Defects and transport in PrxCe1-xO2-δ: Composition trends

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 (PrxCe1-xO2-delta) solid solutions exhibit MIEC behavior in a relatively high and readily accessible oxygen partial pressure (P-O2) 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 Pr0.1Ce0.9O2-delta to include values of x = 0, 0.002, 0.008, 0.1, and 0.20 (in PrxCe1-xO2-delta) 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 PrxCe1-xO2-delta are discussed.