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Evaluation of Variously Doped BaCeO3 Ceramics as Protonic Conductors

Published online by Cambridge University Press:  28 February 2011

J.F. Liu
Affiliation:
Henry Krumb School of Mines, Columbia University, New York, NY 10027
A.S. Nowick
Affiliation:
Henry Krumb School of Mines, Columbia University, New York, NY 10027
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Abstract

Nd—doped BaCeO3 is reported to be an excellent high—temperatureprotonic conductor, while the Gd—doped material is not. In order to better understand the role of different dopants, we have studied BaCeO3 doped with 5 mol% of each Nd3+, Eu3+, Gd3+, Yb3+ and Ca2+. In each case samples were treated in an appropriate gas atmosphere at 900ºC followed by measurement from 25 to 200ºC in a “frozen—in”state. Protonic conduction was deduced from the isotope effect, i.e. comparing conductivity after treatment in D2O—saturated gas with that for H20,as well as by the change between wet and dry treatments. In addition, we measured H2O uptake by observing the weight change between wet and dry treatments, and also carried out some galvanic cell measurements. It was concluded that, of the above dopants, only Nd and Ca give rise to appreciable protonic conduction. In the Nd case, the low activation energy of 0.54 eV is probably the proton hopping energy. On the other hand, Eu, Gd and Yb—doped materials appear to show the dominance of oxygenion conduction in the low temperature range and mixed oxygen—ion and electron—hole conductivity at elevated temperatures. The most likely reason for these differences seems to be centered on the ionic radii of the dopants.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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