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

Abstract Nano-sized Ce 0.8 Gd 0.2 O 2−δ and Ce 0.79 Gd 0.2 Cu 0.01 O 2−δ 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 Ce 0.8 Gd 0.2 O 2−δ and Ce 0.79 Gd 0.2 Cu 0.01 O 2−δ 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 °C in densification temperature of Ce 0.79 Gd 0.2 Cu 0.01 O 2−δ was obtained when compared with Ce 0.8 Gd 0.2 O 2−δ. The Ce 0.79 Gd 0.2 Cu 0.01 O 2−δ pellets sintered at 1000 °C and the Ce 0.8 Gd 0.2 O 2−δ sintered at 1400 °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−δ 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−δ shows much higher conductivity of 0.026 S cm −1 than Ce 0.8 Gd 0.2 O 2−δ (0.0065 S cm −1 ) at a testing temperature of 600 °C.