Chen D, Cao Y, Weng D, et al. Defect and Transport Model of Ceria–Zirconia Solid Solutions: Ce0. 8Zr0. 2O2? δ An Electrical Conductivity Study[J]. Chemistry of Materials, 2014, 26(17): 5143-5150.
ABSTRACT
The electrical conductivity (σ)ofCe0.8Zr0.2O2?δwas measured andmodeled using a defect chemical-based model including contributions from singlyand doubly ionized oxygen vacancies, acceptor impurities, and small polaronelectrons. By analyzing thepO2dependence ofσin terms of the defect model, atransition between an impurity dominated regime at highpO2and lowertemperature to one controlled by the simultaneous generation of electrons anddoubly ionized oxygen vacancies at lowpO2and higher temperature is identified. Ateven lowerpO2, or equivalently larger deviations from stoichiometry, evidence ispresented for a further transition to singly ionized oxygen vacancies accompanyingelectron generation. Temperature induced conductivity relaxation measurementsare successfully applied in deconvoluting electron generation and migrationcontributions to the activation energy. Key parameters are extracted including theenthalpy of reductionHrof 2.87±0.06 eV and the electron hopping or migrationenergy of 0.354±0.005 eV. Both the activated electron mobility and the broad maximum in conductivity observed under themost reducing conditions support the small polaron model for electron transport in Ce0.8Zr0.2O2?δ. Consistent with earlierfindings, Zr, though isovalent with Ce, markedly enhances the reducibility, and thereby the oxygen storage capability of ceria?zirconia solid solutions
