Fabrication and electrochemical characterization of planar Pt-CGO microstructures

Dense, nanocrystalline gadolinia doped ceria (CGO) thin films were prepared by sputtering on a variety of substrates. The CGO films were electrochemically characterized with the aid of interdigitated Pt electrodes by impedance spectroscopy as a function of operating temperature (175 - 340 degrees C) CGO film thickness (157, 233, 315 nm), deposition temperature (room temperature, 300, 500 degrees C), and Pt electrode pattern geometry (line pattern spacing 10, 15, 25, 50, 100 pm). The different parameter variations enabled the identification of five contributions to the impedance spectra attributed, respectively, to wiring and contacts, grain, grain boundary, current constriction at the triple phase boundary, and electrode effects. The ionic conductivity of the CGO films were characterized by the expression sigma=(A/T)exp( - E-A/kT), with A=10(8.66 +/- 0.72) Scm(-1)K and EA=0.97 +/- 0.07 eV with magnitude higher than values reported for both bulk and thin film CGO previously reported in the literature. The electrochemical impedance of the Pt electrodes was found to decrease markedly for CGO films grown at reduced temperatures. Explanations for these observations are presented. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.