Anodic polarization related to the ionic conductivity of zirconia at Ni-zirconia/zirconia electrodes

To clarify the extension of the triple phase boundary (TPB), which directly affects the electrode polarization behavior, in the cermet layer of the Ni-zirconia anode, we studied the anodic polarization properties of four types of Ni-zirconia cermets (Ni-0YZC Ni-3YZC, and Ni-8YZC) on three types of zirconia electrolytes (3YZE, 5YZE, and 8YZE). Based on impedance spectroscopy and current interruption measurements, the overall interfacial conductivity, 1/R-i was analyzed by dividing it into two increments: conductivity due to the TPB at the surface of the electrolyte, (1/R-i)(2D), and that due to the active TPB inside the cermet, (1/R-i)(3D). It was found that (1/R-i)(2D) shows a slight dependence, on the order of about 0.3, on the conductivity of the electrolyte. On the other hand, (1/R-i)(3D) depended on the ionic conductivity of the zirconia in the cermet on the order of about 1.3. These results were explained by the theory deduced for the case that the active TPB expanded into the cermet layer. (C) 2001 The Electrochemical Society.