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Defect chemistry of yttrium-doped barium zirconate: a thermodynamic analysis of water uptake

Yamazaki, Yoshihiro and Babilo, Peter and Haile, Sossina M. (2008) Defect chemistry of yttrium-doped barium zirconate: a thermodynamic analysis of water uptake. Chemistry of Materials, 20 (20). pp. 6352-6357. ISSN 0897-4756. doi:10.1021/cm800843s.

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Thermogravimetry has been used to evaluate the equilibrium constants of the water incorporation reaction in yttrium-doped BaZrO3 with 20-40% yttrium in the temperature range 50-1000 °C under a water partial pressure of 0.023 atm. The constants, calculated under the assumption of a negligible hole concentration, were found to be linear in the Arrhenius representation only at low temperatures (≤500 °C). Nonlinearity at high temperatures is attributed to the occurrence of electronic defects. The hydration enthalpies determined here range from -22 to -26 kJ mol^-1 and are substantially smaller in magnitude than those reported previously. The difference is a direct result of the different temperature ranges employed, where previous studies have utilized higher temperature thermogravimetric measurements, despite the inapplicability of the assumption of a negligible hole concentration. The hydration entropies measured in this work, around -40 J K^-1 mol^-1, are similarly smaller in magnitude than those previously reported and are considerably smaller than what would be expected from the complete loss of entropy of vapor-phase H2O upon dissolution. This result suggests that substantial entropy is introduced into the oxide as a consequence of the hydration. The hydration reaction constants are largely independent of yttrium concentration, in agreement with earlier reports.

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Haile, Sossina M.0000-0002-5293-6252
Additional Information:© 2008 American Chemical Society. Received March 23, 2008. Revised Manuscript Received July 22, 2008. This work was supported by U.S. Department of Energy, the Gordon and Betty Moore Foundation, and by JSPS Postdoctoral Fellowships for Research Abroad.
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Department of Energy (DOE)UNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Subject Keywords:temperature protonic conductors; perovskite-type oxides; transport-properties; vapor solubility; charge-carriers; single-crystal; conductivity; impedance; ceramics; BACEO3
Issue or Number:20
Record Number:CaltechAUTHORS:YAMcm08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13352
Deposited By: Tony Diaz
Deposited On:23 Apr 2009 16:35
Last Modified:08 Nov 2021 22:37

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