Oxygen isotope exchange with a dense La0.6Sr0.4CoO3-δ electrode on a Ce0.9Ca0.1O1.9 electrolyte

Oxygen isotope exchange experiments were carried out with a dense La(0.6)Sr(0.4)CoO(3-delta) film (0.5 mu m thick) deposited on a Ce(0.9)Ca(0.1)O(1.9) substrate by a laser ablation method. The isotope exchange profile was measured from the surface into the electrolyte by a secondary ion mass spectrometer (SIMS). The oxygen diffusion through the La(0.6)Sr(0.4)CoO(3-delta) film was fast enough not to make any observable gradient in oxygen isotope concentration inside the film. The surface isotope exchange rate, k*, was calculated from the diffusion profile into the electrolyte layer. The electrochemical impedance, sigma(E), was compared with k*. The oxygen partial pressure dependence of those two parameters were quite similar. The absolute value of k* was larger than expected from sigma(E) by a factor of 2 or higher. (C) 1999 Elsevier Science B.V. All rights reserved.