Effect of powder treatment by mechanofusion process on thermoelectric properties of FeSi2 system

The thermoelectric properties of hot-pressed Fe_0.91Mn _0.09Si₂ (mean diameter:D,=5-10 μm) were measured with changing the powder treatment. In order to improve the thermal conductivity and the electrical conductivity, carbon (0, 1 and 2 wt%, D_m=0.02-0.3 μm) was added and the mechanofusion process was used. The mechanofusion process can produce composite powders with high shear stress and compressive force, allowing a more homogeneous compact to be fabricated. As a result, the thermal conductivity was remarkably improved in this system. EPMA analyses showed that extremely fine particles of carbon were dispersed along grain boundaries without aggregation. However, the electrical conductivity decreased in this case. This is probably because the electrical resistivity of carbon black is very high. However, when graphite are added, the MF process would be very effective to improve the figure of merit, because the process can increase the grain boundary with additives and improves the electrical conductivity