Hoisting high-field breakdown strength in CCTO/PVDF composites via introducing high insulating alumina interlayer

Polymer composites combining high dielectric permittivity ( ε ), low dielectric loss, and superior breakdown strength ( E b ) exhibit significant industrial application prospects. To achieve excellent overall dielectric properties in calcium copper titanate (CCTO)/poly (vinylidene fluoride, PVDF) composites, the alumina (Al 2 O 3 ) encapsulated CCTO particles were prepared via a sol-gel technology and subsequently added into PVDF to explore the interlayer’ impact on the morphology and dielectric performance. The results demonstrate that the Al 2 O 3 shell simultaneously improves interfacial compatibility between the two components and thereby reduces both dielectric loss and electrical conductivity in the CCTO@Al 2 O 3 /PVDF. Moreover, the CCTO@Al 2 O 3 /PVDF composites showcase superior E b relative to pure CCTO/PVDF, as the Al 2 O 3 interlayer homogenizes the electric field distribution by mitigating dielectric mismatch and introduces charge-trapping sites that restrict carrier mobility, thereby mitigating electric field distortion and inhibiting electrical tree growth. Precise regulation and control of the Al 2 O 3 thickness enables effective tuning of the overall dielectric properties in CCTO@Al 2 O 3 /PVDF composites. Theoretical analysis unlocks the fundamental polarization mechanisms and the modulated charge transport behavior in modified CCTO/PVDF composites. This study establishes a novel strategy for developing flexible polymer dielectrics combining concurrently high E b and ε , coupled with low loss, presenting promising application prospects in power electronics and high-voltage insulation systems.