Diffusion in the B20-type phase FeSi

Self-diffusion of Fe and impurity diffusion of Ge in the B20 phase FeSi have been studied as a function of temperature using the radiotracer method with isotopes 59Fe and 71Ge. 71Ge has been used to simulate Si self-diffusion. Both diffusivities are very small, and their values for Fe are about one to two orders of magnitude smaller than for Ge. This uncoupled diffusion may be explained by vacancy-based diffusion on the Fe and Si sublattice. Both diffusivities reach a value of about D(T M) ≈ 10−14m2s−1 at T M = 1683 K. which is more typical for semiconductors than for metals. Results are discussed in comparison with other diffusion data on phases of the Fe-Si system and on other transition metal silicides.