High conductivity and high density SrCe0.5Zr0.35Y0.1A0.05O3-δ (A = Gd, Sm) proton-conducting electrolytes for IT-SOFCs

Abstract

A novel Sr-based perovskite electrolyte, SrCe0.5Zr0.35Y0.1Gd0.05O3-δ, was successfully synthesized and characterized in comparison with SrCe0.5Zr0.35Y0.1Sm0.05O3-δ for possible use in proton-conducting solid oxide fuel cells. Indexing and subsequent Rietveld refinement confirm that both materials crystallize in the orthorhombic symmetry with Pbnm space group. Scanning electron microscopy images show the highly dense structure with the relative densities of 96% and 97% for Gd and Sm-doped sample, respectively. Electrochemical impedance measurements in wet 5% hydrogen at 700 °C shows that the conductivity of SrCe0.5Zr0.35Y0.1Gd0.05O3-δ and SrCe0.5Zr0.35Y0.1Sm0.05O3-δ were 5.701 ×10−3 S cm−1 and 5.257 × 10−3 S cm−1, respectively. The ionic conductivities of both samples increase in the wet hydrogen compared with that of dry hydrogen atmosphere. This indicates the enhancement of protonic conduction mechanism from introducing water in electrochemical impedance measurement. The proton conduction takes place at a lower temperature than conventional solid oxide fuel cell (SOFC) which makes SrCe0.5Zr0.35Y0.1(Gd/Sm)0.05O3-δ good electrolytes for intermediate-temperature solid oxide fuel cell (IT-SOFC).