Polarization behavior of yttrium barium copper oxide electrodes on yttria-stabilized zirconia electrolytes

YBa2Cu3O7-x (YBCO) was evaluated as a potential electrode material for yttria stabilized zirconia (YSZ) based electrochemical devices, due to its high electronic conductivity and capability for oxide ion transport. YBCO electrodes were deposited by screen-printing, which requires moderately high firing temperatures to assure a good bonding and mechanical stability of the deposited layers. Unfortunately, chemical reactivity towards the YSZ electrolyte may significantly decrease electrode performance. In addition, electrochemical decomposition of YBa2Cu3O7-x was observed at fairly low current densities (almost-equal-to 20 mA/cm2). Overpotentials increased as electrode firing temperature increased from 920 to 940-degrees-C due to electrode densification. At 960-degrees-C, the onset of chemical degradation was observed but overpotential losses were lowest for these firing conditions. Microstructural examination indicated that partial degradation during sintering had allowed a more porous microstructure to develop at 960-degrees-C.