The oxygen surface exchange coefficient (k) and the self‐diffusion coefficient (D*) of (CGO) have been measured using the isotopic exchange, depth profiling (IEDP) method using a secondary ion mass spectrometer (SIMS). At 486°C, D* was of the order of and k was . This D* is comparable with values calculated from ac impedance spectroscopy data. particles on the surface of the CGO give rise to a 100‐fold increase in k at 500°C. A comparison of impedance spectroscopy results on CGO with platinum electrodes and LSFC electrodes is given, and the different electrical responses are discussed.