Colossal Seebeck coefficient in strongly correlated semiconductor FeSb ₂

For more than a decade strongly correlated semiconductors and Kondo insulators have been considered as potential thermoelectric materials. Such materials have large d - or f -character of the electronic band structure close to the Fermi level that theoretically leads to Seebeck coefficients ( S ) with large magnitudes. In this work it is shown for the first time that the strongly correlated semiconductor FeSb 2 exhibits a colossal Seebeck coefficient of ∼−45000 μVK −1 at 10 K. The thermoelectric power factor PF = S 2 ·ρ −1 , where ρ is the electrical resistivity, reaches a record high value of ∼2300 μWK −2 cm −1 at 12 K and is 65 times larger than that of the state-of-the-art Bi 2 Te 3 -based thermoelectric materials. However, due to a large lattice thermal conductivity the dimensionless thermoelectric figure of merit is only 0.005 at 12 K. Nonetheless, the potential of FeSb 2 as a future solid-state thermoelectric cooling device at cryogenic temperatures is underlined.