BaTiO₃ (BT) nanoparticles treated in H₂ and then coated with a layer of SiO₂ were used as the starting material to synthesise BT–SiO₂ nanocomposites through the conventional ceramic process. A denser morphology was obtained in the BT–SiO₂ composites. The H₂ treatment induced not only the oxygen vacancies, but also other changes (i.e. ionic disorders) in the BT. These ionic disorders were more permanent and enhanced the reaction between the BT and SiO₂ during the sintering process. Comparing with the nanocomposites sintered from the untreated BT nanoparticles, the nanocomposites sintered from the H₂ treated BT nanoparticles exhibit an enhanced dielectric performance (i.e. a higher dielectric constant and a high electric breakdown field). Among the temperatures (i.e. 850, 900, 950 and 1000°C) used to treat the BT nanoparticles in H₂, it is experimentally found that 950°C is the best. For example, for the composites with 20 wt% SiO₂, the dielectric constant is enhanced more than four times and the breakdown field is enhanced by about 30%. It is believed that the enhancement in the dielectric response is due to the dipoles formed by the ionic disorders, especially the acceptor defects.

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.

Perovskite dielectric oxide thin films are tremendously important because of their promising applications in microelectronics and optic-electronic devices. Towards scalable applications of these materials, the development of well-controlled and cost-effective fabrication techniques is still under development. Here, recent progresses in the fabrication of perovskite dielectric oxide thin films by using a generic chemical solution deposition technique named polymer-assisted deposition (PAD) are reviewed. In this technique, metal ions are bonded to water-soluble polymers, forming stable and homogeneous precursor solutions of metallic ions surrounded by polymers which prevent hydrolysis of metal ions. Fabrication of the perovskite dielectric oxide thin films using the PAD technique, both on single crystal substrates and base metallic substrates, has been realised with good controllability. The qualities of the films are comparable with those of the ones prepared by physical-vapour deposition techniques.

Since the proposal of the notion of nanodielectric, the space charge characteristics of nanodielectrics have been widely investigated. With the addition of nanoparticles, some nanodielectrics exhibit smaller space charge accumulation amount during the polarisation, and also faster charge decay during the depolarisation, which is believed to be related to the interfacial layer between the nanoparticle and the base material. In this study, the space charge measurement methods, theoretical models, and experimental results are reviewed in detail. Space charge measurement methods have been greatly improved after more than 20 years development. The nature of the interfacial layer between the nanoparticle and the base material has been investigated in detail, and based on that, several models are proposed to explain some electrical experimental results of nanodielectrics. Furthermore, the parameters of nanoparticle (such as the type, size, amount, shape, and the surface modification), the experimental conditions, and the base material properties can strongly affect the space charge characteristics of nanodielectrics. This study will provide useful research results and conclusions for researchers, and may also be an overview for recent study and an outlook for future investigation on space charge characteristics of nanodielectrics.

The composites reported here were prepared through a melt-rolling mixing process, in which surface passivated multi-wall carbon nanotube and poly(vinylidene fluoride) were used as the filler and the matrix, respectively. X-ray diffraction, precision inductance–capacitance–resistance, and laser flash thermal-diffusivity analyses were employed to characterise the structural, electrical and thermal properties. Results indicate that through the surface passivation of carbon nanotubes, the electrical resistivities of the composites were greatly enhanced, while the thermal conductivities do not change significantly. The electrical properties were discussed in comparison with the Maxwell–Wagner polarisation, universal law, and Gerhardt's method.