Electrical properties of samaria-doped ceria electrolytes from highly active powders

The correlations of the microstructures and the electrical properties of high reactive Ce_0.8Sm_0.2O_1.9 (SDC) powders, synthesized via an optimal carbonate coprecipitation method, were investigated. Microstructure of the SDC ceramics sintered at 900-1400 °C showed uniform grain and small grain size, compared with those prepared with various methods under similar sintering conditions. These features may be related to high conductivity (σ_{600 °C} = 0.022 S cm^-1) and low activation energy for conduction (0.66 eV). AC impedance spectra were involved to resolve grain interior and grain boundary resistance. Grain boundary contribution to the total resistance showed the values below 1/2 at 200-450 °C, suggesting low grain boundary effect. The motion enthalpy for the grain interior conduction decreased while the association enthalpy increased with sintering temperature up to 1300 °C, which might be possibly originated from the increase in lattice parameters with the sintering temperature.