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In this work, (1 − x)(0.94Na0.5Bi0.5TiO3–0.06BaTiO3)–xKTaO3 (x = 0–0.30) ceramics are developed for dielectric capacitor applications. The introduction of KTaO3 from x = 0 to 0.30 increases the tolerance factor t from 0.984 to 1.005 and causes the decrease of ferroelectric rhombohedral phase in the ceramics. Besides, a gradual structural change toward a higher symmetry can be detected, accompanied by the obvious domain refinement. In the aspect of electrical property, the strengthened dielectric relaxation leads to the greatly enhanced thermal stability of dielectric response. The decline in Ts from 98 to −96°C causes a significant widening of the low‐temperature region with temperature‐stable dielectric constant εr and low dielectric loss tan δ. The x = 0.30 ceramic shows a high εr (25°C) of 1094 with the temperature coefficient of capacitance ≤±15% over −70 to 200°C, which exceeds the X9R standard. Meanwhile, tan δ is less than 0.02 in a wide temperature range of −35 to 300°C. In addition, the ultrafine grain size of 290 nm, large bandgap of 3.22 eV, and high resistance of the x = 0.30 ceramic contribute to its electrical breakdown strength. A linear‐like P–E loop with the large discharged energy density WD ∼ 3.50 J/cm3 and high energy efficiency η ∼ 90.1% is obtained under 28 kV/mm at room temperature. The thermal stability of the energy storage performance is also satisfactory with the variation of WD less than 15% over −40 to 200°C, and the η is higher than 85%. [ABSTRACT FROM AUTHOR]

Polymer dielectrics are attracting increasing attention for electrical energy storage owing to their advantages of mechanical flexibility, corrosion resistance, facile processability, light weight, great reliability, and high operating voltages. However, the dielectric constants of most dielectric polymers are less than 10, which results in low energy densities and limits their applications in electrostatic capacitors for advanced electronics and electrical power systems. Therefore, intensive efforts have been placed on the development of high‐energy‐density polymer dielectrics. In this perspective, the most recent results on the all‐organic polymer dielectrics are summarized, including molecular structure design, polymer blends, and layered structured polymers. The challenges in the field and suggestions for future research on high‐energy‐density polymer dielectrics are also presented. [ABSTRACT FROM AUTHOR]

Dielectric composites based on ferroelectric ceramics nanofibers are attracting increasing attention in capacitor application. In this work, the sol–gel method and electrospinning technology are utilized to prepare one-dimensional Na0.5Bi0.5TiO3 (NBT) nanofibers, and the influence of electrospinning process parameters such as spinning voltage, liquid supply rate, and collector speed on the morphology and structure of nanofibers are systematically explored. The final optimized parameters include the applied voltage of 20 kV, the solution flow rate of 1 mL/h, and the collector's rotation speed of 1500 rpm. The optimized NBT nanofibers are introduced into the PVDF polymer matrix for energy storage application. Owing to the enhanced interfacial polarization between PVDF matrix and NBT nanofibers with a high aspect ratio, the NBT–PVDF nanocomposites achieve a high discharge energy density of 14.59 J cm−3 and an energy efficiency of 53.69% at 490 kV mm−1, which are higher than those of pure PVDF, i.e., 10.26 J cm−3 and 48.17% at 420 kV mm−1, respectively. The results demonstrate that the strategy of synthesizing NBT nanofibers using the electrospinning method is of great potential for high-performance dielectric capacitor application. [ABSTRACT FROM AUTHOR]

Electric‐field‐induced phase transitions in Bi0.5Na0.5TiO3‐based relaxor ferroelectrics are essential to the control of their electrical properties and consequently in revolutionizing their dielectric and piezoelectric applications. However, fundamental understanding of these transitions is a long‐standing challenge due to their complex crystal structures. Given the structural inhomogeneity at the nanoscale or sub‐nanoscale in these materials, dielectric response characterization based on terahertz (THz) electromagnetic‐probe beam fields is intrinsically coordinated to lattice dynamics during DC‐biased poling cycles. The complex permittivity reveals the field‐induced phase transitions to be irreversible. This profoundly counters the claim of reversibility, the conventional support for which is based upon the peak that is manifest in each of four quadrants of the current–field curves. The mechanism of this irreversibility is solely attributed to polar clusters in the transformed lattices. These represent an extrinsic factor, which is quiescent in the THz spectral domain. [ABSTRACT FROM AUTHOR]

A novel percolative nanocomposite with super‐high permittivity and supressed dielectric loss is achieved, which is due to the hierarchical interfaces induced by BaSrTiO3 nanocuboid dotted graphene sheets and further modification of dapamine. [ABSTRACT FROM AUTHOR]

