Study of Sm_(0.2)Ce_(0.8)O_(1.9)(SDC) electrolyte prepared by a simple modified solid-state method

Sm0.2Ce0.8O1.9 （SDC） electrolyte was prepared by a modified solid state method at relatively low sintering temperatures without any sintering promoters. The phase composition and microstructure of the electrolytes were investigated by X-ray diffraction （XRD） and field emission scanning electron microscopy （FESEM） technologies. A relative density of SDC electrolyte sintered at 1300 ℃ reached 97.3%and the mean SDC grain size was about 770 nm. Their ionic conductivity and thermal expansion coefficient were also measured by electrochemical workstation and dilatometer. The electrolyte attained a high conductivity of 5×10^-2 S/cm at 800 ℃ with an activation energy of 1.03 eV and a proper thermal expansion coefficient of 12.6×10^-6 K^-1.

Preparation and characterization of SDC nanorods/LNC nanocomposite electrolyte

The nanocomposite electrolytes composed of Smo.2Ce0.801.9 （SDC） nanorods enclosed by { 110} and { 100} facets and a binary carbonate （（Lio.52Nao.48）2CO3, LNC） were prepared by a wet mixing method to investigate the conduction mechanism. The X-ray diffraction （XRD）, scanning electron microscopy （FESEM） and transmission electron microscopy （TEM） techniques were em- ployed to characterize the phase components and microstructures of SDC nanorods and SDC nanorods/LNC composite electrolytes. X-ray powder diffraction showed that a well-cubic fluorite structure was formed. The AC impedance spectroscopy and DC polariza- tion method were used to measure the electrical conductivities of nanocomposite electrolytes under different conditions. The overall ionic conductivities of nanocomposite electrolytes in the air and hydrogen atmospheres were measured up to 82 and 96 mS/cm at 650 ℃, respectively. Additionally, the protonic and oxide ionic conductivities of nanocomposite electrolytes were found to reach 20 and 18 mS/cm at 650 ℃, respectively. The conduction mechanism was discussed in detail by comparing the conductivities of nanocom- posite electrolytes. The protonic conductivity of SDC nanorods/LNC nanocomposite was higher than oxide ionic conductivity. The melt of LNC and the interface layer may make a dominant contribution to oxide ions and protonic conductivity in air and hydrogen atmosphere, respectively.