Simultaneous optimization of Seebeck, electrical and thermal conductivity in free-solidified Bi_0.4Sb_1.6Te₃ alloy via liquid-state manipulation

(BiSb)₂Te₃-based alloy is one of the best p-type thermoelectric (TE) materials near room temperature. However, it is challenging to improve its ZT value due to the interrelated Seebeck coefficient (S), electrical conductivity (#sigma#), and thermal conductivity (#kappa#). In this study, the synergistic optimization of S, #sigma#, and #kappa# has been easily achieved in Bi_0.4Sb_1.6Te₃ alloy by liquid-state manipulation (LSM). Specifically, more Te-rich eutectic strips are observed in the LSM sample, which would increase carrier density (p) and thus improve #sigma#. Meanwhile, via LSM, the raised effective mass m^* could compensate the effect of increased p on S and thus an enhanced S is obtained. Furthermore, the larger amount of nanoparticles, higher density of lattice distortions, and dislocations in the LSM sample would contribute to scattering phonons and a lower κ is attained. As a result, the highest ZT of 0.7 at 352 K is attained which is 40% higher than that of traditional melted Bi_0.4Sb_1.6Te₃ alloy.