Niobium self-diffusion

The diffusion of ${}_{}{}^{95}{}_{}{}^{}\mathrm{Nb}$ in niobium has been measured between 1353 and 2693 K. The data showed nonlinear Arrhenius behavior and fit the expression $D=[8\mathrm{}\times {10}^{-3\mathrm{}}\exp (-3.62\mathrm{} \mathrm{eV}/\mathrm{kT})+3.7\mathrm{}\exp (-4.54\mathrm{} \mathrm{eV}/\mathrm{kT}\left)\right]$ ${\mathrm{cm}}^2$ ${\sec }^{-1\mathrm{}}$. The data are interpreted in terms of a single-vacancy-divacancy mechanism. The effect of oxygen on niobium self-diffusion was measured over the temperature range 1750-2690 K. There was no measurable difference in the diffusion coefficient obtained from samples with 500-wt-ppm ${\mathrm{O}}_2$ and samples with less than 10-wt-ppm ${\mathrm{O}}_2$.