Microstructure, dielectric properties, and ferroelectric relaxor behavior of Ca doped barium strontium titanate (BSCT) ceramics prepared by solid-state reaction were investigated. It was demonstrated that the unit cell volume of the BSCT ceramics firstly decreases with the increase of Ca contents up to x = 0.08, but increases with further addition of Ca ( x ≥ 0.12). The shrinkage of the unit cell volume resulted from the substitution of Ba by Ca when x ≤ 0.08, which enhanced the relaxor behavior of the ferroelectrics. Conversely, a small amount of Ca substituted for Ti site when x ≥ 0.12, which weakens the relaxor behavior of the BSCT ceramics. The 8 mol % doped BSCT ceramic yielded the maximum index of relaxation ( γ) of 1.90 and made it a promising candidate for future industrial application of efficient and eco-friendly relaxor ferroelectric materials. [ABSTRACT FROM AUTHOR]

Abstract: Commercial glass frits (lead borosilicate glasses) were employed as the sintering aids to reduce the sintering temperatures of BST ceramics. The effects of the glass content and the sintering temperature on the microstructures, dielectric properties and tunabilities of BST ceramics have been investigated. Densification of BST ceramics of 5wt% glass content becomes significant from sintering temperature of 1000°C. The glass content shows a strong influence on the Curie temperature T c, permittivity and the diffuse transition. X-ray results show all BST ceramics exhibit a perovskite structure and also the formation of a secondary phase, Ba2TiSi2O8. The shift of BST diffraction peaks towards higher angle with increasing the glass content indicates the substitution of Pb2+ in Ba2+ site, which mainly accounts for the diffuse transition observed in these BST ceramics. BST ceramics with 10wt% glass additives possess the highest tunability at all four sintering temperatures. A tunability of 12.2% at a bias field of 1kV/mm was achieved for BST ceramics with 10wt% glass content sintered at 900°C. [Copyright &y& Elsevier]

There is still a problem of low energy storage density in dielectric capacitors which is a core component of power systems. For the improvement of the energy storage density, the linear dielectric material CaTiO 3 (CT) was introduced in Na 0.5 Bi 0.5 TiO 3 (NBT) ceramics in this paper. By modifying the A site, a new relaxor ferroelectric ceramic was successfully synthesized and attained a recoverable density (W rec) of 2.34 J/cm3 at x = 0.18. Moreover, the preparation process was optimized in this paper. Through the viscous polymer process (VPP) route, the energy density (W A) of 82NBT-18CT VPP ceramic further reaches 6.45 J/cm3 at 340 kV/cm, with efficiency (η) up to 75% and a W rec of 4.82 J/cm3. At the same time, the change of W rec is small at temperature (30–150 °C) and frequency (1 Hz–300 Hz), which demonstrates its excellent stability. The discharge power density reaches about 180 MW/cm3 and the discharge time is 0.117 μs, which indicates its excellent pulse discharge performance. The results show that 82NBT-18CT lead-free relaxation ferroelectric material is expected to become ideal for high-energy storage applications. [ABSTRACT FROM AUTHOR]

