High temperature thermoelectric properties of p- and n-type β-FeSi2 with some dopants

Cr doped p-type and Co doped n-type β-FeSi2 alloys have been prepared using a powder metallurgy technique. Then the effects of Cu and Ge additions on their thermoelectric properties were investigated. Thermoelectric power α, electrical conductivity, σ, and thermal conductivity, κ were measured in a temperature range from 373 to 973 K. Their thermoelectric power is found to decrease with increasing an amount of both Cu and Ge in both type of β-FeSi2. In contrast, their electrical conductivity exhibit opposite tendency with respect to the amount of both dopants. Their thermal conductivity is more effectively reduced in the Ge addition to them than that in the Cu addition. The figure of merit, Z of binary β-FeSi2 is 0.19×10−4/K, and increases by the addition of Cr, Co, and Ge. The maximum figure of merit, Z of 1.3×10−4/K was obtained in Fe0.95Co0.05Si1.958Ge0.042 at 845 K.