Chemical and electronic characterization of cobalt in a lanthanum perovskite. Effects of strontium substitution

Journal Article · Fri Jan 15 00:00:00 EST 2010 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.10.008· OSTI ID:21372444

Hueso, Jose L; Holgado, Juan P; Pereniguez, Rosa; Mun, Simon; Salmeron, Miquel ^[1]; Caballero, Alfonso ^[1]

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1. Instituto de Ciencia de Materiales de Sevilla (CSIC-University of Seville) and Departamento de Quimica Inorganica, Universidad de Sevilla, Avda. Americo Vespucio 49, 41092 Seville (Spain)

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). Even though half of the La(III) is substituted by Sr(II), 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 state of the perovskite. The charge balance with Sr(II) species is reached by the formation of oxygen vacancies throughout the network, which explains the well-known increase in the reactivity of this substituted perovskite. O K-edge XAS experiments show that the Sr(II) species induce the transitions of d electrons of cobalt cations from low to high spin configuration. We propose that this change in spin multiplicity is induced by two cooperative effects: the oxygen vacancies, creating five coordinated cobalt atoms, and the bigger size of Sr(II) cations, aligning the Co-O-Co atoms, and favoring the overlapping of pi-symmetry cobalt and oxygen orbitals, reducing the splitting energy of e{sub g} and t{sub 2g} levels. - Graphical abstract: Change in spin multiplicity induced by the bigger size of Sr(II) cations, aligning the Co-O-Co atoms, and favoring the overlapping of pi-symmetry cobalt and oxygen orbitals.

• OSTI ID: 21372444
• Journal Information: Journal of Solid State Chemistry, Vol. 183, Issue 1; Other Information: DOI: 10.1016/j.jssc.2009.10.008; PII: S0022-4596(09)00490-3; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
CATIONS
COBALT COMPOUNDS
FINE STRUCTURE
LANTHANUM COMPOUNDS
OXIDES
PEROVSKITE
SPIN
STRONTIUM COMPOUNDS
STRONTIUM IONS
VACANCIES
X-RAY SPECTROSCOPY
ALKALINE EARTH METAL COMPOUNDS
ANGULAR MOMENTUM
CHALCOGENIDES
CHARGED PARTICLES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
IONS
MINERALS
OXIDE MINERALS
OXYGEN COMPOUNDS
PARTICLE PROPERTIES
PEROVSKITES
POINT DEFECTS
RARE EARTH COMPOUNDS
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS