Title: Thermal conductivity in Bi_0.5Sb_1.5Te_3+x and the role of dense dislocation arrays at grain boundaries

Abstract

Several prominent mechanisms for reduction in thermal conductivity have been shown in recent years to improve the figure of merit for thermoelectric materials. Such a mechanism is a hierarchical all-length-scale architecturing that recognizes the role of all microstructure elements, from atomic to nano to microscales, in reducing (lattice) thermal conductivity. In this context, there have been recent claims of remarkably low (lattice) thermal conductivity in Bi0.5Sb1.5Te3 that are attributed to seemingly ordinary grain boundary dislocation networks. These high densities of dislocation networks in Bi0.5Sb1.5Te3 were generated via unconventional materials processing with excess Te (which formed liquid phase, thereby facilitating sintering), followed by spark plasma sintering under pressure to squeeze out the liquid. We reproduced a practically identical microstructure, following practically identical processing strategies, but with noticeably different (higher) thermal conductivity than that claimed before. We show that the resultant microstructure is anisotropic, with notable difference of thermal and charge transport properties across and along two orthonormal directions, analogous to anisotropic crystals. Thus, we believe that grain boundary dislocation networks are not the primary cause of enhanced ZT through reduction in thermal conductivity. Instead, we can reproduce the purported high ZT through a favorable but impractical and incorrect combination of thermalmore » conductivity measured along the pressing direction of anisotropy while charge transport measured in the direction perpendicular to the anisotropic direction. We believe that our work underscores the need for consistency in charge and thermal transport measurements for unified and verifiable measurements of thermoelectric (and related) properties and phenomena.« less

Authors:

Deng, Rigui  ^[1];

• Search DOE PAGES for author "Deng, Rigui"
• Search DOE PAGES for ORCID "0000-0002-7025-6912"

Su, Xianli  ^[2];

• Search DOE PAGES for author "Su, Xianli"
• Search DOE PAGES for ORCID "0000-0003-4428-6461"

Zheng, Zheng ^[1]; Liu, Wei ^[1]; Yan, Yonggao ^[1]; Zhang, Qingjie ^[1]; Dravid, Vinayak P.  ^[3];

• Search DOE PAGES for author "Dravid, Vinayak P."
• Search DOE PAGES for ORCID "0000-0002-6007-3063"

Uher, Ctirad  ^[4];

• Search DOE PAGES for author "Uher, Ctirad"
• Search DOE PAGES for ORCID "0000-0002-3270-1464"

Kanatzidis, Mercouri G.  ^[3];

• Search DOE PAGES for author "Kanatzidis, Mercouri G."
• Search DOE PAGES for ORCID "0000-0003-2037-4168"

Tang, Xinfeng ^[1]

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+ Show Author Affiliations

1. Wuhan University of Technology (China)
2. Wuhan University of Technology (China); Northwestern Univ., Evanston, IL (United States)
3. Northwestern Univ., Evanston, IL (United States)
4. Univ. of Michigan, Ann Arbor, MI (United States)

Publication Date:

Fri Jun 01 00:00:00 EDT 2018

Research Org.:

Northwestern Univ., Evanston, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1499916

Alternate Identifier(s):

OSTI ID: 1775291

Grant/Contract Number:  

SC0014520

Resource Type:

Accepted Manuscript

Journal Name:

Science Advances

Additional Journal Information:

Journal Volume: 4; Journal Issue: 6; Journal ID: ISSN 2375-2548

Publisher:

AAAS

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE