Thermoelectric generators have the unique ability to convert waste heat into useable electrical power. However, traditional longitudinal thermoelectric generators (TEGs) that incorporate both p-type (hole-conducting) and n-type (electron-conducting) materials into a single module face major engineering problems. Transverse thermoelectric generators (TTEGs) use materials with axis-dependent conduction polarity to circumvent these challenges. In these materials, p-type and n-type functionalities are integrated along orthogonal directions within a single crystal, decoupling the directions of heat and charge flow in the device and eliminating the insertion losses that stem from electrical series contacts in TEGs. Re4Si7 is an excellent candidate for use in a TTEG because of its axis-dependent conduction polarity and its outstanding thermoelectric properties. In this work, large single crystals of Re4Si7 were used to fabricate transverse thermoelectric generators with two different geometries. The power output and efficiencies of both devices were fully characterized and demonstrate the advantages that TTEGs have over TEGs. While Re4Si7 demonstrates outstanding thermoelectric properties, Re is a rare and costly element. As a result, related phases WSi2 as well as Mo- and W-alloyed Re4Si7 were synthesized, characterized, and evaluated for similar applications.

Materials with axis-dependent conduction polarity make transverse thermoelectric generators a reality

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