Cation Tracer Diffusion in Cr 2 O 3 and Cr 2 O 3‐0.09 wt% Y 2 O 3

The cation diffusivities in the lattice and along dislocations and grain boundaries have been measured on sintered polycrysals of Cr 2 O 3 ; and Cr 2 Cr 2 O 3 ‐0.09 wt% Y 2 O 3 at1100°C and at the pO 2 corresponding to that of Cr/Cr 2 O 3 equilibrium at that temperature. Results for lattice and dislocation diffusivities in pure Cr 2 O 3 are in good agreement with previous work. The present results indicate that yttrium additions have negligible effect on lattice and dislocation diffusion. However, grain‐boundary diffusion in pure Cr 2 O 3 is significantly slower than grain‐boundary diffusion in Cr 2 O 3 ‐0.09 wt% Y 2 O 3 . The results are discussed in terms of their implications for the reactive‐element effect in high‐temperature oxidation of chromium‐containing alloys.