Greatly enhanced dielectric permittivity in La_1.7Sr_0.3NiO₄/poly(vinylidene fluoride) nanocomposites that retained a low loss tangent

摘要

The effect of La_1.7Sr_0.3NiO₄ nanoparticles (LSNO-NPs) on the dielectric properties of LSNO-NPs/polyvinylidene fluoride (LSNO-NPs/PVDF) composites is presented. LSNO-NPs/PVDF composites fabricated via a liquid-phase assisted dispersion and hot-pressing methods showed a homogeneous dispersion of LSNO-NPs in a PVDF polymer matrix. The dielectric permittivity (ε′) continuously increased with increasing volume fraction of LSNO-NPs from f_LSNO = 0–0.20, following the effective medium theory and Lichtenecker's logarithmic models. This result was intrinsically caused by a very large ε′ ≈ 105 of LSNO-NPs ceramic particles. At f_LSNO = 0.25, ε′ deviated from the conventional mixed models, indicating a dominant extrinsic effect. A rapid change in ε′ of LSNO-NPs/PVDF composites was observed when f_LSNO > 0.3. A largely enhanced dielectric response with ε′ ≈ 3285 at 1 kHz was obtained at f_LSNO = 0.35, while the loss tangent was still low (≈0.83). This extremely enhanced ε′ value is attributed to the large interfacial areas and very short interparticle distances between LSNO-NPs (≈20–30 nm) separated by a thin layer of PVDF, forming highly effective microcapacitors. The overall ε′ values are well described by the combination model of effective medium percolation theory.