Two ScYSZ electrolytes with different impurity levels were evaluated by electrochemical impedance spectroscopy using a nickel point electrode setup. The nickel electrodes showed lower electrode polarization resistances on the pure electrolyte than on the impure electrolyte. Time-of-flight secondary ion mass spectrometry was used to evaluate the electrode/electrolyte interfaces. Stronger signals from silica impurities in the electrode/electrolyte interface, relative to the electrolyte/gas interface, were found on the impure electrolyte than on the pure electrolyte. (C) 2007 Elsevier B.V. All rights reserved.