Ionic and electronic conductivity in a Bi2O3-based material

Non-negligible electrode polarization in cells for transference number determination of bismuth oxide based materials, using classical EMF measurements, leads to apparent oxygen ion transference numbers lower than their true values. DC voltage–current measurements combined with impedance measurements were performed to eliminate the influence of electrode polarization resistance. Linear dependence of overpotential on ionic current and constant electronic resistance during the experiment were assured by a small oxygen partial pressure gradient and appropriate choice of external voltage. The polarization processes were analyzed by impedance spectroscopy. At higher temperatures (750–850 °C) for bismuth oxide based materials like Bi3Nb0.8 W0.2O7.1 compound with platinum electrodes, the results of ion transference numbers are comparable to those obtained by conventional EMF measurement. The presented method with voltage source can support the modified EMF measurement with external load resistors, so called Gorelovʹs method, by operation at lower electrode overpotential being advantageous at low temperatures when electrode polarization effects are significant.