The ability of RP-type cobaltites to accommodate carbonate groups: A new layered oxide Sr4Co2(CO3)O5.86

The possibility to introduce carbonate groups inside a pure cobalt based Ruddlesden Popper type matrix is demonstrated. This paper reports the synthesis as a single phase of a new layered oxycarbonate Sr4Co2(CO3)O5.86 and its structural characterizations at room temperature combining TEM observations and powder neutron diffraction data. Close structural relationships are observed with the homologous Sr4Fe3−x(CO3)xO10−4x series and deal with the presence of two specific carbonate configurations, namely coat hanger and flag. Magnetization measurements reveal a complex antiferromagnetic behavior below 50 K with three others transitions, at 160, 210 and 250 K. Such behavior can be ascribed to the latent reactivity in air of this largely oxygen deficient phase.

Structural model of the Sr4Co2(CO3)O5.86 oxycarbonate.Figure optionsDownload as PowerPoint slideHighlights
► Partial substitution of CO groups for Co species is efficient to stabilize a new RP3 cobaltite.
► HREM image combined with IR data and powder ND data confirm the structural model.
► From ND data, Fourier difference analysis evidences two specific carbonate orientations.