Grain growth kinetics and its impact on the conductivities of Ce_0.9Gd_0.1-xCa_xO_2-δ electrolyte: Average time effect and migration energy

Gadolinium and calcium co-doped ceria-based electrolyte (GCDC) is synthesized by the co-precipitation method and grain growth behavior and its effect on the electrical conductivity are investigated. Sintering behavior results suggest that the co-doped electrolyte could be densified below 1400°C. Grain growth exponents are 6, 4, 4, 3 when the calcium doping content is 0 mol%, 0.5 mol%, 1 mol% and 2 mol%, respectively. The grain growth behavior is further elucidated through the “Average time effect” proposed in this study. Meanwhile, the electrical conductivity is 0.041 S/cm for 0.5 mol% Ca doped GDC electrolyte, which is 10 % higher than that at 0 mol% doping. The space charge potential is 0.15 V and 0.19 V for 0.5 mol% dopant and 0 mol% dopant, respectively. The specific grain boundary conductivity of the 0.5 mol% doped electrolyte exhibits a positive correlation as a function of grain size and temperature, while its total conductivity exhibits a parabolic law. This phenomenon is finally interpreted by the “Migration energy” proposed in this work.