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

Phase relations and reoxidation behaviour is reported for samples with nominal composition La4Co3O10-delta (0.00 less than or equal to delta less than or equal to 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; R-wp(PXD) = 6.2%, R-wp(PND) = 9.0%, R-p(PXD) = 4.4%, R-p(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 T-N = 303 +/- 5 K. The magnetic structure is described on the basis of powder neutron diffraction data. The magnetic moments mu(tet) = 2.6 +/- 0.1 mu(B) and mu(oct) = 3.0 +/- 0.1 mu(B) correspond fairly well to spin only values for high-spin Co-II.