AC impedance and cyclic voltammetric investigations on BIPBVOX solid electrolyte

Samples of BIPBVOX.x (Bi₂V_1−xPb_xO_5·5−x/2), in the composition (x) range 0·05 ≤ x ≤ 0·20, were prepared by the ethylene glycol–citric acid sol–gel synthesis route. Structural investigations were carried out by X-ray diffraction, Fourier transform infrared spectroscopy and differential thermal analysis. The highly conducting γ′-phase was effectively stabilized at room temperature (35°C) for compositions with x ≥ 0·17. Alternating current impedance spectra revealed that the conductivity is mainly due to the grain contribution to oxide ion conductivity. At 300°C, the highest value of conductivity (6·234 × 10⁻⁵ S/cm) was obtained for the composition x = 0·15, while the highest value of conductivity at 600°C (0·65 S/cm) was observed for x = 0·17. Cyclic voltammetric measurements showed reversible redox reactions of vanadium and irreversible redox reaction of the bismuth (III) ion (Bi³⁺) in the BIPBVOX system during the first cathodic and anodic sweep. However, a higher stability against the reduction of the bismuth (III) ion to metallic bismuth was seen for x = 0·20.