Enhanced thermoelectric properties of bismuth and zinc co-doped SnTe by band engineering and all-scale structure defects

Abstract

SnTe is considered as the appropriate substituent candidate of traditional PbTe due to the environmental-friendly nature. Herein, a series of Sn1–3xBi2xZnxTe (x = 0, 0.01, 0.02, 0.03) and Sn1–3xBi2xZnxTe-5%Cu2Te samples are fabricated, and their thermoelectric performances are studied. We first demonstrate that the solubility limit of the Zn in SnTe is less than 1% under the conventional melting process and the excess ZnTe precipitated in the matrix. Secondly, co-doping of Bi and Zn synergistically enhances electrical properties significantly over a wide temperature range due to Bi-doping-driven band convergence and Zn-doping-driven resonant level supported by computational calculations of DFT. Moreover, Zn-doping-induced precipitates with nano- to micro-meter size, Bi/Zn dual-point defect and Cu2Te-alloying-induced interstitial atoms can simultaneously block phonon transport in wide frequency range, resulting in an ultralow lattice thermal conductivity of ~0.51 W−1m−1K−1 at 873 K. Consequently, the synergistic regulation of electrical and thermal properties yields a peak ZT of ~ 1.3 at 873 K for Sn0.94Bi0.04Zn0.02Te- 5%Cu2Te samples. This high performance material is earth-abundant, low cost and nontoxic, which is more propitious to thermoelectric generator applications.