δ₁-Zn pseudo-binary couples were annealed at 325 to 408°C. The ζ phase layers formed in those couples had the concentration range from 6.8 to 7.2 at% Fe. The temperature dependence of the diffusion coefficients in the ζ phase layers was given by the following equation:
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In previous work we obtained the diffusion coefficients in the initial ζ phase layers which appeared prior to the formation of the δ₁ and Γ phase layers in Fe-Zn binary couples. In this paper the diffusion coefficients of the initial ζ phases were also measured more accurately at temperatures from 240 to 322°C. The temperature dependence of the diffusion coefficients in the initial ζ phase layers having a constant concentration range from 6.8 to 9.9 at% Fe was given by the following equation:
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Kirkendall markers in both types of the couples existed always at the interfaces between the ζ phase layers and the Zn couple halves. The presence of such a pronounced Kirkendall effect means that there is a one-sided diffusion of Zn atoms by the vacancy mechanism. The difference in activation energy between the above two equations is probably due to the concentration difference of the non-equilibrium vacancies.