Abstract

Effects of iron doping on the functional properties of (La,Sr)CrO3-based electrode materials have been appraised in a range of conditions relevant for SOFCs and other electrochemical applications. Mössbauer spectroscopy of perovskite-type (La0.75Sr0.25)0.95Cr1−xFexO3−δ (x=0.3–0.4), combined with thermogravimetry and X-ray diffraction, shows that the prevailing oxidation state of iron cations in both oxidizing and reducing atmospheres remains 3+. The redox behavior and transport properties are, therefore, essentially governed by Cr3+/4+ couple, leading to dominant p-type electronic conduction in the oxygen partial pressure range from 0.5 down to 10−20atm at 973–1223K. The total conductivity and Seebeck coefficient variations indicate that the electronic transport decreases with iron additions as the hole concentration and mobility become lower. The partial ionic conductivity estimated from the steady-state oxygen permeability under air/H2–H2O–N2 gradients is 0.05–0.08Scm−1 at 1223K and p(O2)=10−17atm, and increases with x due to rising oxygen deficiency. A similar tendency was observed for chemical expansion studied by the controlled-atmosphere dilatometry, whereas the average thermal expansion coefficients are almost independent of x and vary from 11.1–11.3×10−6K−1 in air down to 10.3–10.5×10−6K−1 in CO–CO2 at 350–1370K. The electrochemical activity of porous (La0.75Sr0.25)0.95Cr0.7Fe0.3O3−δ anodes with Ce0.8Gd0.2O2−δ interlayers, applied onto LaGaO3-based solid electrolyte, is higher compared to (La0.75Sr0.25)0.95Cr0.5Mn0.5O3−δ when no metallic current-collecting layers are used. Increasing iron content lowers the electrode performance in wet H2-containing atmospheres, in correlation with electronic conduction.

Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.