Double-Interlayer SiO2@PDA Induces Multiple Polarizations and Deep Traps in CCTO/PVDF Composites toward Concurrently Elevated Permittivity and Breakdown Strength.

Polymer composites possessing high dielectric permittivity (ε), low dielectric loss (tanδ) and outstanding breakdown strength (Eb) hold vast application potential in electronic devices and electrical equipment. To achieve synergistic enhancement of ε and Eb in CCTO (copper calcium titanate)/PVDF (polyvinylidene fluoride), raw CCTO particles were coated with SiO2 (silica) and PDA (polydopamine), respectively, and the modified CCTO were blended with PVDF to probe the double-shell' effect on the morphology and dielectric performances of the composites. The results reveal that the CCTO@SiO2@PDA/PVDF achieves improved ε and Eb alongside reduced tanδ compared with CCTO/PVDF composites. The enhanced ε originates from the constructed double-shell that facilitates intra-particle polarization while limiting inter-particle polarization, and creates deep traps to restrain tanδ and conductivity. This double-shell is capable of reinforcing interfacial bonding between CCTO and PVDF while mitigating interfacial dielectric mismatch. Local electric field distortion gets weakened and electrical tree growth becomes suppressed accordingly, which finally boosts the Eb. Theoretical calculations and simulations disclose the multiple polarization mechanisms and modified charge transport behaviors within the CCTO@SiO2@PDA/PVDF. This work puts forward a strategy to fabricate polymer composites with high Eb and ε, low tanδ, displaying extensive applications in pulse power devices and electrical insulating fields.