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Characterization of YSZ-SDC electrolytes obtain with nanometric powders prepared by combustion

Abstract:

8% Yttria doped zirconia, 20% samaria doped ceria and a mixture YSZ-SDC (25-75%w/w) were prepared by combustion method. Powders were sintered in pellets at 1350 °C to obtain dense material. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) were used for phases, microstructural and ionic conductivity measures. The samples exhibit a fluorite type structure with nanometric sized particles. XRD analysis indicate SDC and solid solution coexisting in the mixed sample. SEM micrograph shows microstructure with grain sizes in the range of 0,5 to 1,0 μm. SDC shows good densification, showing the higher ionic conductivity below 600 °C, with an activation energy of 1,06 eV. Above 600 °C, there was a decrease in the conductivity attributed to a high concentration of dopant that could promote the defect association, limiting the movement of oxygen vacancies. This effect was reduced by mixing with YSZ, showing a lower activation energy (0,84 eV), which may be related to local composition change due to the formation of a solid solution.