Effect of Nano Silver Modification on the Dielectric Properties of Ag@TiO2/PVDF Composites

To get a dielectric material with a high dielectric permittivity and suppressed dielectric loss, nano-Ag with a particle size of 20 nm and Ag@TiO2 core-shell particles with diameters of approximately 70–120 nm were embedded in polyvinylidene fluoride (PVDF) to fabricate nano-Ag/Ag@TiO2/PVDF composites. After being modified by nano-Ag with 3 vol% optimal amount, the relative permittivity (εr) at 100 Hz of 50 vol% Ag@TiO2/PVDF composites was 61, and the dielectric loss can be suppressed to 0.04, almost 96.4% lower than that of unmodified composites, and a higher frequency stability of both εr and loss has also been found. The underlying mechanism of the reduced loss was attributed to Maxwell-Wagner polarization and the Coulomb blockade effect caused by the introduction of a small amount of nano-Ag, which will block the movement of electrons between metal nanoparticles and composites. The space charge polarization and conductance loss are weakened at lower and higher Ag@TiO2 filling ratios, respectively, thus leading to a very low loss of the composites.