Chemical and electronic characterization of cobalt in Lanthanumperovskites. Effects of Strontium substitution

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Two different cobaltites, LaCoO{sub 3} and La{sub 0.5}Sr{sub 0.5}CoO{sub 3-{delta}}, have been prepared and characterized by means of high energy Co K-edge and low energy O K-edge X-ray absorption spectroscopy (XAS). The partial substitution of La(III) by Sr(II) species induces important changes in the reactivity and electronic state of the perovskite, while little or no changes can be detected in the formal oxidation state of cobalt atoms. The presence of strontium cations induces two main effects in the chemical and electronic behavior of the perovskite. The charge balance with Sr(II) species is reached by the formation of oxygen vacancies throughout ... continued below

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Hueso, Jose L.; Holgado, Juan P.; Pereniguez, Rosa; Mun, Simon; Salmeron, Miquel & Caballero, Alfonso February 6, 2009.

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Two different cobaltites, LaCoO{sub 3} and La{sub 0.5}Sr{sub 0.5}CoO{sub 3-{delta}}, have been prepared and characterized by means of high energy Co K-edge and low energy O K-edge X-ray absorption spectroscopy (XAS). The partial substitution of La(III) by Sr(II) species induces important changes in the reactivity and electronic state of the perovskite, while little or no changes can be detected in the formal oxidation state of cobalt atoms. The presence of strontium cations induces two main effects in the chemical and electronic behavior of the perovskite. The charge balance with Sr(II) species is reached by the formation of oxygen vacancies throughout the network, which increases the reactivity of the perovskite, now more reducible than the original LaCoO{sub 3} perovskite. O K-edge XAS experiments indicate that the Sr(II) species cause d electrons of cobalt cations to change from low to high spin configuration. Our data allow us to propose that this change in spin multiplicity is induced by the bigger size of Sr(II) cations, which aligns the Co-O-Co atoms, and favors the overlapping of {pi}-symmetry cobalt and oxygen orbitals, reducing the splitting energy of e{sub g} and t{sub 2g} levels.

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  • Journal Name: Journal of the American Chemical Society

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  • Report No.: LBNL-1481E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 953688
  • Archival Resource Key: ark:/67531/metadc925912

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  • February 6, 2009

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  • Nov. 13, 2016, 7:26 p.m.

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  • Jan. 4, 2017, 4:46 p.m.

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Hueso, Jose L.; Holgado, Juan P.; Pereniguez, Rosa; Mun, Simon; Salmeron, Miquel & Caballero, Alfonso. Chemical and electronic characterization of cobalt in Lanthanumperovskites. Effects of Strontium substitution, article, February 6, 2009; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc925912/: accessed October 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.