β-FeSi_2の熱電特性に及ぼすTi, ZrおよびNb添加の影響 [in Japanese] Effect of Ti, Zr and Nb Addition on Thermoelectric Properties of β-FeSi_2 [in Japanese]
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The effects of Ti, Zr and Nb addition on the thermoelectric properties of β-FeSi<SUB>2</SUB> were investigated. Mixture of Fe and Si powders with composition of Fe<SUB>1</SUB>-xSi<SUB>2</SUB> was arc-melted in an argon atmosphere to form a button composed of α-Fe<SUB>2</SUB>Si<SUB>5</SUB> and ε-FeSi phases. The button was ground under -60mesh and Ti, Zr or Nb powders were mixed for Fe<SUB>1</SUB>-xMxSi<SUB>2</SUB>(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<SUB>2</SUB> 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<SUB>2</SUB>, 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<SUB>2</SUB>. 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<SUP>2</SUP>/ρ) of β-FeSi<SUB>2</SUB>, 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<SUP>2</SUP>/ρK) of, B -FeSi<SUB>2</SUB> increased with increasing Zr addition and showed the same tendency as the power factor. EPMA and XRD revealed that Fel.xMxSi<SUB>2</SUB> (M=Ti, Zr, Nb) was composed of β-FeSi<SUB>2</SUB> matrix with dispersion of TiSi<SUB>2</SUB>, ZrSi<SUB>2</SUB> or NbSi<SUB>2</SUB> particles.
- J. Jpn. Soc. Powder Powder Metallurgy
J. Jpn. Soc. Powder Powder Metallurgy 44(1), 34-38, 1997-01-15
Japan Society of Powder and Powder Metallurgy