Electrochemically driven cation segregation in the mixed conductor La0.6Sr0.4Co0.2Fe0.8O3 − δ

Strontium segregation as function of electrochemical environment is measured for La0.6Sr0.4Co0.2Fe0.8O3 − δ using X-ray absorption spectroscopy. Gaseous Cr is used as a tracer to distinguish the bulk Sr from the segregated SrO at the surface via formation of SrCrO4. From the SrCrO4 to Cr2O3 ratio, the impact of cathodic and anodic overpotentials on Sr segregation is determined. While low anodic overpotentials were found to inhibit Sr segregation, higher overpotentials promote increased Sr segregation at the anode compared to the cathode. Oxygen vacancy concentration variations, caused by the overpotentials existing during operation, are identified as the driving mechanism for the Sr out-diffusion. Using this proposed Sr segregation mechanism, possible mitigation strategies are suggested.

► Sr segregation in MIEC material La0.6Sr0.4Co0.2Fe0.8O3 − δ due to electric potential..
► X-ray absorption spectrum of Cr tracer used as identifier.
► Ratio of Cr oxidation states yields dependency on applied potential.
► Results show involvement of oxygen vacancies.
► Possible mitigation strategies suggested.