The durability of the La0.8Sr0.2Ga0.8Mg0.2O3-delta (LSGM) electrolyte decreases when the Sm0.5Sr0.5Co3-delta(SSC) is used as the cathode. In this study, we developed five types of cathode [Pt, Au, SSC (annealed at 800 and 1200 degrees C, denoted SSC-800, SSC-1200, respectively), pelleted SSC, and SSC with a Sm0.2Ce0.8O1.9 (SDC). interlayer] to understand why the durability of LSGM in the presence of an SSC cathode declines. We found that, after constant polarization tests, the microstructure and cathodic polarization resistances of the Pt, SSC-800, SSC-1200 and SSC-pellet cathodes had changed, and the similar substances had separated from the crystalline grains at the grain boundaries, because of elemental interdiffusion at the interface. Hence, an SDC interlayer method was used to prevent the interdiffusion between the SSC cathode and the LSGM electrolyte. Consequently, the SDC interlayer is an effective method to prevent interdiffusion. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.