Comparative characterization of thermodynamic, electrical, and electrochemical properties of Sm0.5Sr0.5Co1−xNbxO3−δ (x = 0, 0.05, and 0.1) as cathode materials in intermediate temperature solid oxide fuel cells

► Sm0.5Sr0.5Co1−xNbxO3−δ (x = 0, 0.05, and 0.1) are investigated by the effect of Nb. ► Electrical properties are identified by a four-terminal d.c. arrangement in air. ► Electrochemical performances are investigated using an Ni-GDC anode-supported cell. ► Thermodynamic properties are estimated from the oxygen isotherms.