Strontium and iron co-doped lanthanum cobaltites (La1-xSrxCo1-yFeyO3-δ, LSCF) show good oxygen ion and electronic conductivity and fast oxygen surface exchange kinetics at temperatures between 600 and 800 °C, and is considered today one of the most promising class of cathode materials for intermediate-temperature solid oxide fuel cells. Despite its technological importance, the phase stability of the LSCF perovskite has not yet been fully mapped out and may be critical for the use of the materials during long-term operation. For cells with LSCF or LSCF/CGO (CGO: gadolinia doped ceria) cathodes, partial decomposition of the perovskite phase has been reported as a possible cause of high degradation rates. In addition, the LSCF perovskite is prone to react with gas species, such as CO2 and water vapor, which are present in atmospheric air, or species evaporated from stack components (interconnects and glass seals), such as chromium- or boron-containing gas species. In this paper, a thermodynamic database for the multicomponent La-Sr-Co-Fe-O system is presented which was established employing the CALPHAD (CALculation of PHAse Diagrams) methodology. The phase stability of LSCF itself is then discussed as a function of composition, temperature and oxygen partial pressure. The results show that the LSCF perovskite phase will decompose at high Sr or Co content, at elevated temperature, or at reduced oxygen partial pressure. The LSCF reactivity towards gas impurities is further analyzed under realistic SOFC operating conditions.
|Title of host publication||Proceedings of 11th European SOFC and SOE Forum 2014|
|Publisher||European Fuel Cell Forum|
|Publication status||Published - 2014|
|Event||European fuel cell 2014 - 11th European SOFC and SOE Forum 2014 - Lucerne, Switzerland|
Duration: 1 Jul 2014 → 4 Jul 2014
|Conference||European fuel cell 2014 - 11th European SOFC and SOE Forum 2014|
|Period||01/07/2014 → 04/07/2014|