Thermoelectric properties of Fe3Si with the DO3 structure
where some Fe were replaced with Mn and V were examined. By adding
5 mol% Mn or V, the Seebeck coefficients, alpha, reach the maximum values of
about +22.5 micro V/K, while they decreased to a large negative value by the
further replacement of Fe by these transition elements. The minimum values of
alpha were -36 micro V/K and -45 micro V/K at Fe-30 mol%Mn-25 mol%Si and
Fe-20 mol%V-25 mol%Si, respectively. These values are smaller than the minimum
value reported for the iron-based alloys. The compositional dependency of
alpha corresponds to the fact that the added transition metal atoms replaced
iron atoms at a particular site in the DO3 lattice. By combining
an approximate model approximation suitable for simple metals and the density of
state reported, however, the obtained compositional dependency of
thermoelectricity could not be explained. The absolute values of alpha in the
Fe-Mn-Si system were small, both in the samples with the alpha-Fe solid
solution and with the gamma-Fe solid solution.