The redox behaviors of Ni-gadolinia doped ceria (GDC) anodes with different compositions and microstructures were investigated. When the NiO-GDC composite particles prepared by spray pyrolysis were used for an anode (SP-cells), the decrease of the cell voltage during the redox cycles was smaller than that of the cell with anode using the mixed powder of NiO and GDC (Mix-cells). Current interruption and AC impedance measurements were examined before redox cycle, after 1st redox cycle, and after 10th redox cycles. The ohmic and polarization losses after 10th cycles for SP-cells were smaller than those for Mix cells. The morphology changes of the Ni-GDC anodes between before-redox cycle and after-10th redox cycles were observed by scanning electron microscopy (SEM). These results indicate that the use of NiO-GDC composite particles suppressed the excessive agglomerations of nickel grains during the redox cycles. (C) 2013 Elsevier B.V. All rights reserved.