Comparative study on piezoresistive performance and high-temperature stability of three typical metal-modified SiOC ceramics

Piezoresistive sensors are widely used in industrial production and daily life. However, prolonged exposure to high-temperature environments can promote the graphitization of microcrystalline carbon and the growth of carbon clusters, leading to a weakening of the free carbon percolation effect and a degradation of the material's piezoresistive properties. As a result, they are less suitable for extreme environments. In this study, SiOC-based ceramics were selected to investigate the effects of transition metal doping on the performance of polymer-derived ceramic (PDC) materials under long-term high-temperature conditions. Fe, Co, and Ti were chosen for equivalent doping. When subjected to a short heat treatment duration (2 h) at 1400 °C, doping facilitated the tunneling effect, enhancing the performance and piezoresistive sensitivity of the sensing materials. Among them, the SiOC/Fe system exhibited the best performance, with a resistivity change rate of 84.62 % and a sensitivity of 3.390 MPa⁻¹. When the heat treatment duration was extended to 8 h, the resistivity changes rates of the SiOC/Fe, SiOC/Co, and SiOC/Ti systems decreased by 54.48 %, 35.17 %, and 5.8 %, respectively. The Ti-doped system maintained better response sensitivity, indicating that Ti effectively optimized the piezoresistive performance of the SiOC-based materials under high-temperature conditions.