Constructing van der Waals gaps in cubic-structured SnTe-based thermoelectric materials

Author(s): Xiao Xu ¹ ^, ² ^, ³ ^, ⁴ , Juan Cui ¹ ^, ² ^, ³ ^, ⁴ , Yong Yu ¹ ^, ² ^, ³ ^, ⁴ , Bin Zhu ¹ ^, ² ^, ³ ^, ⁴ , Yi Huang ¹ ^, ² ^, ³ ^, ⁴ , Lin Xie ¹ ^, ² ^, ³ ^, ⁴ , Di Wu ⁵ ^, ⁶ ^, ⁷ ^, ⁴ , Jiaqing He ¹ ^, ² ^, ³ ^, ⁴

Publication date (Electronic): 2020

Journal: Energy & Environmental Science

Publisher: Royal Society of Chemistry (RSC)

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Abstract

A new strategy of constructing van der Waals gaps in cubic-structured Sb ₂Te ₃(SnTe) _n is presented to enhance the thermoelectric properties.

Abstract

The practical application of eco-friendly tin telluride (SnTe) at intermediate temperatures has been long restricted by its lower average ZT than that of state-of-art PbTe. Here, a maximal figure of merit ZT _max ∼ 1.4 at 773 K and an ultrahigh ZT _ave ∼ 0.83 (between 323 and 773 K) are realized in SnTe by alloying with Sb ₂Te ₃ and follow-up rhenium doping. Microstructural characterizations reveal that Sb ₂Te ₃ alloying produces van der Waals gap-like structure throughout the SnTe matrix, leading to a significant reduction of lattice thermal conductivity; rhenium doping can tune the carrier concentration precisely at high temperatures, thus further improving the power factor. The construction of gap-like structure in our Sb ₂Te ₃(SnTe) _n samples and its remarkable effect on thermoelectric transports can shed light for future studies of SnTe and analogous thermoelectric systems.

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Most cited references 39

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Convergence of electronic bands for high performance bulk thermoelectrics.

Yanzhong Pei, Xiaoya Shi, Aaron D LaLonde … (2011)

Thermoelectric generators, which directly convert heat into electricity, have long been relegated to use in space-based or other niche applications, but are now being actively considered for a variety of practical waste heat recovery systems-such as the conversion of car exhaust heat into electricity. Although these devices can be very reliable and compact, the thermoelectric materials themselves are relatively inefficient: to facilitate widespread application, it will be desirable to identify or develop materials that have an intensive thermoelectric materials figure of merit, zT, above 1.5 (ref. 1). Many different concepts have been used in the search for new materials with high thermoelectric efficiency, such as the use of nanostructuring to reduce phonon thermal conductivity, which has led to the investigation of a variety of complex material systems. In this vein, it is well known that a high valley degeneracy (typically ≤6 for known thermoelectrics) in the electronic bands is conducive to high zT, and this in turn has stimulated attempts to engineer such degeneracy by adopting low-dimensional nanostructures. Here we demonstrate that it is possible to direct the convergence of many valleys in a bulk material by tuning the doping and composition. By this route, we achieve a convergence of at least 12 valleys in doped PbTe(1-x)Se(x) alloys, leading to an extraordinary zT value of 1.8 at about 850 kelvin. Band engineering to converge the valence (or conduction) bands to achieve high valley degeneracy should be a general strategy in the search for and improvement of bulk thermoelectric materials, because it simultaneously leads to a high Seebeck coefficient and high electrical conductivity. ©2011 Macmillan Publishers Limited. All rights reserved

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Model for Lattice Thermal Conductivity at Low Temperatures

Joseph Callaway (1959)

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High-performance bulk thermoelectrics with all-scale hierarchical architectures.

Kanishka Biswas, Jiaqing He, Ivan Blum … (2012)

With about two-thirds of all used energy being lost as waste heat, there is a compelling need for high-performance thermoelectric materials that can directly and reversibly convert heat to electrical energy. However, the practical realization of thermoelectric materials is limited by their hitherto low figure of merit, ZT, which governs the Carnot efficiency according to the second law of thermodynamics. The recent successful strategy of nanostructuring to reduce thermal conductivity has achieved record-high ZT values in the range 1.5-1.8 at 750-900 kelvin, but still falls short of the generally desired threshold value of 2. Nanostructures in bulk thermoelectrics allow effective phonon scattering of a significant portion of the phonon spectrum, but phonons with long mean free paths remain largely unaffected. Here we show that heat-carrying phonons with long mean free paths can be scattered by controlling and fine-tuning the mesoscale architecture of nanostructured thermoelectric materials. Thus, by considering sources of scattering on all relevant length scales in a hierarchical fashion--from atomic-scale lattice disorder and nanoscale endotaxial precipitates to mesoscale grain boundaries--we achieve the maximum reduction in lattice thermal conductivity and a large enhancement in the thermoelectric performance of PbTe. By taking such a panoscopic approach to the scattering of heat-carrying phonons across integrated length scales, we go beyond nanostructuring and demonstrate a ZT value of ∼2.2 at 915 kelvin in p-type PbTe endotaxially nanostructured with SrTe at a concentration of 4 mole per cent and mesostructured with powder processing and spark plasma sintering. This increase in ZT beyond the threshold of 2 highlights the role of, and need for, multiscale hierarchical architecture in controlling phonon scattering in bulk thermoelectrics, and offers a realistic prospect of the recovery of a significant portion of waste heat.

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Author and article information

Contributors

Di Wu: (View ORCID Profile)

Jiaqing He: (View ORCID Profile)

Journal

Journal ID (publisher-id): EESNBY

Title: Energy & Environmental Science

Abbreviated Title: Energy Environ. Sci.

Publisher: Royal Society of Chemistry (RSC)

ISSN (Print): 1754-5692

ISSN (Electronic): 1754-5706

Publication date Created: December 16 2020

Publication date (Electronic): 2020

Volume: 13

Issue: 12

Pages: 5135-5142

Affiliations

[1 ]Department of Physics

[2 ]Southern University of Science and Technology

[3 ]Shenzhen

[4 ]China

[5 ]School of Materials Science and Engineering

[6 ]Shaanxi Normal University

[7 ]Xi’an

Article

DOI: 10.1039/D0EE02638G

SO-VID: ec727617-9d72-4526-9a66-c9d9065b0a67

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