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Synthesis and characterization of perovskite-type Sr(x)Y1-xFeO(3-delta) (0.63 <= x < 1.0) and Sr0.75Y0.25Fe1-yMyO3-delta (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)
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2013 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 200, 30-38 p.Article in journal (Refereed) Published
Abstract [en]

Oxygen-deficient ferrates with the cubic perovskite structure SrxY1-xFeO3-delta were prepared in air (0.71 <= x <= 0.91) as well as in N-2 (x=0.75 and 0.79) at 1573 K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3-delta=2.79(2) for x=0.75 to 3-delta=2.83(2) for x=0.91. Refinement of the crystal structure of Sr0.25Y0.25FeO2.29 using TOP neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and highresolution electron microscopy (HREM) studies of Sr0.75Y0.25FeO2.79 reveal a modulation along (1 0 0)(p) with G +/- similar to 0.4(1 0 0)(p) indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5-390 K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr0.75Y0.25Fe02.79 shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm/K in air at 298-673 K. At 773-1173 K TEC increases up to 17.2 ppm/K due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673 K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr0.75Y0.25Fe1-yMyO3-delta (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr0.75Y0.25Fe02.79. Only M=Ni has increased electrical conductivity compared to un-doped Sr0.75Y0.25Fe02.79.

Place, publisher, year, edition, pages
2013. Vol. 200, 30-38 p.
Keyword [en]
Perovskites, Neutron diffraction, Electron diffraction, High-temperature conductivity, Thermal expansion, Magnetic susceptibility
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-122339DOI: 10.1016/j.jssc.2013.01.008ISI: 000317158000005ScopusID: 2-s2.0-84873433673OAI: diva2:622467
Swedish Research Council

QC 20130522

Available from: 2013-05-22 Created: 2013-05-20 Last updated: 2013-05-22Bibliographically approved

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Zhao, Zhe
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