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In-SituEELS Analysis of Cobalt Valence in La1-xSrxCoO3-y

Published online by Cambridge University Press:  02 July 2020

J.S. Yin
Affiliation:
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332
Z.L. Wang
Affiliation:
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332
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Extract

Transition and rare earth metal elements have played a vital role in synthesis of functional and smart materials because of their unique electronic structures and mixed valences. Experimental measurement of the valence states is thus important for understanding the mechanism which drives the functional properties. Lai1.xSrxCoO3-y(LSCO), for example, is an ionic conductor with potential applications in fuel cells and many other fields. In this type of materials, the anion deficiency is directly associated with the ratio of Co2+/Co3+ (or Co3+/Co4+) present in the specimen. It is known that the anion deficiency of the material depends on the operation temperature, but a direct measurement of anion deficiency is a challenge to existing microscopy techniques. In this paper, we present the in-situ analysis of Co valence in LSCO using electron energy-loss spectroscopy (EELS) in a transmission electron microscope.

LSCO thin films (with x = 0.5) were grown on polished MgO(00l) substrate by liquid source metal-organic chemical vapor deposition (MOCVD) method [1].

Type
In Situ Studies in Microscopy
Copyright
Copyright © Microscopy Society of America 1997

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