Reverse uptake of oxygen from La1−xSrx (Fe3+/Fe4+)O3±δ perovskite-type mixed oxides (x = 0.00, 0.15, 0.30, 0.40, 0.60, 0.70, 0.80, 0.90)

Abstract Substituted perovskite-type mixed oxides of the general formula La 1− x Sr x (Fe 3+ /Fe 4+ )O 3± δ were prepared for x =0.00, 0.15, 0.30, 0.40, 0.60, 0.70, 0.80, and 0.90 by the ceramic method and heating at 1000 °C. The prepared solids were examined by X-ray diffractogram (XRD) for their crystal structure and by Mossbauer spectroscopy at RT for the kind and the exact amount of iron containing crystal phases. The gradual substitution of La 3+ by Sr 2+ results in a quantitative development of the crystal phase SrFe 4+ O 3 and the corresponding diminution of the rest phases containing iron, i.e. LaFeO 3 and Fe 2 O 3 (traces). Detailed thermogravimetric O 2 /temperature-programmed desorption (TPD) experiments showed that the solids release oxygen when heated in a He atmosphere which is strictly proportional to the amount of Fe 4+ in the samples. Quantitative calculations showed that exactly one atom of oxygen is released per unit cell of Sr–Fe–O perovskite, which contains four Sr(Fe 4+ /Fe 3+ )O 3± δ units. The phenomenon is reversible and the solids re-adsorb fast and quantitatively the lost lattice oxygen when gaseous oxygen is admitted back to the system.