Sb₂Te₃ based alloy with high thermoelectric and mechanical performance for low-temperature energy harvesting

Introducing nanostructures is an effective method to improve the performance of thermoelectric materials. However, the strength of the nano Sb₂Te₃ based materials deteriorates significantly between 573 and 673 K, which severely limits its application in energy harvesting. The motivation of this work is to develop p-type Sb₂Te₃-based alloys with high mechanical property and high figure-of-merit ZT over a wide temperature range. Fine grains and nano-twins are formed simultaneously by reducing Te content and high-energy ball milling, resulting in a lower lattice thermal conductivity and better mechanical properties. Copper doping is applied to further optimize the carrier and phonon transport behavior while maintaining excellent mechanical properties. In consequence, the ZT value of Sb_1.82In_0.15Cu_0.03Te_2.98 sample is enhanced up to 1.06 at 623 K and a fairly high ZT_ave of 0.76 from 300 K to 673 K is achieved. To achieve a high conversion efficiency within a wider temperature range, a p-type segment leg composed of the present material and the low-temperature Bi_0.4Sb_1.6Te_3.01 is fabricated via one-step sintering, and it shows an efficiency as high as 9.2 % under the temperature difference of 380 K.