Thermoelectric properties of β-Fe1-xCoxSi2 semiconductors

The thermoelectric properties of Co-substituted beta -FeSi2 (Fe1-xCoxSi2, 0.00 less than or equal to x less than or equal to 0.10) have been characterized by Hall effect measurements at 300 K and by measurements of electrical resistivity (rho), Seebeck coefficient (S), and thermal conductivity (K) 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 less than or equal to x less than or equal to 0.05, kappa decreases with increasing temperature, reaches a minimum, and increases. At x = 0.10, the K increases monotonically with increasing temperature. From the composition and temperature dependences of K, it was found that the thermal conductivity of the lattice component K-ph is dominant in Fe1-xCoxSi2 semiconductors. At low temperatures, K-ph can be explained by the presence of small polarons. At x = 0.05, the power factor (P = S-2/rho) as well as the dimensionless figure of merit (ZT) shows a maximum value of 1.1 x 10(-5) W/cm K-2 and 0.25 at 940 K.