Abstract
Bismuth-antimony () alloys have the highest thermoelectric figure of merit of all -type thermoelectric materials below 200 K. They are the only Te-free thermoelectric alternatives to the tetradymite materials for applications at and below room temperature. Single-crystal alloys show the maximum figure of merit at 200 K along the trigonal axis crystallographic direction, but the cost associated with single-crystal growth and the tendency of single crystals to cleave preclude their use. Mechanically robust polycrystalline / nanocomposites are shown here to be able to reach competitive values. Two compositions are investigated, and . Thermal and electrical transport properties confirm significant reduction of lattice thermal conductivity in the nanocomposite samples, but the concurrent loss of electrical conductivity leads to an unfavorable net effect on . In contrast, a large increase in thermopower is observed in the / nanocomposite system, which is attributed to a better optimized doping level. Accordingly, the of a / nanocomposite sample is shown to reach at 240 K, which rivals that of single crystals. Near room temperature, the of the nanocomposite sample is improved by over that of the single-crystalline sample. Galvano- and thermomagnetic analysis suggests a strong effect of carrier concentration on the of nanocomposite samples.
- Received 17 May 2018
DOI:https://doi.org/10.1103/PhysRevMaterials.2.115401
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