Topological Insulator VxBi1.08-xSn0.02Sb0.9Te2S as a Promising n-type Thermoelectric Material

TL;DR

This study introduces V-doped Bi1.08Sn0.02Sb0.9Te2S as a novel topological insulator with enhanced thermoelectric performance, combining low thermal conductivity and high electrical conductivity due to surface states and phonon scattering.

Contribution

It reports a new bulk-insulating topological material with tunable band gap and high thermoelectric efficiency, replacing traditional Bi2Te3-based materials with a cost-effective, high-performance alternative.

Findings

Achieved a ZT of ~0.8 at 550 K in 2% V-doped sample

Demonstrated low lattice thermal conductivity due to secondary phase scattering

Showed high-mobility topological surface states enhance electrical conductivity

Abstract

As one of the most important n-type thermoelectric (TE) materials, Bi2Te3 has been studied for decades, with efforts to enhance the thermoelectric performance based on element doping, band engineering, etc. In this study, we report a novel bulk-insulating topological material system as a replacement for n-type Bi2Te3 materials: V doped Bi1.08Sn0.02Sb0.9Te2S (V:BSSTS) . The V:BSSTS is a bulk insulator with robust metallic topological surface states. Furthermore, the bulk band gap can be tuned by the doping level of V, which is verified by magnetotransport measurements. Large linear magnetoresistance is observed in all samples. Excellent thermoelectric performance is obtained in the V:BSSTS samples, e.g., the highest figure of merit ZT of ~ 0.8 is achieved in the 2% V doped sample (denoted as V0.02) at 550 K. The high thermoelectric performance of V:BSSTS can be attributed to two synergistic effects: (1) the low conductive secondary phases Sb2S3, and V2S3 are believed to be important scattering centers for phonons, leading to lower lattice thermal conductivity; and (2) the electrical conductivity is increased due to the high-mobility topological surface states at the boundaries. In addition, by replacing one third of costly tellurium with abundant, low-cost, and less-toxic sulfur element, the newly produced BSSTS material is inexpensive but still has comparable TE performance to the traditional Bi2Te3-based materials, which offers a cheaper plan for the electronics and thermoelectric industries. Our results demonstrate that topological materials with unique band structures can provide a new platform in the search for new high performance TE materials.