The Effect of Co and Ni Doping on the Thermoelectric Properties of Sintered .BETA.-FeSi2.

The sintered β-FeSi2 compacts doped with Co and Ni(Fe1-x-yCoxNiySi2, x=0-0.03, y=0-0.04) were prepared by mechanical alloying for 10h and hot-pressing for 30min at 1173K. The effects of Co and Ni doping on the structure and thermoelectric properties of β-FeSi2 have been studied by X-ray diffraction analysis and measurements of electrical resistivity and thermoelectric power. The results obtained are summarized as follows:1) The electrical resistivity decreased with increasing Co and Ni doping, but the decreasing ratio in resistivity was larger in Co doping than in Ni doping. This is due to the larger solubility of Co than that of Ni in β-FeSi2.2) All of the sintered β-FeSi2 compacts doped with Co and Ni were n-type semiconductors. The thermoelectric power increased with increasing Co and Ni doping, but over doping caused decreasing of thermoelectric power. Maximum thermoelectric power was obtained by doping with Co:x=0.01 and Ni:y=0.01.3) Co doping was more effective for increasing power factor than Ni doping, but small amount of Ni doping with Co further increased power factor. Maximum power factor was obtained by simultaneous doping with Co:x=0.03 and Ni:y-0.01.