Abstract
The effects of Ti, Zr and Nb addition on the thermoelectric properties of β-FeSi2 were investigated. Mixture of Fe and Si powders with composition of Fe1-xSi2 was arc-melted in an argon atmosphere to form a button composed of α-Fe2Si5 and ε-FeSi phases. The button was ground under -60mesh and Ti, Zr or Nb powders were mixed for Fe1-xMxSi2(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-FeSi2 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 FeSi2, 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-FeSi2. 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(Q2/ρ) of β-FeSi2, especially at high temperatures. On the other hand, since the increase in thermal conductivity(K) by Zr addition was not apparent, figure of merit(Q2/ρK) of, B -FeSi2 increased with increasing Zr addition and showed the same tendency as the power factor. EPMA and XRD revealed that Fel.xMxSi2 (M=Ti, Zr, Nb) was composed of β-FeSi2 matrix with dispersion of TiSi2, ZrSi2 or NbSi2 particles.
