Broadening the optimum thermoelectric power generation range of p-type sintered Bi0.4Sb1.6Te3 by suppressing bipolar effect

Bi2Te3-based compounds are well-known commercial thermoelectric materials near room temperature. However, the strong intrinsic excitations above 400 K severely deteriorate the ZT values and limit the applications of thermoelectric power generation. Here, we choose divalent Pb as an acceptor impurity to improve the thermoelectric performance of p-type Bi0.4Sb1.6Te3 sintered materials at higher temperature. Tiny Pb doping not only obviously suppresses the bipolar effect by increasing the hole concentrations, but also decreases the lattice thermal conductivity via introducing phonon scattering centers, such as grain boundaries, dislocations, and dislocation strains. Consequently, a peak ZT of 1.2 at 375 K and a ZTave of 1.1 from 300 to 500 K are realized. A thermoelectric module comprised of our Bi0.4Sb1.597Pb0.003Te3 and commercial Bi2Te2.5Se0.5 is constructed and the evaluated energy conversion efficiency can reach 5.1 % under a temperature difference of 200 K. This study demonstrates that tiny Pb-doped Bi0.4Sb1.6Te3 is promising for low-grade heat recovery.