Effect of Grain Size on the Electrical Properties of Samaria-Doped Ceria Solid Electrolyte

Samaria-doped ceria (SDC) ceramic nanopowders have been synthesized by three different methods: co-precipitation, combustion, and hydrothermal. The Ce_0.8Sm_0.2O_1.9 nanopowder with an average aggregate size of 47 nm and crystallite size of 7–11 nm prepared by the hydrothermal method has been used for further consolidation by pressureless (PLS) and spark plasma (SPS) consolidation methods at 1000–1400 °C to obtain dense ceramic samples with different grain sizes in the wide range of 80 to 1500 nm. The total electrical conductivities of 0.010–0.015 S/cm at 600 °C were obtained for the PLS-derived samples. The dense SDC nanostructured ceramics consolidated by SPS showed the very low activation energy of only 0.66 eV at temperatures of 300–400 °C, and the total electrical conductivity of 0.0056 S/cm. The enhancement of the grain-boundary framework quality by annealing of the nano-SDC electrolyte at 1000 °C for 20 hours almost doubled the average grain size. In addition the electrical conductivity was enhanced almost 40%, while keeping the activation energy unchanged.