57Fe Mössbauer study into oxygen vacancy disorder in (Ba0.5Sr0.5)(Co0.8Fe0.2)O3−d

A 57Fe Mössbauer study of mixed ionic electronic conducting (Ba0.5Sr0.5)(Co0.8 57Fe0.08Fe0.12)O3−d (BSCF) has been made on samples of different oxygen content. The room-temperature spectra are found to depend strongly on oxygen stoichiometry. They reveal two magnetically and chemically different environments of the iron probes whose charge states and oxygen coordination are discussed. Analysis of spectral intensities provides confirmation of the close similarity of formation energies of different types of oxygen vacancies in BSCF. It is also shown that the distribution of oxygen vacancies on their sites of different coordination is far from random.