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Unusual decrease in conductivity upon hydration in acceptor doped, microcrystalline ceria

Chueh, William C. and Yang, Chih-Kai and Garland, Carol M. and Lai, Wei and Haile, Sossina M. (2011) Unusual decrease in conductivity upon hydration in acceptor doped, microcrystalline ceria. Physical Chemistry Chemical Physics, 13 (14). pp. 6442-6451. ISSN 1463-9076.

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The impact of hydration on the transport properties of microcrystalline Sm_(0.15)Ce_(0.85)O_(1.925) has been examined. Dense, polycrystalline samples were obtained by conventional ceramic processing and the grain boundary regions were found, by high resolution transmission electron microscopy, to be free of impurity phases. Impedance spectroscopy measurements were performed over the temperature range 250 to 650 °C under dry, H_2O-saturated, and D_2O-saturated synthetic air; and over the temperature range 575 to 650 °C under H_2–H_2O atmospheres. Under oxidizing conditions humidification by either H_2O or D_2O caused a substantial increase in the grain boundary resistivity, while leaving the bulk (or grain interior) properties unchanged. This unusual behavior, which was found to be both reversible and reproducible, is interpreted in terms of the space-charge model, which adequately explains all the features of the measured data. It is found that the space-charge potential increases by 5–7 mV under humidification, in turn, exacerbating oxygen vacancy depletion in the space-charge regions and leading to the observed reduction in grain boundary conductivity. It is proposed that the heightened space-charge potential reflects a change in the relative energetics of vacancy creation in the bulk and at the grain boundary interfaces as a result of water uptake into the grain boundary core. Negligible bulk water uptake is detected under both oxidizing and reducing conditions.

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Haile, Sossina M.0000-0002-5293-6252
Additional Information:© 2011 The Owner Societies. Received 19th October 2010, Accepted 27th January 2011. We gratefully acknowledge the financial support of the National Science Foundation, Grant No. DMR-0604004. Additional support was provided by the National Science Foundation through the Caltech Center for the Science and Engineering of Materials, a Materials Research Science and Engineering Center (DMR-052056).
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Issue or Number:14
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Official Citation:Unusual decrease in conductivity upon hydration in acceptor doped, microcrystalline ceria William C. Chueh, Chih-Kai Yang, Carol M. Garland, Wei Lai and Sossina M. Haile Phys. Chem. Chem. Phys., 2011, 13, 6442-6451 DOI: 10.1039/C0CP02198A
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23296
Deposited By: Ruth Sustaita
Deposited On:19 Apr 2011 17:25
Last Modified:03 Oct 2019 02:45

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