Low resistance of C/C-SiC composites against oxidation at high temperatures created the need to develop materials that could be used as oxygen protective layers. Yttrium silicate (Y2SiO5) has been proposed as an excellent candidate for this purpose. In order to investigate whether Y2SiO5 is a sufficient barrier against oxygen, the transport parameters of oxygen in this material should be determined. In the present study, O-18(2) tracer diffusion experiments have been conducted in the temperature range between 1000 degrees C and 1300 degrees C. Secondary ion mass spectrometry (SIMS) was used to determine tracer diffusivities D* and oxygen incorporation rates k* in undoped and in 03 at.% praseodymium doped yttrium silicate. Activation enthalpies E-A(D*) and E-A(k*) were determined. An indication of anisotropic oxygen diffusion in yttrium silicate has been found. (C) 2014 Elsevier B.V. All rights reserved.