2015-Sustainable Industrial Processing Summit
SIPS 2015 Volume 8: Composite & Ceramic, Quasi-crystals and Nanomaterials

Editors:Kongoli F, Pech-Canul M, Kalemtas A, Werheit H
Publisher:Flogen Star OUTREACH
Publication Year:2015
Pages:300 pages
ISBN:978-1-987820-31-7
ISSN:2291-1227 (Metals and Materials Processing in a Clean Environment Series)
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    Phase Transition and Isotope-Induced Phonon Softening in natB4.3C Boron Carbide at Moderate Temperatures

    Helmut Werheit1; Stefan Hoffmann2; Guido Gerlach3; Andreas Leithe-Jasper4; Takao Tanaka5;
    1UNIVERSITY DUISBURG-ESSEN, Koeln, Germany (Deutschland); 2MAX-PLANCK-INSTITUTE FOR CHEMICAL PHYSICS OF SOLIDS, Dresden, Germany; 3UNIVERSITY DUISBURG-ESSEN, Duisburg, Germany; 4MAX-PLANCK INSTITUT FUR DIE CHEMISCHE PHYSIK FESTER STOFFE, Dresden, Germany (Deutschland); 5NIMS, Tsukuba, Japan;
    Type of Paper: Regular
    Id Paper: 281
    Topic: 18

    Abstract:

    Additional coauthors (without e-mail address: Stefan Hoffmann; Guido Gerlach)<br />A recent theoretical structure model of carbon-rich boron carbide (Yaoa et al.) assumes a continuous phase transition accompanied by loss of inversion symmetry near 790K and a first-order transition at 717 K, breaking the 3-fold rotational symmetry. We checked this model by experiment, performing DSC measurements on single crystal B4.3C. A clear anomaly at 712 K, close to the theoretically predicted phase transition, has exothermic character, opposite to the endothermic one predicted. Phonon splitting between 700 and 800 K indicates structural changes. The IR-active vibration of the bending mode of the C-B-C chains between 100 and 800 K shows additional anomalies between 400 and 500 K: the distribution of isotopes on the B(3) site changes drastically, accompanied by a considerable lattice softening.

    Keywords:

    boron carbide; phase transition;DSC measurements;phonon; isotope distribution

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    Cite this article as:

    Werheit H, Hoffmann S, Gerlach G, Leithe-Jasper A, Tanaka T. Phase Transition and Isotope-Induced Phonon Softening in natB4.3C Boron Carbide at Moderate Temperatures. In: Kongoli F, Pech-Canul M, Kalemtas A, Werheit H, editors. Sustainable Industrial Processing Summit SIPS 2015 Volume 8: Composite & Ceramic, Quasi-crystals and Nanomaterials. Volume 8. Montreal(Canada): FLOGEN Star Outreach. 2015. p. 183-192.