Praseodymium-cerium oxide (PCO) solid solutions exhibit mixed ionic electronic conductivity (MIEC) behavior in a relatively high and readily accessible oxygen partial pressure (P(O(2))) regime and as such serve as a model system for investigating the correlation between thermodynamic and kinetic properties and performance figures of merit in the areas of high temperature energy conversion, automotive control, and gas sensing applications. In this paper, we present measurements on the non-stoichiometry of Pr(0.1)Ce(0.9)O(2-δ) and develop a defect equilibria model to predict the dependence of the concentration of all the dominant charge carriers on temperature, P(O(2)), and Pr fraction. The predictive model is then employed to describe the measured electrical conductivity and oxygen nonstoichiometry whereby pre-exponentials and enthalpies of defect formation and migration are extracted.

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Nonstoichiometric mixed ionic and electronic conductors (MIECs) find use as oxygen permeation membranes, cathodes in solid oxide fuel cells, oxygen storage materials in three-way catalysts, and chemoresistive gas sensors. Praseodymium-cerium oxide (Pr x Ce 1Àx O 2Àd ) solid solutions exhibit MIEC behavior in a relatively high and readily accessible oxygen partial pressure (P O 2 ) regime and as such serve as model systems for investigating the correlation between thermodynamic and kinetic properties as well as exhibiting high performance figures of merit in the above applications. In this paper, we extend recently published results for Pr 0.1 Ce 0.9 O 2Àd to include values of x 5 0, 0.002, 0.008, 0.1, and 0.20 (in Pr x Ce 1Àx O 2Àd ) to test how both defect and transport parameters depend on Pr fraction. Important observed trends with increasing x include increases in oxygen ion migration energy and MIEC and reductions in vacancy formation and Pr ionization energies. The implications these changes have for potential applications of Pr x Ce 1Àx O 2Àd are discussed.

Praseodymium cerium oxide (Pr x Ce 1−x O 2−δ ) is a mixed ionic-electronic conductor with high levels of nonstoichiometry under oxidizing conditions resulting from reduction of Pr 4+ to Pr 3+ . Coulometric titration measurements performed on (Pr x Ce 1−x O 2−δ ) with x = 0.2 are generally consistent with those derived from electrical conductivity measurements. Nevertheless, a somewhat larger degree of nonstoichiometry measured via coulometric titration implies that non-charged defect species may be significant in the system.