Diffusion of Cobalt, Silver, and Gold in Praseodymium

Abstract

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.