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 1- x Sr x (Cr,Mn,Fe,Co,Ni)O 3-δ with high amounts Sr up to x = 0.5 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 x  = 0.5 shows a transition from semi-conductive to metallic behavior when the temperature reaches 873K. Its oxygen flux is comparable to the low-entropy counterpart La 0.6 Sr 0.4 Co 0.5 Fe 0.5 O 3-δ . A stable run of ca. 46.2 h was documented for oxygen permeation under an air/CO 2 gradient.