Oxygen surface exchange on gadolinia doped ceria

The majority of work on the oxygen ion transport properties of electrolyte materials has been undertaken using AC impedance spectroscopy or other elec trical techniques. In general, these techniques are excellent methods for m easuring the oxygen mobility of materials, such as gadolinia-doped ceria (C GO), due to their negligible electronic conductivity. However, it is also u seful to measure the oxygen ion diffusivity of materials directly using ins truments such as secondary ion mass spectrometers (SIMS) to verify these co nductivity results. The added advantage of a technique such as SIMS is that it also provides data on the kinetics of oxygen exchange on the surface of the material as well as the oxygen diffusion in the bulk. However, there i s very little work published to date on the measurement of oxygen ion diffu sivity using SIMS on this type of electrolyte material. This paper will con centrate on the oxygen diffusion and oxygen surface exchange behaviour of C e0.9Gd0.1O1.95 measured by isotope exchange and SIMS. Data will be presente d for the dependence of the tracer diffusion coefficient, DT, and the oxyge n surface exchange coefficient, k, both as functions of temperature and oxy gen partial pressure, P-O2. These results will provide the basis for determ ining the mechanism for the incorporation of oxygen into these materials. ( C) 2000 Elsevier Science B.V. All rights reserved.