Synthesis of Bulk BC8 Silicon Allotrope by Direct Transformation and Reduced-Pressure Chemical Pathways

Phase-pure samples of a metastable allotrope of silicon, Si–III or BC8, were synthesized by direct elemental transformation at 14 GPa and ∼900 K and also at significantly reduced pressure in the Na–Si system at 9.5 GPa by quenching from high temperatures ∼1000 K. Pure sintered polycrystalline ingots...

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Bibliographic Details
Published in:Inorganic chemistry 2016-09, Vol.55 (17), p.8943-8950
Main Authors: Kurakevych, Oleksandr O, Le Godec, Yann, Crichton, Wilson A, Guignard, Jérémy, Strobel, Timothy A, Zhang, Haidong, Liu, Hanyu, Coelho Diogo, Cristina, Polian, Alain, Menguy, Nicolas, Juhl, Stephen J, Gervais, Christel
Format: Article
Language:English
Subjects:
catalysis (heterogeneous)
charge transport
Chemical Sciences
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
energy storage (including batteries and capacitors)
hydrogen and fuel cells
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Material chemistry
materials and chemistry by design
MATERIALS SCIENCE
mesostructured materials
phonons
solar (photovoltaic)
superconductivity
synthesis (novel materials)
thermoelectric
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Summary:Phase-pure samples of a metastable allotrope of silicon, Si–III or BC8, were synthesized by direct elemental transformation at 14 GPa and ∼900 K and also at significantly reduced pressure in the Na–Si system at 9.5 GPa by quenching from high temperatures ∼1000 K. Pure sintered polycrystalline ingots with dimensions ranging from 0.5 to 2 mm can be easily recovered at ambient conditions. The chemical route also allowed us to decrease the synthetic pressures to as low as 7 GPa, while pressures required for direct phase transition in elemental silicon are significantly higher. In situ control of the synthetic protocol, using synchrotron radiation, allowed us to observe the underlying mechanism of chemical interactions and phase transformations in the Na–Si system. Detailed characterization of Si–III using X-ray diffraction, Raman spectroscopy, 29Si NMR spectroscopy, and transmission electron microscopy are discussed. These large-volume syntheses at significantly reduced pressures extend the range of possible future bulk characterization methods and applications.
ISSN:0020-1669
1520-510X
DOI:10.1021/acs.inorgchem.6b01443