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°C exhibits high piezoresistivity, leading to strain sensitivities (k factors) of ∼145, while lower pyrolysis temperatures (1000°–1300°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.