An A- and B-Site Substitutional Study of SrFeO Perovskites for Solar Thermochemical Air Separation.

An A‑ and B‑site substitutional study of SrFeO perovskites (A'AB'BO, where A = Sr and B = Fe) was performed for a two‑step solar thermochemical air separation cycle. The cycle steps encompass (1) the thermal reduction of A'SrB'FeO driven by concentrated solar irradiation and (2) the oxidation of A'SrB'FeO in air to remove O, leaving N. The oxidized A'SrB'FeO is recycled back to the first step to complete the cycle, resulting in the separation of N from air and concentrated solar irradiation. A-site substitution fractions between 0 ≤ ≤ 0.2 were examined for A' = Ba, Ca, and La. B-site substitution fractions between 0 ≤ ≤ 0.2 were examined for B' = Cr, Cu, Co, and Mn. Samples were prepared with a modified Pechini method and characterized with X-ray diffractometry. The mass changes and deviations from stoichiometry were evaluated with thermogravimetry in three screenings with temperature- and O pressure-swings between 573 and 1473 K and 20% O/Ar and 100% Ar at 1 bar, respectively. A' = Ba or La and B' = Co resulted in the most improved redox capacities amongst temperature- and O pressure-swing experiments.