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Title: Lattice dynamics and elasticity in thermoelectric Mg 2 Si 1 - x Sn x

Abstract

Lattice dynamics and elastic constants in Mg 2Si 1-xSn x were investigated using resonant ultrasound spectroscopy, Mossbauer spectroscopy, nuclear inelastic scattering, and inelastic x-ray scattering. Increasing the Sn content x results in smaller elastic constants, lower Sn specific Debye temperature, lower speed of sound, and a softening of acoustic Sn specific phonons. However, close to band convergence at about x = 0.6, the shear modulus is well below the expected value, which suggests a pronounced connection between band convergence and lattice dynamics in this system. Based on the determined speed of sound and average phonon group velocity, the importance of optical phonons for lattice thermal conductivity is discussed, as the significant reduction in both velocities would yield an implausibly low lattice thermal conductivity of only about 60% of the experimental value. Sn specific thermodynamic quantities calculated from the Sn specific density of phonon states substantiate the general softening of lattice vibrations upon substitution of Si by Sn. A major contribution to the vibrational entropy is thus due to Sn specific vibrational modes. The generalized density of phonon states in Mg 2Si 1-xSn x derived from inelastic x-ray scattering for one composition shows that vibrational modes related to lightweight Mg andmore » Si set in above 12.5 meV, whereas Sn specific modes are concentrated around 11 meV.« less

Authors:
 [1];  [2];  [3];  [3];  [1];  [4]
  1. Julich Research Centre (Germany). Julich Centre for Neutron Science (JCNS)
  2. German Aerospace Center, Koln (Germany)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1502500
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 3; Journal Issue: 2; Journal ID: ISSN 2475-9953
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Klobes, Benedikt, de Boor, Johannes, Alatas, Ahmet, Hu, Michael Y., Simon, Ronnie E., and Hermann, Raphaël P. Lattice dynamics and elasticity in thermoelectric Mg2Si1-xSnx. United States: N. p., 2019. Web. doi:10.1103/PhysRevMaterials.3.025404.
Klobes, Benedikt, de Boor, Johannes, Alatas, Ahmet, Hu, Michael Y., Simon, Ronnie E., & Hermann, Raphaël P. Lattice dynamics and elasticity in thermoelectric Mg2Si1-xSnx. United States. doi:10.1103/PhysRevMaterials.3.025404.
Klobes, Benedikt, de Boor, Johannes, Alatas, Ahmet, Hu, Michael Y., Simon, Ronnie E., and Hermann, Raphaël P. Thu . "Lattice dynamics and elasticity in thermoelectric Mg2Si1-xSnx". United States. doi:10.1103/PhysRevMaterials.3.025404.
@article{osti_1502500,
title = {Lattice dynamics and elasticity in thermoelectric Mg2Si1-xSnx},
author = {Klobes, Benedikt and de Boor, Johannes and Alatas, Ahmet and Hu, Michael Y. and Simon, Ronnie E. and Hermann, Raphaël P.},
abstractNote = {Lattice dynamics and elastic constants in Mg2Si1-xSnx were investigated using resonant ultrasound spectroscopy, Mossbauer spectroscopy, nuclear inelastic scattering, and inelastic x-ray scattering. Increasing the Sn content x results in smaller elastic constants, lower Sn specific Debye temperature, lower speed of sound, and a softening of acoustic Sn specific phonons. However, close to band convergence at about x = 0.6, the shear modulus is well below the expected value, which suggests a pronounced connection between band convergence and lattice dynamics in this system. Based on the determined speed of sound and average phonon group velocity, the importance of optical phonons for lattice thermal conductivity is discussed, as the significant reduction in both velocities would yield an implausibly low lattice thermal conductivity of only about 60% of the experimental value. Sn specific thermodynamic quantities calculated from the Sn specific density of phonon states substantiate the general softening of lattice vibrations upon substitution of Si by Sn. A major contribution to the vibrational entropy is thus due to Sn specific vibrational modes. The generalized density of phonon states in Mg2Si1-xSnx derived from inelastic x-ray scattering for one composition shows that vibrational modes related to lightweight Mg and Si set in above 12.5 meV, whereas Sn specific modes are concentrated around 11 meV.},
doi = {10.1103/PhysRevMaterials.3.025404},
journal = {Physical Review Materials},
issn = {2475-9953},
number = 2,
volume = 3,
place = {United States},
year = {2019},
month = {2}
}

Journal Article:
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Works referenced in this record:

Convergence of electronic bands for high performance bulk thermoelectrics
journal, May 2011

  • Pei, Yanzhong; Shi, Xiaoya; LaLonde, Aaron
  • Nature, Vol. 473, Issue 7345, p. 66-69
  • DOI: 10.1038/nature09996