26Al tracer diffusion in titanium doped single crystalline α-Al2O3

Simultaneous 18O and 26Al tracer diffusion experiments were performed on titanium doped single crystalline α-Al2O3. The simultaneous tracer diffusion of 18O and 26Al clearly demonstrates that the aluminium diffusivity in Ti doped alumina is orders of magnitude higher than the oxygen diffusivity. The enhanced aluminium diffusivity is caused by an increase of the concentration of mobile Al vacancies. The reasonably good agreement between earlier conductivity measurements and our transport measurements indicates in accordance with theoretical work that the migration enthalpy of aluminium vacancies is (3.8 ± 0.1) eV.