Piezoresistive effect in SiOC ceramics for integrated pressure sensors

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.