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Title: High thermoelectric performance in (Bi 0.25Sb 0.75) 2Te 3 due to band convergence and improved by carrier concentration control

Abstract

Bi 2Te 3 has been recognized as an important cooling material for thermoelectric applications. Yet its thermoelectric performance could still be improved. Here we propose a band engineering strategy by optimizing the converging valence bands of Bi 2Te 3 and Sb 2Te 3 in the (Bi 1-xSb x) 2Te 3 system when x = 0.75. Band convergence successfully explains the sharp increase in density-of-states effective mass yet relatively constant mobility and optical band gap measurement. This band convergence picture guides the carrier concentration tuning for optimum thermoelectric performance. To synthesize homogeneous textured and optimally doped (Bi 0.25Sb 0.75) 2Te 3, excess Te was chosen as the dopant. Uniform control of the optimized thermoelectric composition was achieved by zone-melting which utilizes separate solidus and liquidus compositions to obtain zT = 1.05 (at 300 K) without nanostructuring.

Authors:
ORCiD logo [1];  [2];  [2];  [3]; ORCiD logo [3];  [3]
  1. Northwestern Univ., Evanston, IL (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States); Samsung Advanced Institute of Technology, Samsung Electronics (South Korea)
  2. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  3. Northwestern Univ., Evanston, IL (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States)
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Solid-State Solar-Thermal Energy Conversion Center (S3TEC); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1470452
Grant/Contract Number:  
SC0001299; FG02-09ER46577
Resource Type:
Accepted Manuscript
Journal Name:
Materials Today
Additional Journal Information:
Journal Volume: 20; Journal Issue: 8; Related Information: S3TEC partners with Massachusetts Institute of Technology (lead); Boston College; Oak Ridge National Laboratory; Rensselaer Polytechnic Institute; Journal ID: ISSN 1369-7021
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; solar (photovoltaic); solar (thermal); solid state lighting; phonons; thermal conductivity; thermoelectric; defects; mechanical behavior; charge transport; spin dynamics; materials and chemistry by design; optics; synthesis (novel materials); synthesis (self-assembly); synthesis (scalable processing)

Citation Formats

Kim, Hyun-Sik, Heinz, Nicholas A., Gibbs, Zachary M., Tang, Yinglu, Kang, Stephen D., and Snyder, G. Jeffrey. High thermoelectric performance in (Bi0.25Sb0.75)2Te3 due to band convergence and improved by carrier concentration control. United States: N. p., 2017. Web. doi:10.1016/j.mattod.2017.02.007.
Kim, Hyun-Sik, Heinz, Nicholas A., Gibbs, Zachary M., Tang, Yinglu, Kang, Stephen D., & Snyder, G. Jeffrey. High thermoelectric performance in (Bi0.25Sb0.75)2Te3 due to band convergence and improved by carrier concentration control. United States. doi:10.1016/j.mattod.2017.02.007.
Kim, Hyun-Sik, Heinz, Nicholas A., Gibbs, Zachary M., Tang, Yinglu, Kang, Stephen D., and Snyder, G. Jeffrey. Wed . "High thermoelectric performance in (Bi0.25Sb0.75)2Te3 due to band convergence and improved by carrier concentration control". United States. doi:10.1016/j.mattod.2017.02.007. https://www.osti.gov/servlets/purl/1470452.
@article{osti_1470452,
title = {High thermoelectric performance in (Bi0.25Sb0.75)2Te3 due to band convergence and improved by carrier concentration control},
author = {Kim, Hyun-Sik and Heinz, Nicholas A. and Gibbs, Zachary M. and Tang, Yinglu and Kang, Stephen D. and Snyder, G. Jeffrey},
abstractNote = {Bi2Te3 has been recognized as an important cooling material for thermoelectric applications. Yet its thermoelectric performance could still be improved. Here we propose a band engineering strategy by optimizing the converging valence bands of Bi2Te3 and Sb2Te3 in the (Bi1-xSbx)2Te3 system when x = 0.75. Band convergence successfully explains the sharp increase in density-of-states effective mass yet relatively constant mobility and optical band gap measurement. This band convergence picture guides the carrier concentration tuning for optimum thermoelectric performance. To synthesize homogeneous textured and optimally doped (Bi0.25Sb0.75)2Te3, excess Te was chosen as the dopant. Uniform control of the optimized thermoelectric composition was achieved by zone-melting which utilizes separate solidus and liquidus compositions to obtain zT = 1.05 (at 300 K) without nanostructuring.},
doi = {10.1016/j.mattod.2017.02.007},
journal = {Materials Today},
number = 8,
volume = 20,
place = {United States},
year = {2017},
month = {6}
}

Journal Article:
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Cited by: 11 works
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Figures / Tables:

FIGURE 1 FIGURE 1: Band related properties as a function of composition (x) for (Bi1–xSbx)2Te3 at 300 K. (a) Density-of-states effective mass (red circle with error bars in dotted lines) showing an abrupt peak (grey line as guide to the eye) while the mobility prefactor (b) shows no such change at xmore » = 0.75. (c) Brillouin zone of Bi2Te3 (x = 0) showing hole pockets for the first valence band (in purple) and for the second valence band (in green). (d) Semi-empirical band structure (300 K) with the first valence band (purple line), second valence band (green line), and the lowest conduction band (dark grey line). For simplicity, the energy of the first valence band (purple) of Bi2Te3 (x = 0) is set to 0.0 eV. ΔEVB1– VB2 denotes energy difference between the first and second valence bands. The energy gap between the lowest conduction band (dark grey) and the highest valence band (purple for 0 ≤ x ≤ 0.75 and green for 0.75 ≤ x ≤ 1) is the band gap Eg(x).« less

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.