Interfacial engineering of ZnO/PVDF-PP nanocomposites via Al2O3 as an interlayer towards elevated dielectric properties

High dielectric permittivity (ε) but low loss polymeric composites have presented wide applications. To elevate the overall dielectric performances in raw zinc oxide (ZnO)/polyvinylidene fluoride (PVDF), the prepared aluminum oxide (Al2O3) encapsulated ZnO core-shell particles were incorporated into the polypropylene (PP) modified PVDF blend to generate high ε and breakdown strength (Eb) but low loss nanocomposites. The Al2O3 shell’ impacts on the dielectric performances of the ZnO/PVDF-PP were investigated. The results indicate that the insulating Al2O3 shell induces concurrent interparticle polarization and intraparticle polarization leading to evidently enhanced ε, and effectively restrains the leakage current resulting in simultaneously suppressed loss and elevated Eb in the nanocomposites. Further, the introduced alumina shell can induce traps and capture charge carrier thus resulting in enhanced Eb. Through facilitating the intra-particle polarization and repressing the charge migration, the 50 wt% ZnO@Al2O3/PP-PVDF present a much higher ε (16) and Eb (11 kV/mm) but lower dielectric loss (0.08), respectively, far exceeding 9.6, 9 kV/mm and 0.18 at 100 Hz for the unmodified ZnO nanocomposites. Further, the dielectric parameters of the nanocomposites can be effectively tuned via tailoring the Al2O3 shell thickness. The fitting via the Havriliak-Negami equation theoretically interpret the experimental results and uncover the underlying multiple polarization mechanisms. This work provides deep insight into the design and development of flexible polymeric nanodielectrics with eminent integrated dielectric properties for appealing applications in electronic device and power system.