RESUMO
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 (ε' < 100), while its dielectric loss tangent is generally large (tanδ > 0.1). In this study, we fabricate a novel, high-permittivity polymer nanocomposite system with a low tanδ. 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 ~10-20 nm in size (Au-TNRs) using a modified Turkevich method. The polar ß-PVDF phase was enhanced by the incorporation of the Au nanoparticles, partially contributing to the enhanced ε' 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 ε' ≈ 157 and low tanδ ≈ 0.05 at 1.8 vol% of Au and 47.4 vol% of TNRs). The ε' of the three-phase Au-TNR/PVDF composite is ~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 ε' is in close agreement with the effective medium percolation theory model. The significant enhancement in ε' was primarily caused by interfacial polarization at the PVDF-conducting Au nanoparticle and PVDF-semiconducting TNR interfaces, as well as by the induced ß-PVDF phase. A low tanδ was achieved due to the inhibited conducting pathway formed by direct Au nanoparticle contact.
RESUMO
The enhanced dielectric permittivity (ε') while retaining a low loss tangent (tanδ) in silver nanoparticle-(In1/2Nb1/2)0.1Ti0.9O2/poly(vinylidene fluoride) (Ag-INTO/PVDF) composites with different volume fractions of a filler (fAg-INTO) was investigated. The hybrid particles were fabricated by coating Ag nanoparticles onto the surface of INTO particles, as confirmed by X-ray diffraction. The ε' of the Ag-INTO/PVDF composites could be significantly enhanced to ~86 at 1 kHz with a low tanδ of ~0.044. The enhanced ε' value was approximately >8-fold higher than that of the pure PVDF polymer for the composite with fAg-INTO = 0.5. Furthermore, ε' was nearly independent of frequency in the range of 102-106 Hz. Therefore, filling Ag-INTO hybrid particles into a PVDF matrix is an effective way to increase ε' while retaining a low tanδ of polymer composites. The effective medium percolation theory model can be used to fit the experimental ε' values with various fAg-INTO values. The greatly increased ε' primarily originated from interfacial polarization at the conducting Ag nanoparticle-PVDF and Ag-INTO interfaces, and it was partially contributed by the high ε' of INTO particles. A low tanδ was obtained because the formation of the conducting network in the polymer was inhibited by preventing the direct contact of Ag nanoparticles.
RESUMO
Three-phase gold nanoparticle-Na1/2Y1/2Cu3Ti4O12 (Au-NYCTO)/poly(vinylidene fluoride) (PVDF) composites with 0.095-0.487 hybrid particle volume fractions (f) were fabricated. Au nanoparticles with a diameter of â¼10 nm were decorated on the surfaces of high-permittivity NYCTO particles using a modified Turkevich's method. The polar ß-PVDF phase was confirmed to exist in the composites. Significantly enhanced dielectric permittivity of â¼98 (at 1 kHz) was obtained in the Au-NYCTO/PVDF composite with f Au-NYCTO = 0.487, while the loss tangent was suppressed to 0.09. Abrupt changes in the dielectric and electrical properties, which signified percolation behavior, were not observed even when f Au-NYCTO = 0.487. Using the effective medium percolation theory model, the percolation threshold (f c) was predicted to be at f Au-NYCTO = 0.69, at which f Au was estimated to â¼0.19 and close to the theoretical f c value for the conductor-insulator composites (f c = 0.16). A largely enhanced dielectric response in the Au-NYCTO/PVDF composites was contributed by the interfacial polarization effect and a high permittivity of the NYCTO ceramic filler. Au nanoparticles can produce the local electric field in the composites, making the dipole moments in the ß-PVDF phase and NYCTO particles align with the direction of the electric field.