Effects of excess carbon and vibrational properties in ultrafine SiC powders
Charpentier, S.; Kassiba, A.; Bulou, A.; Monthioux, M.; Cauchetier, M.; Charpentier S.; Laboratoire de Physique de l'état condensé (UPRES-A CNRS 6087), Université du Maine, Faculté des Sciences, avenue Olivier Messiaen, 72085 Le Mans Cedex 09, France; Kassiba A.; Laboratoire de Physique de l'état condensé (UPRES-A CNRS 6087), Université du Maine, Faculté des Sciences, avenue Olivier Messiaen, 72085 Le Mans Cedex 09, France; Bulou A.; Laboratoire de Physique de l'état condensé (UPRES-A CNRS 6087), Université du Maine, Faculté des Sciences, avenue Olivier Messiaen, 72085 Le Mans Cedex 09, France; Monthioux M.; CEMES (UPR CNRS 8011), B.P. 4347, 29 rue Jeanne Marvig, 31055 Toulouse Cedex, France; Cauchetier M.; CEA-DRECAM, Service des Photons Atomes et Molécules, CE Saclay, 91191 Gif-sur-Yvette Cedex, France
Журнал:
The European Physical Journal Applied Physics
Дата:
1999
Аннотация:
Structural and vibrational properties are investigated in SiC nanopowders synthesized by a CO<sub>2</sub> laser pyrolysis of (SiH<sub>4</sub>, C<sub>2</sub>H<sub>2</sub>) gaseous mixture and thermally treated up to 1800 °C. The structural modifications of the SiC crystallites and the arrangement of the carbon in excess are monitored at different annealing stages. A critical behaviour is revealed in the powder annealed at T <sub>a</sub> = 1500 °C through the features of the Raman spectra and the insulating-conductor transition. The significant electric conductivity (σ ≈ 0.05 S cm<sup>−1</sup>) which appears above T <sub>a</sub> is discussed with respect to the powder composition and the interface effects where the carbon in excess seems to play a key role.
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