Flexible La1.5Sr0.5NiO4/Poly(vinylidene fluoride) composites with an ultra high dielectric constant: A comparative study

Poly(vinylidene fluoride) (PVDF)-based polymer composites filled with high-permittivity La1.5Sr0.5NiO4 (LSNO) particles have been fabricated to produce a composite material with excellent dielectric performance and good mechanical flexibility. Micro-sized (mu LSNO) and nano-sized LSNO (nLSNO) particles are used separately as fillers. The dielectric properties of the composites are determined by their particle sizes, resultant interfacial area, and the interparticle distances between the LSNO particles. The percolation threshold of the nLSNO/PVDF composite is lower than that of the mu LSNO/PVDF composite. A greatly enhanced dielectric response with a high epsilon' approximate to 565.9 at 1 kHz and room temperature and an effectively suppressed low loss tangent (tan delta approximate to 0.28) are obtained in the nLSNO/PVDF composite with a filler volume fraction of 30 vol %. The greatly enhanced epsilon' value of nLSNO/PVDF can be explained by a combination of the interfacial polarization at the semiconducting nLSNO-insulating PVDF interfaces, an intrinsically giant epsilon' response in nLSNO particles, and shorter interparticle distances between nLSNO particles in the PVDF matrix, while the retained low tans value is primarily attributed to the formation of a micro-capacitor microstructure.