Influence of the acceptor-fillers on the dielectric properties of polyimide composites

High-performance polymer dielectrics are critical for high-tech fields such as electrical insulation and aerospace. Nevertheless, it is still challenging to achieve simultaneous improvements in both dielectric constant and breakdown strength in polymer dielectrics. In this work, Al3+ substitution Si4+ in SiO2 by high-temperature sintering to create hole traps to obtain the acceptor-doped fillers Si1-0.75xAlxO2 (SA (x mol%)), and polyimide (PI) dielectric containing SA fillers with different contents were synthesized using in-situ polymerization. The hole traps in the fillers modulate the electrical behavior of the polymer dielectric, thereby significantly increasing the dielectric constant and breakdown strength by modulating the polarization behavior and capture carriers. Among them, the dielectric constant of the 1.25 vol% SA (1.5 mol%)/PI composite was increased to 3.60 at 1 Hz, and the breakdown strength Eb reached 581.5 kV/mm. This work provides a new synthesis strategy for simultaneously achieving high insulation and high polarization of polymer dielectric.