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Microscopic Origin of the Composition-Dependent Change of the Thermal Conductivity in Boron Carbides

Published online by Cambridge University Press:  25 February 2011

David Emin ,
I. A. Howard ,
T. A. Green  and
C. L. Beckel
David Emin
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA.
I. A. Howard
Affiliation:
Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico, 87131, USA Presently at the Department of Physics, Queen Mary College, University of London, Mile End Road, London El 4NS, UK
T. A. Green
Affiliation:
Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA.
C. L. Beckel
Affiliation:
Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico, 87131, USA
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Abstract

Large grain polycrystalline boron carbides have a high-temperature thermal conductivity which changes from being characteristic of a crystal to being glass-like as the carbon content is reduced from its maximal value. We relate this phenomenon, to compositional changes within the three-atom intericosahedral chains. With a reduction of the carbon concentration from its maximal concentration (20 %), a carbon atom within some of the three-atom (CBC) intericosahedral chains is replaced by a boron atom, thereby producing CBB chains. We estimate that the CBB chains are significantly softer than the CBC chains. Thus, with this reduction of carbon content the intericosahedral chains are inhomogeneously softened. This suppresses the coherent transport of heat through the chains. The remaining thermal transport occurs incoherently through vibrationally inequivalent structural units, i.e. “phonon hopping.”

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 97: Symposium I – Novel Refractory Semiconductors , 1987 , 83
Copyright
Copyright © Materials Research Society 1987

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References

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