Influence of the electrode nature on conductivity measurements of gadolinia-doped ceria

Ten percent and 20% Gd-doped ceria ceramics were prepared by the oxalate coprecipitation method. The grain interior, grain boundary and total conductivities were determined by impedance spectroscopy using different contact electrodes. The purpose of this paper is to verify which contact material is the best in these studies and to determine the temperature range in which they can be used. Four different electrode materials were studied: platinum, gold and silver in the form of the commercial inks or paints and sputtered platinum. While the intragranular response is similar for all the electrode materials, the grain boundary semicircle on the complex plane impedance spectra is dependent upon the electrode nature, however, the activation energies are independent of the electrode nature. Our studies indicate that gold is suitable at temperatures below 800 degrees C, silver up to 700 degrees C, and sputtered platinum up to similar to 400 degrees C and that platinum ink can be used at higher temperatures when only the total electrolyte resistance is needed but gives poorly resolved grain boundary semicircles on the complex plane plots. (c) 2005 Elsevier B.V. All rights reserved.