Polymer films composed of polypropylene (PP) and poly(vinylidene fluoride) (PVDF) have been fabricated by extrusion with filming system. Owing to the low content of crystallites and the lubricant of carbon black, the commercial product PVDF 370 can be compatible with PP by simply blending at the molten state and the obtained film has improved dielectric constant (ɛ′ = 4.5) and reduced dielectric loss (tan δ = 0.5%) at 1000 Hz. The modified dielectric properties result from the high dielectric constant of PVDF and low dielectric loss of PP. In addition, by introducing the third polymer, low-density polyethylene (LDPE), the dielectric constant of the ternary blends (PP/PVDF 370/LDPE) can further be increased.

It's significantly urgent to develop the polymer film capacitor with large energy density and high charge-discharge efficiency for the applications of portable electronics and power hybrid system. In this study, poly(vinylidene fluoride) (PVDF) nanocomposite film incorporated with tetradecylphosphonic acid modified BaTiO₃ was prepared via solution casting to achieve high dielectric property and large energy density. The strong interactions were formed between modifier and polymer segments, which was characterised by X-ray absorption near edge structure of synchrotron radiation. The decrease of activation energy indicates that the functionalisation of BaTiO₃ weakens the heterogeneous nucleation of nanoparticle. The dielectric constant of 30 vol.% nanocomposite film achieves 50.1 with low loss of 0.02 at 100 Hz, which is attributed to the strong interaction between the phosphonic acid and fluoride atoms of PVDF segments. The energy density of 20 vol.% nanocomposite is 4.4 J/cm³ with charge-discharge efficiency of 78% at 120 MV/m due to the large interfacial polarisation. The functionalisation strategy of high-k nanofillers enhances the compatibility in polymer nanocomposite, which contributes to the flexible polymer capacitor with large energy density and high charge-discharge efficiency.

Complex perovskite microwave dielectric ceramics (MWDCs) of -type (A = Ba, Sr,…; B′ = Mg, Zn,…; B″ = Nb, Ta), which exhibit excellent dielectric properties, have currently been widely used in microwave and millimetre wave devices. Vibrational spectra, including both Raman and far-infrared (FIR) spectra, are powerful tools to investigate the atomic thermal vibrational properties of MWDCs and reveal the intrinsic origin of dielectric properties. In this review, lattice dynamics and phonon characteristics of the -type MWDCs are summarised and presented in detail to introduce remarkable progress in this field and make a guide for the design of novel advanced MWDCs. The atomic sites and the corresponding modes in Raman and FIR spectra are identified and illuminated. The effects of the processing conditions and the ordered superstructures in the nanoscale region on vibrational modes are summarised systemically. Intrinsic properties can be extrapolated from the fitting results of FIR spectroscopy, which were also discussed based on the Kramers–Krönig relations, Lorentz three-parameter classical model and four-parameter semi-quantum model. The correlations between vibrational modes (phonons), crystal structures, and dielectric properties are created, which can help to build the mathematical models so as to understand the structure–property relationship of MWDCs better.