Gold-Nanoparticle-Deposited TiO2 Nanorod/Poly(Vinylidene Fluoride) Composites with Enhanced Dielectric Performance

Flexible dielectric polymer composites have been of great interest as embedded capacitor materials in the electronic industry. However, a polymer composite has a low relative dielectric permittivity (epsilon' < 100), while its dielectric loss tangent is generally large (tan delta > 0.1). In this study, we fabricate a novel, high-permittivity polymer nanocomposite system with a low tan delta. The nanocomposite system comprises poly(vinylidene fluoride) (PVDF) co-filled with Au nanoparticles and semiconducting TiO2 nanorods (TNRs) that contain Ti3+ ions. To homogeneously disperse the conductive Au phase, the TNR surface was decorated with Au-NPs similar to 10-20 nm in size (Au-TNRs) using a modified Turkevich method. The polar beta-PVDF phase was enhanced by the incorporation of the Au nanoparticles, partially contributing to the enhanced epsilon' value. The introduction of the Au-TNRs in the PVDF matrix provided three-phase Au-TNR/PVDF nanocomposites with excellent dielectric properties (i.e., high epsilon' approximate to 157 and low tan delta approximate to 0.05 at 1.8 vol% of Au and 47.4 vol% of TNRs). The epsilon' of the three-phase Au-TNR/PVDF composite is similar to 2.4-times higher than that of the two-phase TNR/PVDF composite, clearly highlighting the primary contribution of the Au nanoparticles at similar filler loadings. The volume fraction dependence of epsilon' is in close agreement with the effective medium percolation theory model. The significant enhancement in epsilon' was primarily caused by interfacial polarization at the PVDF-conducting Au nanoparticle and PVDF-semiconducting TNR interfaces, as well as by the induced beta-PVDF phase. A low tan delta was achieved due to the inhibited conducting pathway formed by direct Au nanoparticle contact.