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

Fine Ce_0.8Sm_0.2O_1.9 (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 °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 °C exhibit an excellent total ionic conductivity of 0.082 S cm⁻¹ at 800 °C in air. However, when measured in an N₂ + 33.3%H₂ 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 temperatures above 550 °C, due to the introduction of a mixed Ce⁴⁺/Ce³⁺ valence state and the generation of the electronic conduction in the reducing atmosphere.