Thermoelectric properties of Co-doped n-type iron silicides prepared by mechanical alloying

N-type thermoelectrics of Co-doped iron silicide have been fabricated and studied. The Fe:Co ratio was kept constant at 0.95:0.05 to achieve a composition of (Fe_0.95Co_0.05)_x Si₂, where two values of x were chosen: 0.9 and 0.8 to observe the dispersion effect of the Si phase. For these, the mechanical alloying method for powdering and the pressure-resistance-sintering were employed. The sintering temperature, inherently controlling the size of dispersed Si phases, was varied from 760 to 880°C. The sintered specimens of the present process showed a similar Seebeck coefficient (a≈183 μV/K) compared to the ordinary ingot powdering method. The electrical and thermal conductivities, however, decreased with the reduction in interspacing of Si phases. The figure of merit was increased to Z=1.0×10^-4/K, which was believed to be enhanced by the phonon scattering effect of the dispersed Si phases