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Piezoresistive effect in SiOC ceramics for integrated pressure sensors

: Riedel, R.; Toma, L.; Janssen, E.; Nuffer, J.; Melz, T.; Hanselka, H.


Journal of the American Ceramic Society 93 (2010), Nr.4, S.920-924
ISSN: 0002-7820
Fraunhofer LBF ()
sensor; ceramic

Piezoresistivity was found in silicon oxycarbide (SiOC) ceramics synthesized using a polymer-to-ceramic transformation process. A commercial polysiloxane, namely poly(methylsilsesquioxane), was used as the starting material. The SiOC ceramic synthesized at 1400 degrees C exhibits high piezoresistivity, leading to strain sensitivities (k factors) of similar to 145, while lower pyrolysis temperatures (1000 degrees-1300 degrees C) do not show a piezoresistive effect. Structural characterization by X-ray diffraction in combination with micro-Raman spectroscopy revealed that with increasing pyrolysis temperature, the content of free carbon in the X-ray amorphous SiOC matrix increases without changes in the overall composition. Percolation effects related to the carbon-based phase segregated from the SiOC matrix are responsible for the piezoresistivity analyzed in the SiOC ceramic.