The temperature dependence of volume diffusion coefficients of the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ tracer in single crystals of tungsten has been measured in the temperature range 1680–2270 K by a sectioning method of high depth resolution based on anodic oxidation of the specimen. The temperature dependence parameters are ${\mathit{D}}_0$=0.${16}_{\mathrm{-}0.08}^{+0.17\mathrm{}}$ ${\mathrm{cm}}^2$ ${\mathrm{s}}^{\mathrm{-}1}$ and Q=118.7±2.7 kcal/mole. An analysis of our data shows that the diffusion of cobalt in single crystals of tungsten is ‘‘normal’’ and obeys the same regularities as diffusion of tungsten-series impurities in tungsten, for which the diffusion mechanism by monovacancies is well established [N. K. Archipova et al., Phys. Rev. B 30, 1788 (1984)]. Systematic errors in the determination of volume diffusion coefficients have been discussed. They arise when (i) one uses a low-resolution sectioning method and (ii) one does not take into account the complexity of diffusion fluxes occurring near the external surface of real crystals.

• Received 16 March 1992

DOI:https://doi.org/10.1103/PhysRevB.46.2831