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Due to high power density, fast charge/discharge speed, and high reliability, dielectric capacitors are widely used in pulsed power systems and power electronic systems. However, compared with other energy storage devices such as batteries and supercapacitors, the energy storage density of dielectric capacitors is low, which results in the huge system volume when applied in pulse systems. Therefore, to meet the needs of device miniaturization and integration, reducing the system volume and increasing the energy storage density have become very key research hot spots in the dielectric energy storage fields. In this paper, we first introduce the research background of dielectric energy storage capacitors and the evaluation parameters of energy storage performance. Then, the research status of ceramics, thin films, organic polymers, and organic–inorganic nanocomposites for energy storage is summarized. Next, the methods of improving the energy storage density of dielectric capacitors are concluded. For ceramic blocks and films, methods, such as element doping, multi-phase solid solution/coexistence structure, "core–shell" structure/laminated structure, and other interface adjustments, are effective to increase the energy storage density. While for organic–inorganic nanocomposites, the energy storage performance can be optimized by the surface modification and distribution of fillers, and multi-layer structure design. Finally, the future development tendency of the energy storage materials is prospected to consolidate the research foundation of dielectric energy storage and provide certain guidance value for their practical applications. [ABSTRACT FROM AUTHOR]

The equivalent and aliovalent ions (Zr, Al and Nb) doped BaBiTiO ceramics were prepared by a solid-state reaction method. X-ray diffraction patterns showed that the ceramics have a tetragonal structure with space group of I4/ mmm at room temperature. The plate-like morphology was observed by scanning electron microscope (SEM) and the anisotropy of grains weakens after doping. The dielectric properties and complex impedance spectra of all samples were studied. The results showed that the dielectric properties demonstrate strong dependence on the type of doping element. Al doping decreases the dielectric constant for limiting the vibration space of Ti ions in small cell volume. Nb doping as a donor induces the formation of Ti and the increase of dielectric constant and loss; simultaneously, it decreases the temperature of dielectric constant maximum obviously and the temperature stability of dielectric constant. Doping leads to the increase of diffuseness of phase transition, due to the increasing distribution disorder of cations. Through Arrhenius fitting, the activation energy was estimated to be 0.81-1.18 eV, which could be attributed to the thermal motion of oxygen vacancy and grain distortion. [ABSTRACT FROM AUTHOR]

Fe-doped SiC nanowires samples were fabricated using high-purity carbon nanotubes, SiO and Fe powders as starting materials. The surface morphology, microstructure and chemical composition of the samples were investigated by field emission scanning electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The results reveal that the samples crystallize with cubic structure and grow along the [111] direction. Results of magnetic measurement show the samples exhibit room temperature ferromagnetism without the formation of magnetic clusters. The saturation magnetization of the samples decreases with the increase of Fe concentration. From the first-principles calculations, it is strongly proposed that the magnetic state are depend on the distance between Fe dopant atoms. Combined the theoretical calculations with the experimental results, it is suggested that C vacancies play a vital role in determining the magnetic properties in Fe-doped SiC nanowires. [ABSTRACT FROM AUTHOR]

Abstract: (002)-Preferred orientation ZnO and Li-doped ZnO thin films on glass substrates and Li-doped ZnO/ZnO bilayers on fluorine-doped SnO2 glass substrates are grown by pulsed laser deposition technique. These films are characterized by X-ray diffraction, UV–visible transmission spectroscopy, surface photovoltage spectroscopy, and electric measurements. The optical transmittance of Li-doped ZnO/ZnO bilayers is about 86%. The bilayer grown on FTO glass substrates exhibits a typical rectifying characteristic of p–n heterojunctions. In addition, the photovoltaic response of ZnO is blue-shifted from 380 to 363nm and greatly enhanced resulting from the formation of p–n homojunctions based on ZnO. [Copyright &y& Elsevier]

Sm and Ti co-doped BiFeO 3 (BFO) ceramics with Fe vacancies—Bi 0.86 Sm 0.14 FeO 3 , Bi 0.86 Sm 0.14 Fe 0.99 Ti 0.01 O 3 , and Bi 0.86 Sm 0.14 Fe 0.9 Ti 0.05 O 3 —were prepared by a solid-state method using a rapid liquid process. X-ray diffraction indicated that all samples exhibited a rhombohedral structure with a minor secondary phase. The structural transformation from a rhombohedral (space group: R 3 c ) to orthorhombic structure (space group: Pnma ) was observed in the sample of Bi 0.86 Sm 0.14 Fe 0.9 Ti 0.05 O 3 , which was also confirmed by Raman scattering spectra. Microstructural investigations with scanning electron microscopy showed a reduction in grain size with doping of BFO. The dielectric loss of Bi 0.86 Sm 0.14 Fe 0.9 Ti 0.05 O 3 reaches 0.05 (at 100 Hz) owing to the introduction of Ti and Fe vacancies. Ferroelectromagnetic measurements revealed the existence of ferroelectricity with a remanent polarization of 0.24 µC/cm 2 in Bi 0.86 Sm 0.14 FeO 3 , paraelectricity in Bi 0.86 Sm 0.14 Fe 0.9 Ti 0.05 O 3 , and weak ferromagnetism with a remanent magnetization of 0.2 emu/g in Bi 0.86 Sm 0.14 Fe 0.99 Ti 0.01 O 3 . The two composition-driven phases exist simultaneously and the different coercive field might be related to the jumps in the ferromagnetic hysteresis loops. Both the ferroelectric and magnetic properties were shown to correlate with the composition-driven structural evolution. [ABSTRACT FROM AUTHOR]

Fe-doped BaTiO 3 films were prepared on quartz substrates by sol-gel route. Linearly optical constants of the films were obtained by fitting transmittance spectra with Adachi’s model. With increasing Fe composition, refractive index n at 532 nm increases, single oscillator energy E c and dispersion energy E d increase, but optical band gap E g decreases from 3.78 to 3.63 eV. In addition, nonlinear optical properties of the Fe-doped BaTiO 3 films were analyzed by Z-scan method. Nonlinear optical responses of the BaTiO 3 films were enhanced by Fe doping. For BaTi 0.96 Fe 0.04 O 3 film, the third-order nonlinear refractive index coefficient γ , the nonlinear refractive index coefficient n 2 , the nonlinear absorption coefficient β and the third-order nonlinear susceptibility χ (3) are 1.98 × 10 −13 m 2 /W, 1.03 × 10 −6 esu, 1.33 × 10 −7 m/W, 2.38 × 10 −7 esu respectively. The nonlinearity is predominated by the nonlinear refractive behavior. These results suggest that Fe doping may tune the linear and nonlinear optical properties of BaTiO 3 films, which indicates that Fe-doped BaTiO 3 films are promising materials for applications in optical devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] (F, Y)-codoped TiO2 nanoparticles were prepared by a simple sol–gel method. [•] The highest photocatalytic activity (15 times of that over the pure TiO2) was exhibited in the codoped TiO2 with 0.05% Y doping level. [•] The Y doping induced oxygen vancancies played a duel role on the photocatalyic activity of the codoped TiO2. [•] The photocatalytic reactive oxygen species are critical to the photocatalytic degradation processes. [Copyright &y& Elsevier]