Effects of Partial Substitution of CeO2 with M2O3 (M = Yb, Gd, Sm) on Electrical Degradation of Sc2O3 and CeO2 Co-doped ZrO2

Scandia-stabilized zirconia co-doped with CeO2 is a promising electrolyte for intermediate temperature SOFC, but still shows rapid degradation during a long-term operation. In this study, CeO2 (1 mol%) as a stabilizer is partially substituted with lanthanum oxides (M2O3, M=Yb, Gd, Sm) to stabilize a cubic phase and thus durability in reducing atmosphere. 0.5M0.5Ce10ScSZ electrolytes were prepared by solid state reaction and sintered at 1450°C for 10 h to produce dense ceramic specimens. With addition of the lanthanum oxide, 0.5M0.5Ce10ScSZ showed lower degradation rates than 1Ce10ScSZ. Since Gd2O3 showed the highest ionic conductivity among the co-dopants, an electrolyte-supported cell with 0.5Gd0.5Ce10ScSZ was prepared to compare its longterm performance with that of 1Ce10ScSZ-based cell. Maximum power density of 0.5Gd0.5Ce10ScSZ-based cell was degraded by about 2.3% after 250 h, which was much lower than 1Ce10ScSZ-based cell (4.2%).