STRUCTURAL CHEMISTRY OF SRMN1-XFEXO3-DELTA,X-APPROXIMATE-TO-0.3

A polycrystalline sample of nominal composition SrMn0.7Fe0.3O3-delta w as prepared by standard ceramic techniques and investigated at room te mperature by iodometry, Fe-57 Mossbauer spectroscopy and neutron powde r diffraction. The former two techniques established;delta = 0.11 +/- 0.01. Neutron diffraction showed that the sample was biphasic. The maj or component [98.3 (5)% by mass] was a 10H perovskite [space group P6( 3)/mmc; a = 5.45035(5), c = 22.3735(2) Angstrom], with the Sr-O layers adopting a cccchcccch stacking sequence. A full structural refinement showed the composition to be SrMn0.72Fe0.28O2.87. The minor phase was a pseudo-cubic perovskite. The Mossbauer data suggest that the oxygen vacancies in the major phase are predominantly found in the coordinat ion shell of Fe3+ cations. The sample did not show long-range magnetic order at room temperature.