In the last years, several mixed ionic-electronic conducting (MIEC) materials, such as Sr(Co,Fe)O₃-based perovskites, have attracted increasing interest owing to their excellent ionic and electronic transport properties. In particular, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) shows a high oxygen permeation flux, thus making it a promising candidate for intermediate temperature solid oxide fuel cell cathodes and dense ceramic oxygen permeation membranes. However, several issues, such as its long-term behaviour (stability) as a function of oxygen partial pressure, temperature or in the presence of other gas components (e.g., CO₂), are still subject of investigation.

In the present study, polycrystalline BSCF as well as related perovskite compositions of interest for similar applications (e.g., La_0.58Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF), Pr_0.58Sr_0.4Co_0.2Fe_0.8O_3-δ (PSCF)) were investigated as bulk samples in an oxygen pump setup with respect to the conductivity behaviour as a function of oxygen partial pressure and temperature. Moreover, surface exchange (k^δ) and bulk diffusion (D^δ) coefficients have been determined from measurements on thick film and thin film samples by means of further electro­chemical techniques (impedance spectroscopy, conductivity relaxation in the frequency domain) and are compared with values taken from a literature survey.

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1. Determination of oxygen chemical transport parameters of MIEC materials from electrochemical impedance spectroscopy
2. Oxygen permeation through asymmetric perovskitic membranes