(Invited) Defect Chemistry of Mixed Conducting Oxides for SOFC Cathode

Abstract

Two universal defect chemistry models are presented to relate the properties of a variety of p type perovskite conductors, including chromites, manganites, and ferrites, which can be tailored as mixed ionic and electronic conductors (MIECs). It is found that oxygen nonstoichiometry in these p type MIECs can be correlated using a term we call the ability for oxygen vacancy generation (AOG). The values of AOG can be obtained by simulating the electronic conductivity as a function of oxygen activity and temperature with two existing universal models that are based on the concept of delocalized electron holes and localized electron holes, respectively. Both the global defect chemistry models yield a significant difference of ability for oxygen vacancy generation for all the oxides in this study, which allows us to better understand and predict the electrochemical properties of perovskite type p-type conductors.