). Bi4V2 -aEuro parts per thousand x Me (x) O11 -aEuro parts per thousand delta (BiMeVOx) is a well-known family of material with high ionic conductivity at low operating temperatures. However, it is often reported to possess three structurally related phase changes that affect the vacancy order/disorder over the oxygen atom positions. This might be overcome by a careful chemical design of an oxide ion conductor by introducing the stabilizing dopants. Here, it is found that niobium (Nb) doping on the V site can increase the stability (tetragonal structure) and ionic conductivity at a temperature range of 200-600 A degrees C. This study demonstrates the effect of the doping amount on the ionic conductivity and characterizes the obtained materials by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analyses. The oxidation state of vanadium that related to the electronic structure of BiMeVOx is investigated by X-ray photoelectron spectroscopy (XPS) analysis. It is expected to understand the conductivity and phase transition features of this kind of oxide ion conductor.