Compositions in the Gd0.8Sr0.2Co1-yFeyO3-delta (0less than or equal toyless than or equal to1.0) system were synthesized and the atomic structures were refined by Rietveld analysis of X-ray powder diffraction data. Thermal expansion and electrical conductivity were determined using dilatometry and four-point DC, respectively. A stable dual-phase perovskite system was shown to exist for all compositions. The primary phase had an orthorhombic symmetry (Pnma, #62) and the secondary phase had a cubic symmetry (Pm-3m, #221). Sr preferentially partitioned into the secondary cubic phase. Both the thermal expansion coefficient and the electrical conductivity decreased with increasing iron content. The potential for producing stable dual-phase perovskites opens up possibilities in material design for solid oxide fuel cell (SOFC) cathodes. (C) 2004 Elsevier B.V. All rights reserved.