Synthesis and electrical properties of Ce0.8Sm0.2O1.9 ceramics for IT-SOFC electrolytes by urea-combustion technique

Fine Ce0.8Sm0.2O1.9 (SDC) powders with a fluorite cubic phase were prepared using a urea-combustion technique. The sinterability and microstructural evolution of the resulting ceramics were investigated. The results indicate that the ceramics sintered above 1350 degrees C display relative densities of about 98.5% along with significant grain growth. With respect to their electrical conduction properties, the specimens sintered above 1350 degrees C exhibit an excellent total ionic conductivity of 0.082 S cm(-1) at 800 degrees C in air. However, when measured in an N-2 + 33.3%H-2 atmosphere, a pronounced Warburg feature appears in the impedance plots of the SDC ceramics, together with a significant increase of the total conductivity at measuring temperaures above 550 degrees C, due to the introduction of a mixed Ce4+/Ce3+ valence state and the generation of the electronic conduction in the reducing atmosphere. (C) 2008 Elsevier L.td and Techna Group S.r.l. All rights reserved.