DETERMINATION OF DIFFERENT OXYGEN-TRANSPORT MECHANISMS AND MEASUREMENT OF THE OXYGEN ION CONDUCTIVITY OF Y1BA2CU3O7-X

By undertaking AC electrochemical impedance experiments on yttria stabilised zirconia electrolytes with polished Y1Ba2Cu3O7-x electrodes, the activation energy for oxygen ion transport within the bulk of Y1Ba2Cu3O7-x, in air, over the temperature range 823 K-1043 K, was determined to be 1.50 +/- 0.05 eV. At 1000 K the oxygen ionic conductivity was calculated to be around one order of magnitude lower than that in yttria stabilised zirconia. Typical calculated values were sigma = 5 x 10(-5) (OMEGA-cm-1) and 6 x 10(-3) (OMEGA-cm)-1 at the respective temperatures 823 K and 1043 K. By employing a similar cell but with Y1Ba2Cu3O7-x paste electrodes, oxygen transfer between the Y1Ba2Cu3O7-x and the electrolyte was found to occur via a surface diffusional process. Over the temperature range 873 K-1098 K, in air, the activation energy for in-diffusion at the surface was found to be 1.4 +/- 0.1 eV and that for out-diffusion at the surface to be 1.76 +/- 0.05 eV.