Structural chemistry of SrMn1 –xFexO3 –δ, x≈ 0.3

Abstract

A polycrystalline sample of nominal composition SrMn_0.7Fe _0.3O_{3 –δ} was prepared by standard ceramic techniques and investigated at room temperature by iodometry, ⁵⁷ Fe Mössbauer spectroscopy and neutron powder diffraction. The former two techniques established δ= 0.11 ± 0.01. Neutron diffraction showed that the sample was biphasic. The major component [98.3(5)% by mass] was a 10H perovskite [space group P6₃/mmc; a= 5.45035(5), c= 22.3735(2)Å], with the Sr–O layers adopting a cccchcccch stacking sequence. A full structural refinement showed the composition to be SrMn_0.72Fe_0.28O_2.87. The minor phase was a pseudo-cubic perovskite. The Mössbauer data suggest that the oxygen vacancies in the major phase are predominantly found in the coordination shell of Fe³⁺ cations. The sample did not show long-range magnetic order at room temperature.