Processing of Samarium Doped Ceria for IT-SOFC. Grain Boundary Effect on the Electrical Conductivity

摘要

Nanometric powders of ceria doped with 10, 15 and 20% at. of samarium were prepared by a sol-gel method. The powders were compacted in cylindrical pellets and sintered at different temperatures in order to obtain grain sizes ranging from 1 to 10 microns. The electrical conductivity was measured in air by electrochemical impedance spectroscopy in the 1166 - 473 K temperature range. The bulk and grain boundary contributions to the overall conductivity were estimated by equivalent circuit analysis and the application of the brick layer model. While bulk conductivity values were markedly independent of the grain size, a relevant decrease in the grain boundary specific conductivity was observed for the finer grain samples in the lower dopant grade. For increased samarium content, this decrease in specific grain boundary conductivity with grain size becomes less relevant.