The performance degradation of Ni-yttria-stabilized zirconia (Ni-YSZ) cermet anode was measured by impedance spectroscopy at 1000-1200 degrees C and humidity atmospheres under the open circuit condition in SOFCs. More significant crack formation can be observed at 1200 degrees C under 40% H2O-60% H-2 atmosphere. This crack formation gave rise to interruption of the ionic and electronic conduction path in the in-plane direction of anode layer, resulting in performance deterioration of anode. Focused ion beam-scanning electron microscopy (FIB-SEM) analyses were conducted for the anode layers, and then the 3D microstructures of Ni-YSZ anode were reconstructed. According to analysis of these data, the particle size of Ni was grown to the larger under higher temperature and humidity condition, accompanying with increase of isolated Ni-phase and the reduction of triple phase boundary (TPB) length. (C) 2014 Elsevier B.V. All rights reserved.