Oxide ion conductors based on niobium-doped bismuth vanadate: conductivity and phase transition features
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Oxide ion conductors are technologically important materials, essential for electrochemical devices such as oxygen separation membranes and solid oxide fuel cells (SOFCs). Bi4V2 − x Me x O11 − δ (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 °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.
KeywordsOxide ion conductor BiMeVOx Phase transitions Spectroscopy SEM XPS
This study was supported by the Aomori City Government. Deni S. Khaerudini gratefully acknowledges the scholarship from the Monbukagakusho (MEXT) of Japan.