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Updated: Mar 27, 2026
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Negative Additive Manufacturing of Complex Shaped Boron Carbides
Published on: September 18, 2018
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High-pressure phase transition makes B4.3C boron carbide a wide-gap semiconductor
Anwar Hushur1, Murli H Manghnani, Helmut Werheit
1University of Hawaii, Hawaii Institute of Geophysics and Planetology, Honolulu, HI 96822, USA.
Summary
High pressure transforms boron carbide into a wide-gap semiconductor. Structural defects decrease, leading to increased transparency and a band gap of ~3.5 eV above 60 GPa.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Solid-State Chemistry
Background:
- Boron carbide (B4.3C) exhibits complex electronic and optical properties influenced by structural defects.
- Understanding its behavior under extreme conditions is crucial for potential applications.
Purpose of the Study:
- To investigate the pressure-induced evolution of atomic distances, optical properties, and Raman-active phonons in single-crystal boron carbide up to ~70 GPa.
- To elucidate the relationship between structural changes, defect concentration, and electronic band gap under high pressure.
Main Methods:
- High-pressure experiments utilizing diamond anvil cells.
- Optical spectroscopy to measure transparency and band gap.
- Raman spectroscopy to probe phonon modes and structural transitions.
Main Results:
- An anomalous increase in optical transparency was observed, rapidly accelerating around 55 GPa.
- Full visible optical transparency was approached above 60 GPa, indicating a band gap of ~3.5 eV.
- A pressure-dependent phase transition near 40 GPa was identified, likely involving C-B-C chains, while the icosahedral structure remained largely intact.
- The concentration of electronic-property-controlling defects decreased with increasing pressure, vanishing at high pressures.
Conclusions:
- Boron carbide transitions to a wide-gap semiconductor under high pressure.
- The observed changes are attributed to the reduction and eventual elimination of structural defects.
- A phase transition near 40 GPa influences the material's properties.
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