Chemical expansion in SOFC materials: Ramifications, origins, and mitigation

Non-stoichiometric oxides are frequently used in SOFC electrodes due to the ease with which they exchange oxygen with the atmosphere over their entire surface, as compared to composites limited to three phase boundaries (i.e. LSM/YSZ). The large fluctuations in oxygen content these materials exhibit during operation lead, not only to significant changes in transport properties, but also to a defect induced expansion, known as chemical expansion, potentially contributing to mechanical failure. In this presentation, new insights into the origins of chemical expansion, with consequent development of methods for reducing its impact in non-stoichiometric oxides, facilitated by collaborations of the authors, will be discussed.