Structural aspects of Pr1-xSrxFeO3-w

Stange, Marit, Lindén, Johan, Kjekshus, Arne, Binsted, Norman, Weller, M. T., Hauback, Bjørn C. and Fjellvåg, Helmer (2003) Structural aspects of Pr1-xSrxFeO3-w. Journal of Solid State Chemistry, 173 (1), 148-163. (doi:10.1016/S0022-4596(02)00116-0).

Abstract

Structural aspects of the distorted perovskite ABO(3) phase Pr1-xSrxFeO3-w,x = 0.00-0.80, w = 0.000-0.332, were studied by powder X-ray diffraction, powder neutron diffraction, Fe-57 Mossbauer spectroscopy, and Fe K-, Sr K-, and Pr L-III-edge EXAFS techniques. The diffraction data revealed no indications for ordering of Pr and Sr at the A site, nor for oxygen vacancy ordering at O sites for heavily reduced samples. Mossbauer spectroscopy showed octahedral, square pyramidal, and tetrahedral Fe coordinations with relative amounts closely following the predictions for a binomial distribution of oxygen vacancies. In addition to Fe3+ and Fe4+, also Fe5+ appears at 77 K for (G-type) antiferromagnetic samples with high average Fe valence. This suggests dynamic 2 Fe4+ Fe3+ + Fe5+ fluctuations. At 296 K, a mixed valence Fe(3+n)+ component significantly improved the fit of Mossbauer spectra for the most oxidized paramagnetic samples. The qualitative EXAFS study shows that the local environments for Fe, Pr, and Sr strongly depend on x and w. The local Pr- and Sr-site geometries differ significantly from the cubic average structure for Pr0.50Sr0.50FeO2.746.

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