Electrochemical characterization of thin films for a micro-solid oxide fuel cell

One of the first technological benchmarks towards the realization of a micro solid oxide fuel cell is the production of thin film structures with adequate electrochemical properties. This paper describes the deposition of thin film yttria-stabilized zirconia electrolytes and lithographically patterned platinum and gold electrodes. By using conventional, ultraviolet lithography, electrode patterns were produced with features sizes as fine as 15 Am, enabling a more direct investigation into the role of the triple phase boundary. Impedance spectroscopy measurements show three arcs, ascribed to the grain, grain boundary and electrode processes, and an offset on the real axis due to the leads. The high frequency arc, ascribed to the ohmic resistance of the YSZ electrolyte, exhibited an activation energy of 1.0 eV, while the intermediate frequency arc, attributed to blocking grain boundaries, exhibited an activation energy of 0.69 eV. The low frequency, non-ohmic arc was found to be highly dependent upon the electrode material and exhibited activation energies of 0.91 eV for gold electrodes and 0.77 eV for platinum electrodes. The electrode impedances for different sample geometries were similar when normalized to the triple phase boundary length.