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Coulometric Titration Studies of Nonstoichiometric Nanocrystalline Ceria

  • O. Porat (a1), H. L. Tuller (a1), E. B. Lavik (a1) and Y.-M. Chiang (a1)

Abstract

Oxygen nonstoichiometry measurements in nanocrystalline ceria, x in CeO2-x, were performed using coulometric titration. The measurements reveal large apparent deviations from stoichiometry, of the order of 10−3 − 10−4 at T = 405 − 455 °C and Po2 = 0.21 − 10−5 atm, as compared to levels of ∼10−9 for coarsened materials under the same conditions. The level of nonstoichiometry is, however, larger then expected from previous electrical conductivity data of nanocrystalline ceria. In addition, x ∝ Po2 −½ while Σ ∝po2 −1/6. The observed dependence of x(Po2, T) can be explained by either the formation of neutral oxygen vacancies at or near the interface, or by surface adsorption.

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[4] Chiang, Y.-M., Lavik, E.B., Kosacki, I., Tuller, H.L. and Ying, J.Y., Appl. Phys. Lett. 69, 185 (1996).
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[7] Porat, O. and Tuller, H.L., J. Am. Ceram. Soc., in press.
[8] Porat, O. and Riess, I., J. Electrochem. Soc. 141, 1533 (1994).

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