Thermoelectric Properties of β-Fe1-xCoxSi2 Semiconductors

Abstract

The thermoelectric properties of Co-substituted β-FeSi2 (Fe1-xCoxSi2, 0.00≦x≦0.10) have been characterized by Hall effect measurements at 300 K and by measurements of electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) between 300 and 1150 K. Fe1-xCoxSi2 samples are n-type in the measured temperature range. The electrical resistivity, Seebeck coefficient, and thermal conductivity are strongly affected by the Co substituting concentration (x). For the composition 0.00≦x≦0.05, κ decreases with increasing temperature, reaches a minimum, and increases. At x=0.10, the κ increases monotonically with increasing temperature. From the composition and temperature dependences of κ, it was found that the thermal conductivity of the lattice component κph is dominant in Fe1-xCoxSi2 semiconductors. At low temperatures, κph can be explained by the presence of small polarons. At x=0.05, the power factor (P=S2/ρ) as well as the dimensionless figure of merit (ZT) shows a maximum value of 1.1×10-5 W/cm K2 and 0.25 at 940 K.