Abstract. Yttria-doped zirconia nanopowders have been obtained using the hydrothermal procedure starting from soluble inorganic salts. The mechanisms and kinetics of the process have been studied to obtain high purity powders with a crystalline size range of 4 to 22nm and specific surface near 200 m 2 /g. These powders have been have been used to obtain membranes with controlled thickness and with densities over 95% of the theoretical value by employing the tape casting technique using organic binders, dispersants and surfactants. The influence of the additives and sintering regime on the density and microstructure of membranes has been studied. The ionic conductivity of the materials was investigated and modelled. Different types of ruthenate pastes were used to obtain thick resistive films on the zirconia membranes and interactions between the substrate and membranes were studied. Finally the gauge characteristics of the device and possibilities for applications as mechanical pressure sensors with high sensitivity are discussed.Introduction.

Impedance Spectroscopy (IS) is considered one of the most popular methods to the characterization of ceramic materials used as electrolytes for fuel cells, such as, solid oxide fuel cells (SOFCs) and intermediate temperature -solid oxide fuel cells (IT-SOFCs). However, experimental data analysis requires developing a model describing the electrical behavior of the solid electrolyte.The aim of this paper is to characterize the electrical behavior of sintered composite based on ceria using a new model. Therefore, the measurements of impedance components (Z ' and Z '' ), of two composites based on ceria, designed to be used as solid electrolytes for intermediate temperature fuel cells (IT-SOFC) were performed by Impedance Spectroscopy (IS). The materials are two different composites based on ceria 10YDC + (10%) 150ppm YA (E1) and 10ScDC + (10%) 150ppm YA (E2), obtained by sol-gel method and sintered at temperature of 1500 0 C. Two models (microstructural and electric) were applied for determining the electrical conductivity and permittivity of grains ( g and rg ) and grain boundaries ( gb and rgb ) values and the components of the complex impedance Z (Z ' and Z '' ) at different frequencies. The composite E1 presents better conductivities ( g and gb ) than E2 and it is favorable for use as solid electrolyte fuel cells.

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