Charge-carrier-mediated lattice softening contributes to high zT in thermoelectric semiconductors

Tyler J. Slade; Shashwat Anand; Max Wood; James P. Male; Kazuki Imasato; Dean Cheikh; Muath M. Al Malki; Matthias T. Agne; Kent J. Griffith; Sabah K. Bux; Chris Wolverton; Mercouri G. Kanatzidis; G. Jeffrey Snyder

doi:10.1016/j.joule.2021.03.009

Charge-carrier-mediated lattice softening contributes to high zT in thermoelectric semiconductors

Tyler J. Slade, Shashwat Anand, Max Wood, James P. Male, Kazuki Imasato, Dean Cheikh, Muath M. Al Malki, Matthias T. Agne, Kent J. Griffith, Sabah K. Bux, Chris Wolverton, Mercouri G. Kanatzidis, G. Jeffrey Snyder^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

43 Scopus citations

Abstract

High phonon velocities, i.e., as measured by the speed of sound (v_s) lead to high lattice thermal conductivity (κ_lat), which is detrimental to thermoelectric performance. Conventional wisdom associates v_s exclusively with structural features such as average atomic mass but not the number of conducting electrons. Here, we demonstrate v_s reduction from electronic doping in eight well-known thermoelectric semiconductors and establish carrier density n_H as the main cause for the observed lattice softening by ruling out alternative factors such as changes in density, average atomic mass, and defect formation. In p-type SnTe and n-type La_3–xTe₄, we find respective decreases of 16% and ∼20% in v_s when raising the n_H from ∼10¹⁹ to 10²¹ cm^–3, which is sufficient to decrease κ_lat by nearly 50%. Such giant softening effects can account for 25% of the optimized thermoelectric figure of merit (zT_max) in high-performing materials (zT_max > 1) by suppressing total thermal conductivity.

Original language	English (US)
Pages (from-to)	1168-1182
Number of pages	15
Journal	Joule
Volume	5
Issue number	5
DOIs	https://doi.org/10.1016/j.joule.2021.03.009
State	Published - May 19 2021

Funding

We thank Dr. Riley Hanus for inspiring discussions on lattice-softening mechanisms for thermal conductivity reduction. This work was supported in part by the U.S Department of Energy , Office of Science, and Office of Basic Energy Sciences under award number DE-SC0014520 (T.J.S. and M.G.K., sample synthesis and characterization; C.W., DFT calculations). S. A. and G. J. S. acknowledge the support from National Science Foundation ( DMREF-1729487 ). M.W., D.C., and S.K.B. are supported by the National Aeronautics and Space Administration (NASA) Science Missions Directorate under the Radioisotope Power Systems Program. J.M. acknowledges the support of award 70NANB19H005 from the U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design ( CHiMaD ) and his work was supported by a NASA Space Technology Graduate Research Opportunities Award. K.I. and M.T.A. acknowledge the support from the U.S. Department of Energy , Office of Energy Efficiency and Renewable Energy (EERE) program “Accelerated Discovery of Compositionally Complex Alloys for Direct Thermal Energy Conversion” (DOE award DE-AC02-76SF00515 ). Muath M. Al Malki acknowledges the fellowship support from KFUPM (King Fahd University for Petroleum and Minerals), Saudi Arabia.

Keywords

batteries
electron-phonon coupling
lattice dynamics
lattice softerning
phonon renormalization
thermal conductivity
thermoelectrics

ASJC Scopus subject areas

General Energy

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10.1016/j.joule.2021.03.009

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title = "Charge-carrier-mediated lattice softening contributes to high zT in thermoelectric semiconductors",

abstract = "High phonon velocities, i.e., as measured by the speed of sound (vs) lead to high lattice thermal conductivity (κlat), which is detrimental to thermoelectric performance. Conventional wisdom associates vs exclusively with structural features such as average atomic mass but not the number of conducting electrons. Here, we demonstrate vs reduction from electronic doping in eight well-known thermoelectric semiconductors and establish carrier density nH as the main cause for the observed lattice softening by ruling out alternative factors such as changes in density, average atomic mass, and defect formation. In p-type SnTe and n-type La3–xTe4, we find respective decreases of 16% and ∼20% in vs when raising the nH from ∼1019 to 1021 cm–3, which is sufficient to decrease κlat by nearly 50%. Such giant softening effects can account for 25% of the optimized thermoelectric figure of merit (zTmax) in high-performing materials (zTmax > 1) by suppressing total thermal conductivity.",

keywords = "batteries, electron-phonon coupling, lattice dynamics, lattice softerning, phonon renormalization, thermal conductivity, thermoelectrics",

author = "Slade, {Tyler J.} and Shashwat Anand and Max Wood and Male, {James P.} and Kazuki Imasato and Dean Cheikh and {Al Malki}, {Muath M.} and Agne, {Matthias T.} and Griffith, {Kent J.} and Bux, {Sabah K.} and Chris Wolverton and Kanatzidis, {Mercouri G.} and Snyder, {G. Jeffrey}",

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doi = "10.1016/j.joule.2021.03.009",

language = "English (US)",

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AU - Slade, Tyler J.

AU - Anand, Shashwat

AU - Wood, Max

AU - Male, James P.

AU - Imasato, Kazuki

AU - Cheikh, Dean

AU - Al Malki, Muath M.

AU - Agne, Matthias T.

AU - Griffith, Kent J.

AU - Bux, Sabah K.

AU - Wolverton, Chris

AU - Kanatzidis, Mercouri G.

AU - Snyder, G. Jeffrey

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N2 - High phonon velocities, i.e., as measured by the speed of sound (vs) lead to high lattice thermal conductivity (κlat), which is detrimental to thermoelectric performance. Conventional wisdom associates vs exclusively with structural features such as average atomic mass but not the number of conducting electrons. Here, we demonstrate vs reduction from electronic doping in eight well-known thermoelectric semiconductors and establish carrier density nH as the main cause for the observed lattice softening by ruling out alternative factors such as changes in density, average atomic mass, and defect formation. In p-type SnTe and n-type La3–xTe4, we find respective decreases of 16% and ∼20% in vs when raising the nH from ∼1019 to 1021 cm–3, which is sufficient to decrease κlat by nearly 50%. Such giant softening effects can account for 25% of the optimized thermoelectric figure of merit (zTmax) in high-performing materials (zTmax > 1) by suppressing total thermal conductivity.

AB - High phonon velocities, i.e., as measured by the speed of sound (vs) lead to high lattice thermal conductivity (κlat), which is detrimental to thermoelectric performance. Conventional wisdom associates vs exclusively with structural features such as average atomic mass but not the number of conducting electrons. Here, we demonstrate vs reduction from electronic doping in eight well-known thermoelectric semiconductors and establish carrier density nH as the main cause for the observed lattice softening by ruling out alternative factors such as changes in density, average atomic mass, and defect formation. In p-type SnTe and n-type La3–xTe4, we find respective decreases of 16% and ∼20% in vs when raising the nH from ∼1019 to 1021 cm–3, which is sufficient to decrease κlat by nearly 50%. Such giant softening effects can account for 25% of the optimized thermoelectric figure of merit (zTmax) in high-performing materials (zTmax > 1) by suppressing total thermal conductivity.

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KW - electron-phonon coupling

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KW - phonon renormalization

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KW - thermoelectrics

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Charge-carrier-mediated lattice softening contributes to high zT in thermoelectric semiconductors

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