Defect structure of the mixed ionic–electronic conducting Sr[Ti,Fe]Ox solid-solution system — Change in iron oxidation states and defect complexation

The oxidation/reduction behavior of iron in the Sr[Ti1 − yFey]Ox solid-solution system, for y ∈ [0.002; 0.05], under various oxygen partial pressures was examined through the use of electron paramagnetic resonance (EPR) spectroscopy. The results indicate that iron has been induced to move between di- tri- and tetravalent oxidation states. This results with the centers functioning as either a source (oxidation) or as a sink (reduction) for electrons. In particular it is shown that the reducibility of iron decreases with increasing iron content.