For applications in high temperature fast conductometric gas sensors and oxygen membranes, several mixed conductors show promising features. In particular, acceptor-doped strontium titanate (STO) has been widely investigated for an application as a fast conductometric oxygen sensor. By a B-site substitution with 35% iron, the resulting ceramic solid solution SrTi0.65Fe0.35O3 (STF35) exhibits a temperature-independent conductivity, an ideal prerequisite for a gas sensor. In the presented study, the oxygen tracer exchange behavior and the tracer diffusion of dense ceramic STF35 bulks have been investigated in the temperature range between 600 and 900 degrees C by means of O-18(2) tracer exchange experiments and subsequent secondary ion mass spectrometry (SIMS), resulting in the determination of k* and D* values, respectively. Furthermore, by coating the samples with a thin alkaline earth metal oxide layer (CaO). a significantly enhanced oxygen surface exchange reaction was observed. These findings are in good agreement with previous results on STO single crystals. (C) 2010 Elsevier B.V. All rights reserved.