Thermoelectric performance and the role of anti-site disorder in the 24-electron Heusler TiFe2Sn

Abstract

Heusler compounds XY2Z with 24 valence electrons per formula unit are potential thermoelectric materials, given their thermal and chemical stability and their relatively earth-abundant constituent elements. We present results on the 24-electron compound TiFe2Sn here. First principles calculations on this compound suggest semiconducting behavior. A relatively flat conduction band that could be associated with a high Seebeck coefficient upon electron doping is found. A series of compounds have been prepared and characterized using a combination of synchrotron x-ray and neutron diffraction studies to understand the effects of site order/disorder phenomena and n-type doping. Samples fabricated by a three step processing approach were subjected to high temperature Seebeck and electrical resistivity measurements. Ti:Fe anti-site disorder is present in the stoichiometric compound and these defects are reduced when starting Ti–rich compositions are employed. Additionally, we investigate control of the Seebeck coefficient through the introduction of carriers through the substitution of Sb on the Sn site in these intrinsically p-type materials.