Enhanced thermoelectric performance of Bi2Te2.7Se0.3 by constructing multiple interfaces through the introduction of heterojunction compounds

Abstract

Enhancing phonon scattering has emerged as an effective strategy for suppressing lattice thermal conductivity (κ_L), thereby improving the performance of bulk thermoelectric materials. Compared with other strategies, the primary purpose of introducing more grain boundaries is to enhance the scattering of mid to low-frequency phonons, consequently reducing the κ_L at the near-room temperature, which proves advantageous for enhancing the thermoelectric properties of Bismuth telluride-based materials. In this study, MnS/MoS₂ as a heterojunction compound was incorporated into a Bi₂Te_2.7Se_0.3 matrix, resulting in the formation of a unique (Bi₂Te_2.7Se_0.3 → MnS → MoS₂) three grain boundary interface structure, which significantly enhanced phonon scattering. Additionally, the MnSe secondary phase was observed and confirmed through both X-ray diffraction (XRD) and transmission electron microscopy (TEM). The introduction of 0.3% MnS/MoS₂ leads to a reduction in the κ_L from 0.58 W m⁻¹ K⁻¹ to 0.41 W m⁻¹ K⁻¹ at 300 K. Simultaneously, the synergistic optimization of electrical properties results in a PF of 33 µW cm⁻¹ K⁻² at 300 K. Finally, a high ZT value ∼1.17 (375 K) and an average ZT_ave ∼ 1.08 (300–500 K) were achieved for Bi₂Te_2.7Se_0.3–0.3% MnS/MoS₂, which was enhanced 54% and 57% compared with those of the Bi₂Te_2.7Se_0.3 alloy, respectively.