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New One-Dimensional Commensurate and Incommensurate Structural Forms of Sr-Co Oxide

Published online by Cambridge University Press:  15 February 2011

R. Christoffersen ,
A. J. Jacobson ,
S. L. Hegwood  and
L. Liu
R. Christoffersen
Affiliation:
Department of Chemistry, University of Houston, Houston, TX, 77204–5641
A. J. Jacobson
Affiliation:
Department of Chemistry, University of Houston, Houston, TX, 77204–5641
S. L. Hegwood
Affiliation:
Department of Chemistry, University of Houston, Houston, TX, 77204–5641
L. Liu
Affiliation:
Department of Chemistry, University of Houston, Houston, TX, 77204–5641
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Abstract

New forms of Sr-Co oxide with one-dimensional structures related to mixed-layer hexagonal perovskites have been synthesized and characterized by TEM. Crystals of Sr5Co2O12 grown from molten KOH flux and oxidized under slow cooling have structures based on a 3/2 ratio of mixed [Sr3CoO6] and [Sr3O9] layers. This is the first known structure with layers of this type stacked in a non-integer ratio, yielding chains of face-sharing octahedral and trigonal prismatic Co-sites with a 3 + 1 sequence along the c-axis. In oxygen-deficient Sr5Co2O12−x, the {110} structural modulation of the stoichiometric 5:4 phase becomes rotated to an irrational orientation, possibly in association with vacancy ordering, forming an incommensurate superstructure. For the compound Sr6Co5O15, previously known to have a 1/1 ratio of [Sr3CoO6] and [Sr3O9] layers with a 4 + 1 octahedral/trigonal prismatic site sequence, introduction of excess oxygen atoms leads to formation of a commensurate rhombohedral superlattice in which c is doubled relative to the stoichiometric 6:5 phase.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 453: Symposium R – Solid State Chemistry of Inorganic Materials , 1996 , 153
Copyright
Copyright © Materials Research Society 1997

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References

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