• The density and depth of traps are improved attributed to the incorporation of F4-TCNQ with high electron affinity. • Physical interaction between F4-TCNQ and PEI endows composites with dense chain packing and increased Young's modulus. • At 150 °C, a high discharged energy density of 7.84 J/cm3 is achieved under 670 kV/mm. High temperature resistance is essential for electrostatic capacitors, for example, the operating temperature of capacitors used in inverters for hybrid electric vehicles is around 140–150 °C. However, the reliability of current commercial dielectrics, such as biaxial stretched polypropylene (BOPP), significantly degrades when the operating temperature exceeds 105 °C. In this work, an all-organic dielectric utilizing two mechanisms—high electron affinity and physical interaction—is designed to enhance the capacitive performance. Specifically, the molecular semiconductor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), with ultra-high electron affinity (5.24 eV) and peripheral electronegativity, is incorporated with polyetherimide (PEI). Deep electron traps are successfully constructed to capture free electrons due to the incorporation of high-electron-affinity F4-TCNQ. Moreover, it is difficult for the captured electrons to escape because of the Coulomb force between electrons in the low unoccupied molecular orbital (LUMO) of F4-TCNQ and holes in the highest occupied molecular orbital (HOMO) of PEI. From another point of view, physical interaction is formed between the peripherally electronegative groups of F4-TCNQ and the positively charged phenyls of PEI, improving the packing density among polymer chains and the Young's modulus. Consequently, the electromechanical breakdown strength is enhanced. These two mechanisms play their part simultaneously, realizing significantly suppressed conductivity loss and increased breakdown electric field. Accompanied by an improved dielectric constant, the discharged energy density of F4-TCNQ/PEI composites is significantly increased over a wide temperature range. Especially at 150 °C, the discharged energy density (U e) of 0.6 wt% F4-TCNQ/PEI reaches 7.84 J/cm3 at 670 kV/mm, which is 123 % higher than that of PEI (3.52 J/cm3). The U e is still as high as 5.12 J/cm3 even when the discharged efficiency (η) is over 90 %. This work exhibits a promising prospect of all-organic dielectrics in capacitive application at high temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • 0–3 type composite structure is achieved in the BNT-SBT-ZnO ceramics. • ZnO not only acts as a sintering aid, but also enhances the random fields and polar nanoregions activity by Zn2+ doping. • Obvious element segregation is generated in the BNT-based matrix grains showing different Sr2+/(Bi3+, Na+) ratios. • Optimized energy storage performance is realized with W rec ∼ 5.84 J/cm3, η ∼ 93 %, and E B ∼ 40 kV/mm. In this work, ZnO is introduced into the 0.55Bi 0.5 Na 0.5 TiO 3 -0.45Sr 0.7 Bi 0.2 □ 0.1 TiO 3 (BNT-SBT) to optimize the dielectric energy storage performance. ZnO is not only used as a sintering aid to decrease the sintering temperature and ceramic grain size, but also enhances the random fields and polar nanoregions activity in the ceramics by Zn2+ doping. Intriguingly, the ZnO-modified BNT-SBT ceramics present a 0–3 type composite structure containing the TiZn 2 O 4 and Bi 2 Ti 2 O 7 linear dielectrics. Moreover, obvious element segregation is generated in the BNT-based matrix grains showing different Sr2+/(Bi3+, Na+) ratios and polarization magnitudes. The significant variations in composition distribution, grain and domain configurations cause the overall optimization of energy storage properties, reflected in the enhanced breakdown strength, delayed polarization saturation, and reduced polarization hysteresis. As a result, the optimized W rec ∼ 5.84 J/cm3 and η ∼ 93 % at 40 kV/mm is obtained in the BNT-SBT-0.10ZnO ceramic, superior to that of the BNT-SBT ceramic (W rec ∼ 3.35 J/cm3 and η ∼ 89 % at 28 kV/mm). [ABSTRACT FROM AUTHOR]

Dielectric capacitors are of urgently demand in modern micro-electric industry. The surface modified inorganic filler introduced to polymer matrix represents a promising avenue for the dielectric material's enhancement of energy storage density. To ease the electric field concentration of the composite induced by permittivity difference between ceramic fillers and polymer matrix, the specific dielectric fillers of TiO 2 nanowires modified BT particles were synthesized in this study. Gradient dielectric composite consisting of poly(vinylidene fluoride-co-hexafluoropylene) [P(VDF-HFP)] matrix ( ε r ∼10), TiO 2 shell ( ε r ∼40), and BaTiO 3 (BT) core ( ε r ∼1000) were focused to investigate the electric field contribution and interface polarization. The results revealed that the permittivity of the composites increased as a result of large interfacial polarization induced by the large specific surface area of the nanowires as compared to the composite with randomly mixed TiO 2 /BT fillers. The breakdown strength of the composite was slightly improved with 20 vol% fillers, attributed to the fact that the electric field intensification was weakened by the BT@TiO 2 /Dop gradient dielectric fillers. The composite could endure up to 10 6 times of field cycling at the applied cycling field and the leakage current density was rather low. The composites with 20 vol% fillers exhibited a discharged energy density of 2.8 J/cm 3 at a low electric field, which was much higher than that of the neat P(VDF-HFP). The findings of this research introduced a new inorganic particle with large specific surface area and gradient dielectric permittivity as filler in composite for energy storage application. [ABSTRACT FROM AUTHOR]

[Display omitted] • High performance nitrated polystyrene can be prepared on a large scale. • Nitrated polystyrene shows high permittivity and high breakdown strength. • The mechanism of polarization and breakdown was investigated. • The discharge energy density of 6.32 J cm−3 was achieved in nitrated polystyrene. It is a great challenge to achieve ultrahigh discharge energy density (U e) via improving simultaneously permittivity and breakdown strength of polymer dielectrics. In this work, it is first found that nitrated polystyrene films possess excellent dielectric and energy storage properties. The mechanism for the permittivity and breakdown strength of nitrated polystyrene were investigated. On one hand, substituent group of dipolar nitro can increase the glass transition temperature and permittivity of polystyrene. On the other hand, nitro substituent group can not only construct charge traps to reduce the carrier mobility under high fields, but also effectively destroy the carrier channel formed by the accumulation of pi-pi between the benzene rings under high field, both which favor the enhancive breakdown strength of polystyrene. As a results, the maximum U e of 6.32 J cm−3 at 640 MV m−1 was obtained in nitrated polystyrene with a substitution degree of 15%, which is 2.38 times than that of neat polystyrene. Furthermore, at 200 MV m−1 and 100 °C, nitrated polystyrene with a substitution degree of 66% produced U e of 1.1 J cm−3 with 88% efficiency. This study demonstrates that the nitration can significantly promote permittivity and breakdown strength of polystyrene, and provides a guidance for preparing high-performance and large-scale polymer dielectrics. [ABSTRACT FROM AUTHOR]

