HIGH-TEMPERATURE OXYGEN-TRANSPORT AND ELECTROCHEMICAL-BEHAVIOR OF YBA2CU3OX

In this preliminary study, the high temperature oxygen transport and electrochemical behavior of YBa2Cu3Ox was evaluated in a solid-state electrochemical cell employing a yttria-stabilized zirconia (YSZ) solid electrolyte. The oxygen chemical diffusion coefficient was measured by a solid-state potentiostatic step technique and found to be 5 x 10(-8) cm2/s at 800-degrees-C. The dc polarization behavior of YBa2Cu3Ox electrodes deposited on YSZ electrolyte was governed primarily by an ohmic process in oxygen, air, and He environments in both the anodic and cathodic directions. The frequency dispersion of the electrochemical response obtained by ac impedance spectroscopy showed two depressed circular arcs in complex plane plots that are off set from the origin, indicative of a resistive path in the equivalent circuit model at high frequencies. It is proposed that the YBa2Cu3Ox electrode poses the major impedance to the overall rate and dominates the electrochemical performance of the cell.