The effect of Mn-doping on the stability of ScSZ electrolyte under dual atmosphere of solid oxide fuel cells (SOFCs) was investigated in this study. Scandia stabilized zirconia electrolytes with and without 5 mol % MnO2 (ScSZ and Mn-ScSZ) were annealed under dual atmosphere of air and 1.2%H2O-H-2 at T = 1273 K. The surfaces of the ScSZ electrolytes in the air side were not changed after annealing. On the other hand, the surface of the Mn-ScSZ electrolyte in the fuel side was damaged; fine particles were formed on the surface and increased with time. After annealing for 4 weeks, dusting of the electrolyte surface was observed. Mn-doping to ScSZ and annealing under dual atmosphere simulating SOFCs induced the degradation of ScSZ electrolyte. (C) 2013 Elsevier B.V. All rights reserved.