In this study, the miscrostructural change of the LSCF/SDC/YSZ system upon discharge was analyzed quantitatively by the focused ion beam-scanning electron microscopy as well as the transmission electron microscopy. It is widely recognized that the formation of highly-resistive SrZrO3 phase degrades the cell performance in this system. In fact, the ohmic loss and cathodic overpotential increased in response to the six-fold increase in the volume of SrZrO3 phase after 400 h of discharge at 1000 degrees C. However, the microstructural change proceeded in the whole part of this system, indicating that various degradation factors need to be considered; e.g., 1) the agglomeration of SDC and LSCF phases, 2) the reduction in triple phase boundary length, and 3) the formation of ceria-zirconia solid solution. (C) 2016 Elsevier B.V. All rights reserved.