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Title: High-pressure phase transition makes B 4.3 C boron carbide a wide-gap semiconductor

Single-crystal B4.3C boron carbide is investigated concerning the pressure-dependence of optical properties and of Raman-active phonons up to ~70 GPa. The high concentration of structural defects determining the electronic properties of boron carbide at ambient conditions initially decrease and finally vanish with pressure increasing. We obtain this immediately from transparency photos, allowing to estimate the pressure-dependent variation of the absorption edge rapidly increasing around 55 GPa. Glass-like transparency at pressures exceeding 60 GPa indicate that the width of the band exceeds ~3.1 eV thus making boron carbide a wide-gap semiconductor. Furthermore, the spectra of Raman–active phonons indicate a pressure-dependent phase transition in single-crystal natB4.3C boron carbide near 35 GPa., particularly related to structural changes in connection with the C-B-C chains, while the basic icosahedral structure remains largely unaffected.
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [4]
  1. Xinjiang Univ. (China). Dept. of Physical Science and Technology; Univ. of Hawaii, Honolulu, HI (United States). Hawaii Inst. of Geophysics and Planteology
  2. Univ. of Hawaii, Honolulu, HI (United States). Hawaii Inst. of Geophysics and Planteology
  3. Univ. of Duisburg (Germany). Experimental Physics
  4. Univ. of California, Santa Cruz, CA (United States). Dept. of Earth and Planetary Sciences
Publication Date:
Grant/Contract Number:
NA0002006; EAR-0957137
Type:
Accepted Manuscript
Journal Name:
Journal of Physics. Condensed Matter
Additional Journal Information:
Journal Volume: 28; Journal Issue: 4; Journal ID: ISSN 0953-8984
Publisher:
IOP Publishing
Research Org:
Carnegie Inst. of Washington, Argonne, IL (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; boron carbide; high pressure; phase transition; Raman-active phonons; electronic structure
OSTI Identifier:
1379177