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Open AccessFeature PaperArticle

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

Institut für Material- und Geowissenschaften, Technische Universität Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt, Germany
Author to whom correspondence should be addressed.
Materials 2018, 11(1), 93;
Received: 5 December 2017 / Revised: 26 December 2017 / Accepted: 5 January 2018 / Published: 9 January 2018
(This article belongs to the Special Issue Polymer Derived Ceramics and Applications)
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. View Full-Text
Keywords: polymer-derived ceramics; Raman spectroscopy; anharmonicity; carbon; defects polymer-derived ceramics; Raman spectroscopy; anharmonicity; carbon; defects
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MDPI and ACS Style

Rosenburg, F.; Ionescu, E.; Nicoloso, N.; Riedel, R. High-Temperature Raman Spectroscopy of Nano-Crystalline Carbon in Silicon Oxycarbide. Materials 2018, 11, 93.

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