Diffusion of cobalt, silver, and gold in praseodymium

The thin-layer lathe-sectioning technique has been used to measure the solute diffusivities of cobalt, silver, and gold in dhcp and bcc praseodymium. The diffusivities in the bcc phase can be described D_Ag=3. 2×10^-2 exp(-21 500/RT) and D_Au=3.3×10 ^-2 exp(-20 100/RT) cm²/sec. In polycrystalline samples the average of the diffusivities along the two axes of dhcp praseodymium can be expressed by D_Co=4.7×10^-2 exp(-16 400/RT), D _Ag=1.4×10^-1 exp(-25 400/RT), and D _Au=4.3×10^-2 exp(-19 700/RT) cm²/sec. These diffusivities are substantially higher than the self-diffusion coefficients of praseodymium. The change in the crystalline structure of the matrix affects only slightly the solute diffusivities, contrary to its effect on the self-diffusion coefficients. The remarkable similarity of these results with those concerning the solute diffusion of noble metals in Group III-B and IV-B metals, suggests that the same diffusion mechanism by interstitials operates in both cases.