Low-frequency dielectric performance of polyimide composites containing amorphous polymer-derived SiCN ceramics

High-dielectric-constant polymer-matrix composites have potential applications as embedded capacitors. In this paper, an amorphous polymer-derived SiCN ceramic was incorporated into a polyimide (PI) matrix by in situ polymerization for the first time. The resulting SiCN/PI composite showed good thermal stability below 500°C, with the SiCN filler being homogeneously dispersed in the PI matrix. The dielectric properties of the SiCN/PI composites were investigated over a broad frequency range (0.1-10⁶ Hz). The dielectric properties of the SiCN/PI composites at low frequencies revealed a weak percolation phenomenon similar to that shown by conductive/polymer composites and the calculated percolation threshold was 22.8 vol%. At SiCN loadings of 25 vol%, the SiCN/PI composites showed a high dielectric constant of 190 at 0.1 Hz, which is 57 times higher than that of pure PI (3.3). The conductivity of the 25 vol% SiCN/PI composite was as low as 8.5 × 10⁻¹⁰ S·cm⁻¹. These results could be explained by the unique microstructure of the polymer-derived SiCN ceramic, containing an amorphous Si matrix and a free carbon phase. This study revealed SiCN/PI composites as promising dielectric materials with promising applications in energy storage fields.