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Title: High Seebeck Coefficient and Unusually Low Thermal Conductivity Near Ambient Temperatures in Layered Compound Yb 2–xEu xCdSb 2

Abstract

Zintl phases are promising thermoelectric materials because they are composed of both ionic and covalent bonding, which can be independently tuned. An efficient thermoelectric material would have regions of the structure composed of a high-mobility compound semiconductor that provides the “electron–crystal” electronic structure, interwoven (on the atomic scale) with a phonon transport inhibiting structure to act as the “phonon–glass”. The phonon–glass region would benefit from disorder and therefore would be ideal to house dopants without disrupting the electron–crystal region. The solid solution of the Zintl phase, Yb 2–xEu xCdSb 2, presents such an optimal structure, and here we characterize its thermoelectric properties above room temperature. Thermoelectric property measurements from 348 to 523 K show high Seebeck values (maximum of ∼269 μV/K at 523 K) with exceptionally low thermal conductivity (minimum ∼0.26 W/m K at 473 K) measured via laser flash analysis. Speed of sound data provide additional support for the low thermal conductivity. Density functional theory (DFT) was employed to determine the electronic structure and transport properties of Yb 2CdSb 2 and YbEuCdSb 2. Lanthanide compounds display an f-band well below (∼2 eV) the gap. This energy separation implies that f-orbitals are a silent player in thermoelectric properties; however, wemore » find that some hybridization extends to the bottom of the gap and somewhat renormalizes hole carrier properties. Changes in the carrier concentration related to the introduction of Eu lead to higher resistivity. A zT of ∼0.67 at 523 K is demonstrated for Yb 1.6Eu 0.4CdSb 2 due to its high Seebeck, moderate electrical resistivity, and very low thermal conductivity.« less

Authors:
 [1];  [1];  [1]; ORCiD logo [2];  [1];  [3];  [3]; ORCiD logo [1]
  1. Univ. of California, Davis, CA (United States)
  2. Univ. of California, Davis, CA (United States); Basque Foundation for Science, Bilbao (Spain)
  3. Colorado School of Mines, Golden, CO (United States)
Publication Date:
Research Org.:
Univ. of California, Davis, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
Contributing Org.:
National Energy Research Scientific Computing Center
OSTI Identifier:
1416091
Alternate Identifier(s):
OSTI ID: 1508301
Grant/Contract Number:  
NA0002908; AC02-05CH11231
Resource Type:
Published Article
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 30; Journal Issue: 2; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Cooley, Joya A., Promkhan, Phichit, Gangopadhyay, Shruba, Donadio, Davide, Pickett, Warren E., Ortiz, Brenden R., Toberer, Eric S., and Kauzlarich, Susan M. High Seebeck Coefficient and Unusually Low Thermal Conductivity Near Ambient Temperatures in Layered Compound Yb2–xEuxCdSb2. United States: N. p., 2017. Web. doi:10.1021/acs.chemmater.7b04517.
Cooley, Joya A., Promkhan, Phichit, Gangopadhyay, Shruba, Donadio, Davide, Pickett, Warren E., Ortiz, Brenden R., Toberer, Eric S., & Kauzlarich, Susan M. High Seebeck Coefficient and Unusually Low Thermal Conductivity Near Ambient Temperatures in Layered Compound Yb2–xEuxCdSb2. United States. doi:10.1021/acs.chemmater.7b04517.
Cooley, Joya A., Promkhan, Phichit, Gangopadhyay, Shruba, Donadio, Davide, Pickett, Warren E., Ortiz, Brenden R., Toberer, Eric S., and Kauzlarich, Susan M. Mon . "High Seebeck Coefficient and Unusually Low Thermal Conductivity Near Ambient Temperatures in Layered Compound Yb2–xEuxCdSb2". United States. doi:10.1021/acs.chemmater.7b04517.
@article{osti_1416091,
title = {High Seebeck Coefficient and Unusually Low Thermal Conductivity Near Ambient Temperatures in Layered Compound Yb2–xEuxCdSb2},
author = {Cooley, Joya A. and Promkhan, Phichit and Gangopadhyay, Shruba and Donadio, Davide and Pickett, Warren E. and Ortiz, Brenden R. and Toberer, Eric S. and Kauzlarich, Susan M.},
abstractNote = {Zintl phases are promising thermoelectric materials because they are composed of both ionic and covalent bonding, which can be independently tuned. An efficient thermoelectric material would have regions of the structure composed of a high-mobility compound semiconductor that provides the “electron–crystal” electronic structure, interwoven (on the atomic scale) with a phonon transport inhibiting structure to act as the “phonon–glass”. The phonon–glass region would benefit from disorder and therefore would be ideal to house dopants without disrupting the electron–crystal region. The solid solution of the Zintl phase, Yb2–xEuxCdSb2, presents such an optimal structure, and here we characterize its thermoelectric properties above room temperature. Thermoelectric property measurements from 348 to 523 K show high Seebeck values (maximum of ∼269 μV/K at 523 K) with exceptionally low thermal conductivity (minimum ∼0.26 W/m K at 473 K) measured via laser flash analysis. Speed of sound data provide additional support for the low thermal conductivity. Density functional theory (DFT) was employed to determine the electronic structure and transport properties of Yb2CdSb2 and YbEuCdSb2. Lanthanide compounds display an f-band well below (∼2 eV) the gap. This energy separation implies that f-orbitals are a silent player in thermoelectric properties; however, we find that some hybridization extends to the bottom of the gap and somewhat renormalizes hole carrier properties. Changes in the carrier concentration related to the introduction of Eu lead to higher resistivity. A zT of ∼0.67 at 523 K is demonstrated for Yb1.6Eu0.4CdSb2 due to its high Seebeck, moderate electrical resistivity, and very low thermal conductivity.},
doi = {10.1021/acs.chemmater.7b04517},
journal = {Chemistry of Materials},
number = 2,
volume = 30,
place = {United States},
year = {2017},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1021/acs.chemmater.7b04517

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