Study of phase stabilization and oxide–ion conductivity in BICUMGVOX solid electrolyte

Samples of Cu(0.10 − x)–Mgx doubly substituted bismuth vanadate, BICUMGVOX (Bi2Cu0.10 − xMgxV0.9O5.35) were synthesized by the citrate sol–gel method. The influence of Cu-Mg substitution on phase stability and oxide-ion performance have been investigated using X-ray powder diffraction (XRPD), FT–IR spectroscopy, differential thermal analysis (DTA) and AC impedance spectroscopy. The highly conductive γʹ–phase was effectively stabilized at room temperature for compositions with x ≥ 0.06 whose thermal stability increases with Mg content. The complex plane plots of impedance for polycrystalline samples showed the variation of equivalent circuit models with composition at isothermal conditions. It was found that the highest value of conductivity 1.5 × 10− 3 S.cm− 1 at 300 °C is obtained from the composition x = 0.06 whose conductivity at 600 °C also reaches its maximum value of 4.9 × 10− 2 S.cm− 1.