A SIMS study of oxygen tracer diffusion and surface exchange in La0.8Sr0.2MnO3+delta

The O-18/O-16 isotope exchange/depth profile (IEDP) method has been employe d to investigate oxygen tracer diffusion and surface exchange behaviour in the perovskite oxide La0.8Sr0.2MnO3+delta at temperatures between 700 degre es C and 1000 degrees C. The activation enthalpy for oxygen tracer diffusio n in the bulk (D-b*) was found to be 270 +/- 13 kT mol(-1), while that for oxygen tracer surface exchange (k(s)*) was 128 +/- 21 W mol(-1). Evidence o f short circuit diffusion was observed in all O-18 penetration profiles, an d this was ascribed to fast diffusion down grain boundaries. D-6* and k(s)* were also determined as a function of oxygen partial pressure at 1000 degr ees C: D-b* was found to vary according to P-O2(-0.41). the P-O2 dependence of k(s)* was unclear, as the O-18 penetration profiles at 1000 degrees C w ere diffusion-limited. (C) 2000 Elsevier Science B.V. All rights reserved.