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29Si MAS-NMR study of oxide conductors derived from the apatite-type La9.33Si6O26 compound

29Si MAS-NMR study of oxide conductors derived from the apatite-type La9.33Si6O26 compound The preparation of (La9.33−2x/3Sr x □0.67−x/3)Si6O24O2 (0 ≤ x ≤ 2) samples with different amounts of cation vacancies is reported. Structure and unit-cell parameters were deduced by Rietveld analysis of XRD patterns. Structural features that enhance oxygen conductivity in Sr-doped apatites are discussed. Up to three components were detected in 29Si MAS-NMR spectra which change with the amount and distribution of cation vacancies. In general, oxygen conductivity increases with the amount of vacancies at La1 (6h) sites, passing through a maximum for x = 0.4. In the case of activation energy, a minimum is detected near x = 1.2, indicating that entropic and enthalpic change in different ways. The presence of cation vacancies should enhance oxygen hopping along c-axis; however, the analysis of the frequency dependence of conductivity suggests that oxygen motions are produced along three axes. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ionics Springer Journals

29Si MAS-NMR study of oxide conductors derived from the apatite-type La9.33Si6O26 compound

Madani, A.; Sobrados, I.; Inoubli, A.; Chefi, S.; Kahlaoui, M.; Sanz, J.
Ionics , Volume 16 (8) – Jul 13, 2010
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References (24)

Publisher
Springer Journals
Copyright
Copyright © 2010 by Springer-Verlag
Subject
Chemistry; Condensed Matter Physics; Optical and Electronic Materials; Renewable and Green Energy; Electrochemistry
ISSN
0947-7047
eISSN
1862-0760
DOI
10.1007/s11581-010-0457-7
Publisher site
See Article on Publisher Site

Abstract

The preparation of (La9.33−2x/3Sr x □0.67−x/3)Si6O24O2 (0 ≤ x ≤ 2) samples with different amounts of cation vacancies is reported. Structure and unit-cell parameters were deduced by Rietveld analysis of XRD patterns. Structural features that enhance oxygen conductivity in Sr-doped apatites are discussed. Up to three components were detected in 29Si MAS-NMR spectra which change with the amount and distribution of cation vacancies. In general, oxygen conductivity increases with the amount of vacancies at La1 (6h) sites, passing through a maximum for x = 0.4. In the case of activation energy, a minimum is detected near x = 1.2, indicating that entropic and enthalpic change in different ways. The presence of cation vacancies should enhance oxygen hopping along c-axis; however, the analysis of the frequency dependence of conductivity suggests that oxygen motions are produced along three axes.

Journal

Ionics – Springer Journals

Published: Jul 13, 2010

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