In this work, polyimide-based (PI) nanocomposites containing two-dimensional oxidized MXenes as filler exhibit obviously enhanced capacitive performances at elevated temperature. To decrease the aggregation, Ti 3 C 2 T X colloidal solution was directly introduced into PI matrix via in-situ polymerization method. Because of the strong electrostatic attraction to electrons, the charge can be captured by oxidized MXenes, resulting in suppressed leakage current and greatly improved breakdown strength. Therefore, the largest discharged energy density (U d) of 8.67 J/cm3 and the efficiency of 84.1% are achieved at 648 kV/mm in 0.5-wt% oxidized MXenes/PI nanocomposites at room temperature, which is more than twice than that of pure PI. In high temperature, significantly increased U d of 5.46 J/cm3 at 100 °C and U d of 2.05 J/cm3 at 150 °C are obtained compared with the pure PI (1.28 J/cm3@100 °C). This research contributes to broadening the application of oxidized MXene in flexible dielectrics and providing an effective way for the preparation of high-performance dielectric polymer-based composites over a broad temperature range. [Display omitted] • The oxidized Ti 3 C 2 T x is proposed to construct polyimide-based dielectric composites. • The oxidized MXenes can capture charges to improve breakdown strength. • The superior discharge energy density is achieved at elevated temperature. [ABSTRACT FROM AUTHOR]

There has been recently a great progress in the development of dielectric capacitors for high temperature electronic applications. The design of lead-free ceramics with high dielectric permittivity, low dielectric loss and a limited variation of these parameters over a wide temperature range is still a big challenge. In this work, lead-free Bi 0.35 Na 0.65 – 0.5x Rb 0.5x Ti 0.7 Nb 0.3 O 3 (x = 0–0.05) bulk ceramics were prepared using the solid-state reaction method. Upon Rb substitution, the variation of the dielectric permittivity was reduced substantially, in particular, at high temperature (over 200 °C). In addition, a low temperature coefficient of capacitance (TCC ≤ 10%) together with an ultra-low dielectric loss (tan δ ≤ 0.05) were achieved for the Bi 0.35 Na 0.63 Rb 0.02 Ti 0.7 Nb 0.3 O 3 sample in the temperature range from −43 °C to 292 °C. The new relaxor-type ferroelectrics also possess the outstanding stability of the dielectric properties under high DC bias voltage, which makes them promising materials for high-performance capacitors of the next generation. Unlabelled Image • Rb/Nb co-substituted Bi 0.5 Na 0.5 TiO 3 –based ceramics display TCC < 10% in the temperature range of −43 °C–292 °C. • The BNT-derived relaxors exhibit high permittivity (>800) and ultra-low dielectric loss (≤0.05) from −43 °C up to 292 °C. • The variance of the capacitance of the Bi 0.5 Na 0.5 TiO 3 –based ceramics is lower than 150 ppm under the DC voltage of 1 kV. [ABSTRACT FROM AUTHOR]

• Low-cost natural-sepiolite was used to develop large-scale production of high performance dielectrics. • Organophilic-sepiolites nanofibers possessed well dispersion in the PVDF matrix. • The maximal U e of 7.2 J·cm−3 was achieved in 2.5%-APTES@Sepiolites/PVDF nanocomposites. The preparation of large-aspect-ratio nanofillers is challenging due to the complicated and expensive artificial processing procedures and low yields, obstructing scale-up production of 1D nanofillers/polymer dielectric nanocomposites. In this paper, a kind of natural sepiolite nanofiber was utilized to fabricate scale-up of PVDF-based dielectric nanocomposites. The sepiolite nanofibers were modified by aminopropyltriethoxysilane (denoted as APTES@Sep) and 1H,1H,2H,2H-perfluoroheptadecane trimethysiloxane (denoted as PFDTES@Sep), respectively, before being incorporated into PVDF. The effect of nanfibers loading and modifiers on the dielectric behaivor and energy stroage properties of nanocomposites was investigated. As results, the nanocomposites with 7.5 vol% PFDTES@Sep exhibited highest permittivity of 16.4 at 103 Hz originating from well dispersibility, strong interfacial polarization and orientation polarization. The nanocomposites with 2.5 vol% APTES@Sep displayed maximal discharged energy density of 7.2 J·cm−3 owing to highest breakdown strength. This work provides a simple and cheap strategy for developing high performance flexible dielectric nanocomposites, which is suitable for large-scale preparation. [ABSTRACT FROM AUTHOR]