Re-optimising the thermoelectric properties of BiTeSe by CuO doping: From zone-melting ingots to powder metallurgy bulks with a large size.

The Bi 2 Te 3 -based thermoelectric crystal ingots produced by the zone-melting (ZM) are the most widely used commercially at present. However, the poor mechanical properties caused by the ZM are unfavorable to the production of miniature devices. The mechanical properties can be improved by the powder metallurgy (PM), but the PM results in performance degradation of n -type Bi 2 Te 3 -based alloys, which could be attributed to the disappearance of intrinsic anisotropy and the increased carrier concentration originated from the "donor-like" effect of grain boundary. In this paper, the Bi 2 Te 2.7 Se 0.3 + 4 wt % Te (BTST) powder was from the ground ZM ingots, and the influence of CuO doping on the thermoelectric properties of hot-pressed BTST polycrystalline bulks with a large size was investigated. It can be found that the thermoelectric properties of BTST are improved remarkably by CuO doping due to the increased Seebeck coefficient and suppressed thermal conductivity, which is caused by the synthetic effects of optimised carrier concentration, increased effective mass, and enhanced phonon scattering by the Cu 2 Te/Bi 2 Te 2.7 Se 0.3 hetero-interfaces. Finally, the dimensionless thermoelectric figure of merit (ZT) of the sample (CuO) 0.1 (Bi 2 Te 2.7 Se 0.3 + 4 wt % Te) reaches 1.32 at 408 K, which is about 65 % higher than that of the pristine BTST, and its average ZT ave value reaches 1.27 in the temperature range of 300–473 K. The large size bulks produced by this method are not only commercialized directly, but also avoid the problem of poor mechanical properties. • Effects of CuO doping on the thermoelectric properties of Bi 2 Te 2.7 Se 0.3 + 4 wt% Te. • Simultaneous optimization of power factors (S2σ) and thermal conductivity (κ). • High peak ZT max of 1.32 at 408 K, and high average ZT ave of 1.27 from 300 K to 473 K. • Large size of 30 mm*30 mm*70 mm. [ABSTRACT FROM AUTHOR]