@article{21beb06af41e4c1b8643c4dbe959a216,
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}",
note = "Funding Information: 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. Publisher Copyright: {\textcopyright} 2021 Elsevier Inc.",
year = "2021",
month = may,
day = "19",
doi = "10.1016/j.joule.2021.03.009",
language = "English (US)",
volume = "5",
pages = "1168--1182",
journal = "Joule",
issn = "2542-4351",
publisher = "Cell Press",
number = "5",
}