Effective dopants in p-type elementary Te thermoelectrics†
Elementary Te is predicted to be a high-performance thermoelectric material through theoretical calculation, and the experimental results have confirmed this prediction through optimizing carrier concentrations. In this work, we investigate the thermoelectric transport properties in undoped Te at 300–673 K, revealing a low thermal conductivity ∼1.8 W m−1 K−1 at room temperature and a ZT ∼ 0.2 at 653 K. To further improve the thermoelectric performance in the Te system, we choose Sn, Pb, Bi, and Sb as dopants in Te. We find Bi and Sb can effectively enhance the electrical conductivity by two orders, from ∼2 S cm−1 in undoped Te to ∼300 S cm−1 and ∼550 S cm−1 at 300 K in Bi-doped and Sb-doped samples respectively. Meanwhile, these dopants can simultaneously significantly suppress the lattice thermal conductivity, decreasing from 1.22 W m−1 K−1 in undoped Te to 0.68 W m−1 K−1 and 0.73 W m−1 K−1 at 673 K in Bi-doped and Sb-doped samples, respectively. Maximum ZT values of ∼0.8 in Te0.9925Bi0.0075 and ∼1.1 in Te0.985Sb0.015 at 673 K can be achieved. The results indicate that Sb is an effective dopant in the Te system.