Electrical characterization of thermomechanically stable YSZ membranes for micro solid oxide fuel cells applications

Yttria-stabilized zirconia free-standing membranes were fabricated by pulsed laser deposition on Si/SiO2/Si3N4 structures for developing silicon-based micro devices for micro solid oxide fuel cell applications. Their mechanical stability under working conditions was evaluated satisfactorily by applying thermal cycling to the membranes. Membranes mechanically stable at operating temperatures as high as 700 °C were obtained for deposition temperatures in the range between 400 and 700 °C. Thermomechanical behavior as measured by X-ray microdiffraction was correlated with the evolution of the microstructure with the temperature from TEM analysis, comparing as-deposited and post-deposition annealed membranes. Electrical properties of both yttria-stabilized zirconia films and membranes were studied by DC conductivity and impedance spectroscopy, respectively. A difference of almost one order of magnitude was measured between bulk and stressed films while conductivities close to the bulk were observed for YSZ membranes. Values of area specific resistance of 0.15 Ωcm2 were measured at temperatures below 450 °C for 240 nm thick YSZ membranes deposited at 600 °C and annealed at the same temperature for 2.5 h.