Title

Magnetic and Mössbauer Spectral Study of Mixed Valent La₀.₂Sr₀.₈Cu₀.₂Fe₀.₈O₂.₆₈ and Related Perovskites

Abstract

The La0.2Sr0.8Cu1-xFexO 3-δ perovskites are important because they are mixed electron and oxygen anion conductors and thus are able to serve as dense oxygen separation membranes. In order to better understand the mechanism for this separation a Mössbauer spectral study has been carried out to determine the ratio of iron(III) to iron(IV) in these mixed valent compounds. The Mössbauer spectra of La0.2Sr0.8Cu0.2Fe0.8O 3-δ obtained between 4.2 and 78 K reveal that its Néel temperature is ∼75 K and the two well-resolved magnetic sextets observed between 4.2 and 45 K indicate the presence of trapped valence iron(III) and iron(IV). At 4.2 K the respective hyperfine fields are 454 and 299 kOe and the isomer shifts are 0.388 and 0.057 mm/s. The iron(III) to iron(IV) ratio is 1.20, a ratio which yields a δ value of 0.32 and, if one assumes the presence of only copper(II), à corresponding stoichiometry of La0.2Sr0.8Cu0.2Fe0.8O 2.68. © 1999 American Institute of Physics.

Department(s)

Chemistry

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1999 American Institute of Physics (AIP), All rights reserved.


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