A B S T R A C TIn the pursuit for solid oxide fuel cell (SOFC) cathode materials that can operate over a wide temperature range, especially at low temperatures such as 600 C, perovskite structure materials La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF), Ba 0.5 Sr 0.5 Co 0.2 Fe 0.8 O 3 (BSCF), and Sm 0.5 Sr 0.5 Co 0.2 Fe 0.8 O 3 (SSCF) are studied. Their electrochemical performance is compared by electrochemical impedance spectroscopy (EIS) at 600 C, 700 C and 800 C for 100 hrs through an AISI 441 interconnect/cathode/yttria-stabilized zirconia (YSZ) electrolyte half-cell structure. The BSCF cathode has the smallest polarization resistance at 600 C, closely followed by the SSCF cathode; the LSCF cathode has the smallest polarization resistance working at 700 C; the SSCF cathode has the smallest polarization resistance working at 800 C, closely followed by the LSCF cathode. From 600-800 C, SrCrO 4 phase forms on the SSCF cathodes near the interconnect while BaCrO 4 phase forms on the BSCF cathodes near the interconnect. For the LSCF cathodes, however, SrCrO 4 phase is only detected at 700 C and 800 C. Cr species diffusion to and poisoning of the cathodes do not directly correlate with the half-cell performance. Lattice constant, stoichiometry, particle size, Cr deposition, and working temperature are important factors to consider.