Isotope effect in niobium self-diffusion

Measurements of the isotope effect in niobium self-diffusion have been made over the temperature range 1900 °C to near the melting point (2468 °C). The measurements were made by simultaneous diffusion of ${}_{}{}^{95}{}_{}{}^{}\mathrm{Nb}$ and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Nb}$ isotopes from a thin surface layer and subsequent sectioning. The ratio of ${}_{}{}^{92}{}_{}{}^{}\mathrm{Nb}$ to ${}_{}{}^{95}{}_{}{}^{}\mathrm{Nb}$ in each section was determined using a well-type Ge(Li) detector of high efficiency. The low values of the measured isotope effect are similar to other bcc metals (Na, $\alpha$- and $\delta -\mathrm{F}\mathrm{e},\mathrm{C}\mathrm{r}$, and $\beta -\mathrm{Z}\mathrm{r}$); however, the temperature dependence is different.