Enhanced Dielectric Properties of LaNiO₃/BaTiO₃/PVDF: A Three-Phase Percolative Polymer Nanocrystal Composite

Abstract

Polymer (poly(vinylidene fluoride) (PVDF)) nanocrystal composites based on lanthanum nickelate (percolative oxide) and barium titanate were fabricated to obtain material systems with a high dielectric constant and low loss to be used for high-charge-storage applications. Lanthanum nickelate (LaNiO) nanocrystallites were synthesized from a simple citrate-assisted sol-gel route that yielded agglomerated crystallites of an average size of 120 nm. The defective nature of the lanthanum nickelate nanocrystals was revealed by the transmission electron microscopy studies. Hot-pressing method was executed to fabricate the LaNiO/PVDF nanocrystal composites, and their dielectric characteristics showed a low percolation threshold in the region of f (volume fraction of lanthanum nickelate) = 0.10. The percolative conductive filler-polymer nanocrystal composite at the percolation threshold exhibited a dielectric constant (ε) and loss ( D) of 55 and 0.263, respectively, at 10 kHz; the dielectric constant obtained was more than 5 times that of host matrix PVDF. To further improve upon the obtained dielectric properties from the two-phase composites, a high-dielectric-constant material, barium titanate (BaTiO) nanocrystals, with an average size of 100 nm, was embedded in the polymer matrix as the third phase. The dielectric properties of the three-phase nanocrystal composites were measured as a function of the volume fraction of lanthanum nickelate (which was limited within the percolation threshold), and a dielectric constant as high as 90 and the associated loss of 0.13 at 10 kHz were achieved from f = 0.09 and f = 0.20. The obtained dielectric constant from this system is 9 times more than that of PVDF and 3 times that of a two-phase barium titanate/PVDF composite, which proves to be a promising material for charge-storage applications.

Enhancing High-Frequency Dielectric Properties of Beta-SiC Filled Nanocomposites from Synergy between Percolation and Polarization

“…When a fine linear fitting (adjusted R 2 of the fitting was 0.99) was made onto the data in Figure 4 b, the u value could be achieved as 1.02 for the sample. As expected, this u value (1.02) was much higher than the universal u value (0.70) [ 48 ] predicted by percolation theory. The gap between the two u values was calculated to be 0.32, which may be attributed to the contribution of induced polarization to the ac conductivity of this sample.…”

“…As the volume concentration of conducting filler is near the percolation threshold, the ac conductivity ( σ ) of composite has much to do with the angular frequency ( ω ) of the applied ac electric field ( ω = 2π f , f is measuring frequency). The relation has been expressed as ‘ σ ∝ ω u ’ ( u is the critical exponent) [ 48 ]. In Figure 4 b, the relation between log( σ ) and log( ω ) for the SiC-0.29/PVA sample was obtained, based on the known data in Figure 4 a.…”

Significant enhancement of dielectric permittivity and percolation behaviour of La2−xSrxNiO4/poly(vinylidene fluoride) composites with different Sr doping concentrations

“…This clearly indicated that the effect of interfacial polarisation on the enhanced 3 0 values was dominant, especially for the LSNO-2/PVDF composite, as a result of their percolative nature. Such a drastic increase in the 3 0 value for the LSNO-2/PVDF composite could also be rationalised by the micro-capacitor model, 33,42 which considers the consistency of a network of several micro-capacitors formed by a thin layer of PVDF polymer between two neighbouring LSNO-2 particles, where each of these micro-capacitors contributes to an abnormally high capacitance. Fig.…”

Optimizing Strategy for the Dielectric Performance of Topological-structured Polymer Nanocomposites by Rationally Tailoring the Spatial Distribution of Nanofillers

“…Hu et al designed the polypropylene composites co-filled with semi-conductive tetra-needle-shaped zinc oxide whiskers (ZnO) and barium titanate (BT) nanoparticles, 37 where an improvement of dielectric permittivity (from 8.5 to 11) and a decline of loss tangent (from 0.008 to 0.004) could be realized simultaneously. Jaschin et al constructed a ternary percolative polymer composite consisting of lanthanum nickelate (LaNiO3) nanocrystals, barium titanate (BaTiO3) nanocrystals and polyvinylidene fluoride, 38 a high dielectric constant of 90 at 10 kHz (and a low loss of 0.13) was obtained with the LaNiO3 content below the percolation threshold. The achieved dielectric constant is around 9 times that of pure PVDF and 3 times that of BaTiO3/PVDF nanocomposite.…”