Effects of Ti, Nb and Zr doping on thermoelectric performance of β-FeSi2

The effects of Ti, Nb and Zr doping on the thermoelectric performance of a hot-pressed beta -FeSi2 were investigated. Ti doping did not have a significant influence on the thermoelectric properties. Nb doping decreased the electrical resistivity over the entire temperature range. The thermoelectric power of the Nb-doped samples showed lower values below 800 K and higher values above this temperature than those of the non-doped sample. The figure of mel it of the Nb-doped samples showed higher values in a high temperature range as compared to the non-doped sample. In the case of the Zr-doped samples. the the thermoelectric power was markedly deteriorated below 900 K. In contrast, in the higher temperature range, the thermoelectric power was enhanced by Zr-doping. The electrical resistivity was significantly decreased by Zr doping. The hot-pressed Fe0.94Zr0.06Si2 showed around 20 mu Omegam over the entire temperature range. These values of electrical resistivity are extremely low as compared to the beta -FeSi2 doped with other elements, particularly in a low temperature range. The figure of merit for the Zr-doped samples was significantly enhanced in a high temperature range. The maximum figure of merit, 0.67x10(-5)/K, was obtained at 1064 K for Fe0.94Zr0.06Si2, which was ten times larger than that of the non-doped sample at the same temperature. Thus, it is evident that Zr doping is quite effective for enhancement of the performance of beta -FeSi2, in a high temperature range. (C) 2001 Elsevier Science B.V. All rights reserved.