Diffusion Processes at the MnSi 1.75 /Cr Contact

Diffusion processes between chromium and the higher manganese silicide MnSi 1.75 in MnSi 1.75 /Cr and MnSi 1.75 /Cr/Ni contact regions are studied by microstructural analysis and x-ray microanalysis. The results demonstrate that, at elevated temperatures, the composition and sequence of layers in the diffusion zone between MnSi 1.75 and Cr are consistent with the phase equilibria in the Cr–Mn–Si system. In MnSi 1.75 /Cr/Ni samples, a larger portion of the diffusion zone between MnSi 1.75 and Cr consists of several Mn–Ni–Si phases and only one Cr–Mn–Si phase. The intermetallic phases forming in the diffusion zones exhibit metallic conduction and high thermal conductivity, which makes it possible to reduce energy losses in the hot junctions of thermoelements at the interface between an MnSi 1.75 -based thermoelectric material and metal. It is shown that the use of chromium as a diffusion-impervious layer in MnSi 1.75 /Cr/Ni contacts not only slows down Ni diffusion in MnSi 1.75 but also improves the mechanical properties of the contact.