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DOI: 10.1039/A801798K (Paper) Reference Section for: J. Mater. Chem., 1998, 8, 2089-2093

Crystal structure, thermal and magnetic properties of La4Co3O9 . Phase relations for La4Co3O10–δ (0.00≤δ≤1.00) at 673 K

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Ole Henrik Hansteen, Helmer Fjellvåg* and Bjørn C. Hauback

Abstract

Phase relations and reoxidation behaviour is reported for samples with nominal composition La4Co3O10–δ(0.00≤delta;≤1.00) synthesized by isothermal reduction at 673 K. The crystal structure of La4Co3O9 has been determined on the basis of high-resolution powder X-ray diffraction and neutron diffraction data. The space group is Pnma, a=545.72 pm, b=2855.3 pm, c=565.42 pm at RT; Rwp(PXD)=6.2%,Rwp(PND)=9.0%, Rp(PXD)=4.4%,Rp(PND)=7.0%. Reduction of La4Co3O10 into La4Co3O9 leads to ordering of oxygen vacancies. Chains of corner-sharing CoO4 tetrahedra running along [100] are formed within the central-layer of each triple perovskite type layer of the Ruddlesden–Popper type structure of La4Co3O10 , whereas the top and bottom layers retain the perovskite type arrangement of corner-sharing CoO6 octahedra. La4Co3O9 orders antiferromagnetically at temperatures below TN=303±5 K. The magnetic structure is described on the basis of powder neutron diffraction data. The magnetic moments µtet=2.6±0.1µB and µoct=3.0±0.1µB correspond fairly well to spin only values for high-spin CoII .

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