Defect chemistry and charge transfer in praseodymium-barium cobaltites

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The conductivity of Pr1-xBaxCoO3-δ (x = 0 – 1/3) was measured in air as a function of temperature using a four-probe DC technique. The obtained data indicate that conductivity is governed by the following factors: hole concentration, hole mobility, oxygen exchange with the atmosphere, sample’s magnetic and phase state. The total conductivity was shown to be dominated by the small polaron holes over the whole temperature range studied. A combined defect chemical model based on the small polaron hopping mechanism was developed to quantitatively describe the conductivity temperature dependence. A novel approach was suggested for estimating the parameters of the model, yielding, among other quantities, the electron and hole mobilities, mobility activation energies, and transference numbers. This approach is not limited to the studied compounds and can be applied to the wide range of similar systems. The results obtained also demonstrate that praseodymium-barium cobaltites are promising cathode materials for solid oxide fuel cells due to their high conductivity and low activation energy of conduction.