Enhanced dielectric constant and breakdown strength in dielectric composites using TiO2@HfO2 nanowires with gradient dielectric constant

To investigate the influence of modification of ceramic fillers on the dielectric properties of polymer-based composites, TiO2 and core-shell structured TiO2@HfO2 nanowires were synthesized, and investigated in this study. TiO2 nanowires/polyvinylidene fluoride (PVDF) and TiO2@HfO2 nanowires/PVDF nanocomposites were prepared using the solution casting method. The experimental results showed that the TiO2@HfO2 nanowires/PVDF composites had improved dielectric properties compared with that of the TiO2 nanowires/PVDF composites. Owing to the enhanced interfacial polarisation by the multilevel interface, the composites with 10 wt % TiO2@HfO2 nanowires achieved the highest permittivity of 12.56 at 1 kHz, which was enhanced by ∼72% compared to the PVDF matrix. The electric field was evenly distributed by building the fillers with a gradient dielectric constant. The characteristic breakdown strength of the composite with 5 wt % TiO2@HfO2 reached 377.76 kV/mm, compared with that of 334.37 kV/mm for the composite with 5 wt % TiO2 nanowires. This study initiated a novel strategy for preparing dielectrics with high dielectric constant and improved breakdown strength.