Synthesis and sintering of Gd-doped CeO2 electrolytes with and without 1 at.% CuO dopping for solid oxide fuel cell applications

Nano-sized Ce0.8Gd0.2O2-delta and ce(0.79)Gd(0.2)Cu(0.01)O(2-delta) electrolyte powders were synthesized by the polyvinyl alcohol assisted combustion method, and then characterized by powder characteristics, sintering behaviors and electrical properties. The results demonstrate that the as-synthesized Ce0.8Gd0.2O2-delta and ce(0.79)Gd(0.2)Cu(0.01)O(2-delta) possessed similar powder characteristics, including cubic fluorite crystalline structure, porous foamy morphology and agglomerated secondary particles composed of gas cavities and primary nano crystals. Nevertheless, after ball-milling these two powders exhibited quite different sintering abilities. A significant reduction of about 400 degrees C in densification temperature of ce(0.79)Gd(0.2)Cu(0.01)O(2-delta) was obtained when compared with Ce0.8Gd0.2O2-delta. The ce(0.79)Gd(0.2)Cu(0.01)O(2-delta) pellets sintered at 1000 degrees C and the Ce0.8Gd0.2O2-delta sintered at 1400 degrees C exhibited relative densities of 96.33% and 95.7%, respectively. The sintering of ce(0.79)Gd(0.2)Cu(0.01)O(2-delta) was dominated by the liquid phase process, followed by the evaporation-condensation process, Moreover, ce(0.79)Gd(0.2)Cu(0.01)O(2-delta) shows much higher conductivity of 0.026 S cm(-1) than Ce0.8Gd0.2O2-delta (0.0065 S cm(-1)) at a testing temperature of 600 degrees C. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.