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High-Temperature Raman Spectroscopy of Nano-Crystalline Carbon in Silicon Oxycarbide

Rosenburg, Felix and Ionescu, Emanuel and Nicoloso, Norbert and Riedel, Ralf (2018):
High-Temperature Raman Spectroscopy of Nano-Crystalline Carbon in Silicon Oxycarbide.
In: Materials, MDPI, p. 93, 11, (1), ISSN 1996-1944,
DOI: 10.3390/ma11010093,
[Online-Edition: https://doi.org/10.3390/ma11010093],
[Article]

Abstract

The microstructure of segregated carbon in silicon oxycarbide (SiOC), hot-pressed at T = 1600 °C and p = 50 MPa, has been investigated by VIS Raman spectroscopy (λ = 514 nm) within the temperature range 25–1000 °C in air. The occurrence of the G, D’ and D bands at 1590, 1620 and 1350 cm−1, together with a lateral crystal size La < 10 nm and an average distance between lattice defects LD ≈ 8 nm, provides evidence that carbon exists as nano-crystalline phase in SiOC containing 11 and 17 vol % carbon. Both samples show a linear red shift of the G band up to the highest temperature applied, which is in agreement with the description of the anharmonic contribution to the lattice potential by the modified Tersoff potential. The temperature coefficient χG = −0.024 ± 0.001 cm−1/°C is close to that of disordered carbon, e.g., carbon nanowalls or commercial activated graphite. The line width of the G band is independent of temperature with FWHM-values of 35 cm−1 (C-11) and 45 cm−1 (C-17), suggesting that scattering with defects and impurities outweighs the phonon-phonon and phonon-electron interactions. Analysis of the Raman line intensities indicates vacancies as dominating defects.

Item Type: Article
Erschienen: 2018
Creators: Rosenburg, Felix and Ionescu, Emanuel and Nicoloso, Norbert and Riedel, Ralf
Title: High-Temperature Raman Spectroscopy of Nano-Crystalline Carbon in Silicon Oxycarbide
Language: English
Abstract:

The microstructure of segregated carbon in silicon oxycarbide (SiOC), hot-pressed at T = 1600 °C and p = 50 MPa, has been investigated by VIS Raman spectroscopy (λ = 514 nm) within the temperature range 25–1000 °C in air. The occurrence of the G, D’ and D bands at 1590, 1620 and 1350 cm−1, together with a lateral crystal size La < 10 nm and an average distance between lattice defects LD ≈ 8 nm, provides evidence that carbon exists as nano-crystalline phase in SiOC containing 11 and 17 vol % carbon. Both samples show a linear red shift of the G band up to the highest temperature applied, which is in agreement with the description of the anharmonic contribution to the lattice potential by the modified Tersoff potential. The temperature coefficient χG = −0.024 ± 0.001 cm−1/°C is close to that of disordered carbon, e.g., carbon nanowalls or commercial activated graphite. The line width of the G band is independent of temperature with FWHM-values of 35 cm−1 (C-11) and 45 cm−1 (C-17), suggesting that scattering with defects and impurities outweighs the phonon-phonon and phonon-electron interactions. Analysis of the Raman line intensities indicates vacancies as dominating defects.

Journal or Publication Title: Materials
Volume: 11
Number: 1
Publisher: MDPI
Uncontrolled Keywords: polymer-derived ceramics, Raman spectroscopy, anharmonicity, carbon, defects
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 15 Jan 2018 09:10
DOI: 10.3390/ma11010093
Official URL: https://doi.org/10.3390/ma11010093
Funders: The authors gratefully acknowledge financial support by theDeutsche Forschungsgemeinschaft
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