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Title: Pseudogap and anharmonic phonon behavior in Ba{sub 8}Ga{sub 16}Ge{sub 30}: An NMR study

Abstract

We have performed {sup 69}Ga, {sup 71}Ga, and {sup 137}Ba NMR on Ba{sub 8}Ga{sub 16}Ge{sub 30}, a clathrate semiconductor which has been of considerable interest due to its large figure of merit for thermoelectric applications. In measurements from 4 K to 450 K, we used measurements on the two Ga nuclei to separate the magnetic and electric quadrupole hyperfine contributions and thereby gain information about the metallic and phonon behavior. The results show the presence of a pseudogap in the Ga electronic states within the conduction band, superposed upon a large Ba contribution to the conduction band. Meanwhile the phonon contributions to the Ga relaxation rates are large and increase more rapidly with temperature than typical semiconductors. These results provide evidence for enhanced anharmonicity of the propagative phonon modes over a wide range, providing experimental evidence for enhanced phonon-phonon scattering as a mechanism for the reduced thermal conductivity.

Authors:
 [1];  [1];  [2]
  1. Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
22679033
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 145; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BARIUM 137; EXPERIMENTAL DATA; GALLIUM 71; NUCLEAR MAGNETIC RESONANCE; PHONONS; THERMAL CONDUCTIVITY

Citation Formats

Sirusi, Ali A., E-mail: alisirusi@tamu.edu, Ross, Joseph H., E-mail: jhross@tamu.edu, and Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843. Pseudogap and anharmonic phonon behavior in Ba{sub 8}Ga{sub 16}Ge{sub 30}: An NMR study. United States: N. p., 2016. Web. doi:10.1063/1.4960054.
Sirusi, Ali A., E-mail: alisirusi@tamu.edu, Ross, Joseph H., E-mail: jhross@tamu.edu, & Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843. Pseudogap and anharmonic phonon behavior in Ba{sub 8}Ga{sub 16}Ge{sub 30}: An NMR study. United States. doi:10.1063/1.4960054.
Sirusi, Ali A., E-mail: alisirusi@tamu.edu, Ross, Joseph H., E-mail: jhross@tamu.edu, and Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843. Sun . "Pseudogap and anharmonic phonon behavior in Ba{sub 8}Ga{sub 16}Ge{sub 30}: An NMR study". United States. doi:10.1063/1.4960054.
@article{osti_22679033,
title = {Pseudogap and anharmonic phonon behavior in Ba{sub 8}Ga{sub 16}Ge{sub 30}: An NMR study},
author = {Sirusi, Ali A., E-mail: alisirusi@tamu.edu and Ross, Joseph H., E-mail: jhross@tamu.edu and Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843},
abstractNote = {We have performed {sup 69}Ga, {sup 71}Ga, and {sup 137}Ba NMR on Ba{sub 8}Ga{sub 16}Ge{sub 30}, a clathrate semiconductor which has been of considerable interest due to its large figure of merit for thermoelectric applications. In measurements from 4 K to 450 K, we used measurements on the two Ga nuclei to separate the magnetic and electric quadrupole hyperfine contributions and thereby gain information about the metallic and phonon behavior. The results show the presence of a pseudogap in the Ga electronic states within the conduction band, superposed upon a large Ba contribution to the conduction band. Meanwhile the phonon contributions to the Ga relaxation rates are large and increase more rapidly with temperature than typical semiconductors. These results provide evidence for enhanced anharmonicity of the propagative phonon modes over a wide range, providing experimental evidence for enhanced phonon-phonon scattering as a mechanism for the reduced thermal conductivity.},
doi = {10.1063/1.4960054},
journal = {Journal of Chemical Physics},
number = 5,
volume = 145,
place = {United States},
year = {Sun Aug 07 00:00:00 EDT 2016},
month = {Sun Aug 07 00:00:00 EDT 2016}
}