Leveraging counteractive temperature-dependent resistivity among components for temperature-insensitive electromagnetic characteristics in lightweight SiOCN ceramics

The rapid advancement of aerospace technology has subjected high-speed aircraft to increasingly severe high-temperature conditions, thereby substantially increasing the demand for high-temperature electromagnetic wave (EMW) absorbing materials. However, due to the temperature dependence of the permittivity, high-temperature EMW absorbing materials still face the challenge of maintaining consistent impedance matching performance at different temperatures. This study proposes a novel approach by in-situ constructing Si-Co alloys in amorphous SiOCN ceramics, taking advantage of the inverse temperature-dependent resistivity behavior among components to dynamically equilibrate the overall conductivity of the ceramics, thereby achieving temperature-insensitive permittivity. This strategy significantly enhances the robustness of dielectric properties against temperature fluctuations and enables effective EMW absorption within a temperature range from ambient to 800 °C at low thickness. By using the self-sacrificing template method, a porous structure was formed while ensuring the precise shaping, thereby further achieving the lightweighting of the ceramics. This lightweight dielectric ceramic with temperature-insensitive permittivity provides novel perspectives for the development of wide-temperature-range EMW absorbing materials.