High-Entropy Perovskites Pr(1−x)Sr(x)(Cr,Mn,Fe,Co,Ni)O(3−δ) (x = 0–0.5): Synthesis and Oxygen Permeation Properties

High-entropy perovskite oxides have already been studied in various fields owing to their high-entropy-induced properties. Partial substitution of an element by a lower valence element usually improves the oxygen permeability of perovskite oxides, but high substitution amounts may lead to structural instability. In this work, pure high-entropy perovskites Pr([Formula: see text])Sr(x)(Cr,Mn,Fe,Co,Ni)O([Formula: see text]) with high amounts Sr up to [Formula: see text] were synthesized via a sol–gel method. Several characterization methods prove that the solubility of Sr increases with higher temperatures of the heating treatment. The ceramic with [Formula: see text] shows a transition from semi-conductive to metallic behavior when the temperature reaches 873 K. Its oxygen flux is comparable to the low-entropy counterpart La(0.6)Sr(0.4)Co(0.5)Fe(0.5)O([Formula: see text]). A stable run of ca. 46.2 h was documented for oxygen permeation under an air/CO(2) gradient.