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.

Transmission electron microscopy was performed on a carbon‐containing SiOC material derived from a polymer precursor pyrolyzed at 1100°C and subsequently annealed at 1400°C. The TEM study focused on the correlation between micro/nanostructure evolution and the piezoresistivity monitored on the annealed sample. Upon pyrolysis, the material was completely amorphous with no local crystallization of the thermodynamically stable phases. Upon annealing, however, the formation of turbostratic carbon and SiC was observed. Unexpectedly, crystallization only occurred within intrinsic pores while the bulk of the sample remained amorphous. As the nanopores formed a percolation network throughout the entire material, the piezoresistive effect is predominantly a consequence of turbostratic carbon formation inside the residual porosity.