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Water Uptake and Conduction in Strontium Ytterbium Cerate

Published online by Cambridge University Press:  16 February 2011

G. W. Coffey
Affiliation:
Washington State University at Tri-Cities, Richland, Washington 99352, USA
L. R. Pederson
Affiliation:
Pacific Northwest Laboratory, P.O. Box 999, Richland, Washington 99352, USA
W. J. Weber
Affiliation:
Pacific Northwest Laboratory, P.O. Box 999, Richland, Washington 99352, USA
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Abstract

Water uptake and conduction have been studied in SrYb0.05Ce0.95O3-δ, a composition known to conduct protons, oxygen ions, and electrons, depending on temperature and environment. Water uptake kinetics evaluated by thermogravimetry occurred in two distinct stages: a rapid, initial weight gain (0.39±0.09 eV, attributed to grain boundary and near surface hydration) followed by a much slower uptake (2.8±0.4 eV, attributed to hydration of the bulk grains). From cyclic voltammetry and mass spectrometry measurements for a cell exposed to asymmetric conditions, currents and activation energies for electronic, oxygen ion, and proton conduction were determined. The activation energy for electronic conduction, 0.90±0.09 eV, is believed to be artificially high due to the increase in electron carrier concentration with increased temperature. The activation energy for oxygen ion conduction (0.97±0.10 eV) agrees well with other oxygen conductors. Proton conduction appeared to follow two different mechanisms: a low temperature process characterized by an activation energy of 0.42±0.04 eV, and a high temperature process, characterized by an activation energy of 1.38±0.13 eV. A possible explanation is that proton conduction at low temperatures is dominated by grain boundaries and is dominated by bulk conduction at higher temperatures.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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