Redox Stability of Sm0.95Ce0.05Fe1-xCrxO3-δ Perovskite Materials

Abstract

This paper examines the relative REDOX stability and conductivity of new Cr-doped perovskite materials (Sm 0.95 Ce 0.05 Fe 1-x Cr x O 3-d , x ¼ 0-0.10) for potential use as anode materials and sensors for reducing gases at low temperatures. These perovskite materials were characterized by XRD, XPS and SEM. A reduction stability test revealed that these perovskites are stable at temperatures below 800 C under reducing conditions. The introduction of Cr in the lattice was found to be in the form of Cr þ3 and Cr þ6 . As a function of Cr content, the ratio of Cr þ3 /Cr þ6 was found to increase. The reduction treatment tended to decrease the concentration of lattice oxygen but the surface adsorbed oxygen was found to be higher in reduced samples as compared to fresh samples. This observation suggested that these materials have a tendency to recapture oxygen when exposed to air after the reduction treatment. The reduction treatment improved the electrical conductivity due to the formation of nanoparticles. The x ¼ 0.03 perovskite has highest electrical conductivity under both air and reducing atmospheres and shows the greatest promise for use in sensor applications for reducing gases at low temperatures.

Doped Samarium Ferrite Perovskites as Carbon and Sulfur Resistant Anodes for Low Temperature Solid Oxide Fuel Cells

“…By adding Ce as a doping agent at the A-site in SmFeO 3 we have been able to not only solve the reduction instability issue under reducing conditions, but also improve the electrical conductivity of the perovskite under reducing conditions by a transformation from p-type conductivity to n-type conductivity (12,13). Fine tuning the electrical and chemical properties is also possible by doping at the B-site (14)(15)(16)(17)(18)(19)(20). Furthermore, the enhanced stability and conductivity allowed three families of perovskites to show promise as SOFC anodes for pure hydrogen fuel (21)(22)(23).…”