The effects of Ti, Zr and Nb addition on the thermoelectric properties of β-FeSi
2 were investigated. Mixture of Fe and Si powders with composition of Fe
1-xSi
2 was arc-melted in an argon atmosphere to form a button composed of α-Fe
2Si
5 and ε-FeSi phases. The button was ground under -60mesh and Ti, Zr or Nb powders were mixed for Fe
1-xMxSi
2(M=Ti, Zr, Nb, 0≤X≤1.8). Then, the mixed powders were groun(MA) in a vibrational mill (SPEX-8000) for 36 ks. β-FeSi
2 phase was not formed during MA, but was obtained by hot pressing of MA powders at 1173 K for 1.8 ks under 25MPa. It was found that Zr addition drastically changed the thermoelectric properties of FeSi
2, especially the temperature dependence of resistivity and thermoelectric power, while addition of Ti and Nb showed rather deleterious effect on the thermoelectric properties of β-FeSi
2. Zr addition extremely decreased the resistivity(ρ), although thermoelectric power(Q) decreased with increasing Zr addition. As the result, Zr addition increased the power factor(Q
2/ρ) of β-FeSi
2, especially at high temperatures. On the other hand, since the increase in thermal conductivity(K) by Zr addition was not apparent, figure of merit(Q
2/ρK) of, B -FeSi
2 increased with increasing Zr addition and showed the same tendency as the power factor. EPMA and XRD revealed that Fel.xMxSi
2 (M=Ti, Zr, Nb) was composed of β-FeSi
2 matrix with dispersion of TiSi
2, ZrSi
2 or NbSi
2 particles.
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