Enhanced Thermoelectric Performance of Te-Doped Bi2Se3−xTex Bulks by Self-Propagating High-Temperature Synthesis

Rui Liu,Zhifang Zhou,Guangkun Ren,Yuanhua Lin,Xing Tan,Cewen Nan,Chan Liu,Yaochun Liu

doi:10.3390/cryst7090257

Abstract

Polycrystalline Bi2Se3−xTex (x = 0~1.5) samples were prepared by self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering (SPS) and their thermoelectric properties were investigated. The SHS-SPS process can shorten the time with few energy consumptions, and obtain almost pure Bi2Se3-based phases. Consequently, the Se vacancies and anti-site defects contribute to the converged carrier concentration of ~2 × 1019 cm−3 while the increased carrier effective mass enhances the Seebeck coefficient to more than −158 μV K−1 over the entire temperature range. The lattice thermal conductivity is suppressed from 1.07 Wm−1 K−1 for the pristine specimen to ~0.6 Wm−1 K−1 for Te-substitution samples at 300 K because of point defects caused by the difference of mass and size between Te and Se atoms. Coupled with the enhanced power factor and reduced lattice thermal conductivity, a high ZT of 0.67 can be obtained at 473 K for the Bi2Se1.5Te1.5 sample. Our results reveal that Te-substitution based on the SHS-SPS method is highly-efficient and can improve the thermoelectric properties of Bi2Se3-based materials largely.

Highlights

With increasing attention on the environmental protection and renewable resources, thermoelectric (TE) instruments, which can directly convert heat into electricity, are considered as a potential solution for harness waste heat [1,2,3]
Considerable numbers of efforts have been devoted to improving the energy conversion efficiency and the stability of the TE materials [4]
The electrical properties including electrical conductivity and Seebeck coefficient were measured from room temperature to 593 K by ZEM-3 (ULVAC, Kanagawa, Japan)

Summary

Introduction

With increasing attention on the environmental protection and renewable resources, thermoelectric (TE) instruments, which can directly convert heat into electricity, are considered as a potential solution for harness waste heat [1,2,3]. To maximize the ZT value of a kind of material, a large Seebeck coefficient, electrical conductivity and low thermal conductivity are needed. These parameters have a strong coupling with each other, which makes it a challenging task to enhance ZT significantly. Self-propagating high-temperature synthesis (SHS) has been proved to be an efficient method to prepare the TE materials alternatively. We successfully synthesized Bi2Se3−xTex (x = 0, 0.3, 0.6, 0.9, 1.2, 1.5) via the SHS method followed by spark plasma sintering (SPS) and studied the thermoelectric properties from 300 K to 593 K. SHS process will have more hopeful prospects in commercial applications

Experimental Procedures

Results and Discussion

Se3the

Conclusions