Thermoelectric properties of chemically substituted full-Heusler Fe2TiSn1-xSbx (x = 0, 0.1, and 0.2) compounds

peer reviewedAccording to theoretical predictions [Phys. Rev. Lett. 114, 136601 (2015)], Sb substitution in Fe2TiSn full-Heusler compounds is thought to enhance the n-type thermoelectric power factors. We prepare Fe2TiSn samples with 0%, 10%, and 20% Sb substitution on the Sn site and study the effects of the heat treatment protocol and of Sb substitution by structural characterization, electrical, thermoelectrical, and thermal transport measurements from room temperature down to 10 K, and by comparison with ab initio calculations. For the undoped Fe2TiSn phase, we find a bad metallic gapless transport behavior in the as-cast sample and a small gap semiconducting behavior for the annealed samples. These observations, together with the p-type character emerging from the Hall effect and Seebeck effect, are explained by ab initio calculations, provided that antisite disorder and vacancy defects are included. In these undoped Fe2TiSn samples, we find that increasing thermal annealing temperature up to 800 °C slightly decreases the carrier concentration, enhances the Seebeck coefficient in the low-temperature regime (below 100–200 K), induces magnetic ordering at low temperature (