Search

As microelectronic devices move toward integration and miniaturization, the thin film capacitors with high energy density and charge/discharge efficiency have attracted immense interests in modern electrical energy storage systems. Despite morphotropic phase boundary (Na0.8K0.2)0.5Bi0.5TiO3-based lead-free materials with outstanding ferroelectric and piezoelectric properties, while large ferroelectric hysteresis with high remanent polarization (Pr) hinder to improve energy storage capability. Here, novel lead-free relaxor-ferroelectric (RFE) thin film capacitors with high energy density are successfully prepared in (1-x) (Na0.8K0.2)0.5Bi0.5TiO3-xBa0.3Sr0.7TiO3 [(1-x)NKBT-xBST] systems. Introducing BST into the NKBT systems is expected to reduce remanent polarization (Pr) on account of coupling reestablishment of the polar nano-regions (PNRs) and improving the relaxation behavior. As a result, 0.6NKBT-0.4BST thin film exhibits high energy density (Wrec ∼ 54.79 J/cm3) together with satisfactory efficiency (η ∼ 76.42%) at 3846 kV/cm. The stable energy storage performances are achieved within the scope of operating temperatures (20–200 °C) and fatigue cycles (1-107 cycles). This work furnishes a new technological way for the design of high energy-density thin film capacitors.

Considering the significant threat of heat to electronic equipment and the heat dissipation problems existing in powerful systems, thermal management materials are in high demand. In conjunction with the increasing desire of dissipating heat and stabilizing temperature, high thermal conductivity and phase change latent heat are attracting more attention when designing thermal management material. This work proposes a strategy to combine phase change matrix and thermally conductive filler using freeze casting. The highest thermal conductivity reaches 23.1 W m-1 K-1 accompanied by 62 J g-1 phase change latent heat. Meanwhile, replacing ice with organic phase change material in freeze casting can result in an aligned structure. This discovery will pave a novel way for introducing thermal latent heat without abandoning the aligned structure.

The need for high-performance capacitors that possess superb discharged energy density and efficiency is continually increasing. Relaxor ferroelectric 0.94(0.65Na0·5Bi0·5TiO3-0.35Sr0·7Bi0·2TiO3)-0.06K0·5Na0·5NbO3 ((NBT-SBT)-KNN) ceramics with different MnO2-doping concentrations are prepared in this study. An outstanding discharged energy density (Wrec = 3.25 J/cm3) and efficiency (η = 93.8%) are concurrently acquired under 280 kV/cm for these doped ceramics. The ceramics also exhibit extraordinary thermal (30–200 °C), frequency-dependent (1–200 Hz) and fatigue stability (104 st). Additionally, the (NBT-SBT)-KNN-0.08 mol.% MnO2 ceramic displays a large power density (42 MW/cm3) and an ultrafast discharge speed (98 ns). This contribution offers powerful support for the use of energy storage ceramics in practical applications.

Lead-free ceramic capacitors play an important role in electrical energy storage devices because of their ultrafast charge/discharge rates and high power density. However, simultaneously obtaining large energy storage capability, high efficiency and superior temperature stability has been a huge challenge for practical applications of ceramic capacitors. Here, the relaxor ferroelectric (1-x)[0.8Bi0.5Na0.5TiO3-0.2Ba(Zr0.3Ti0.7)O3]-xSr0.7La0.2TiO3 ((1-x)(BNT-BZT)-xSLT) ceramics are prepared through solid-state reaction method to obtain excellent comprehensive energy storage performances. Particularly, high recoverable energy density (Wrec ∼ 2.6 J/cm3) as well as superior efficiency (η ∼ 92.2 %) can be achieved simultaneously under 210 kV/cm with composition of x = 0.3. Meanwhile, the corresponding ceramic shows excellent temperature (20−140 °C), frequency (1−200 Hz) and cycle stabilities (106 st). Additionally, the 0.7(BNT-BZT)-0.3SLT ceramic also displays high power density (PD ∼ 38.8 MW/cm3) and extremely short discharge time (τ0.9 ∼ 0.11 μs). Therefore, this study provides a useful guideline for designing novel BNT-based ceramics with superior comprehensive energy storage performances.

Morphotropic phase (MPB) eco-friendly ferroelectric 0.94Bi0.5Na0.5TiO3- 0.06BaTiO3 (NBT-BT) ceramics exhibits superior piezoelectric performances. However, the large remnant polarization (Pr) and low breakdown strength (Eb) of NBT-BT systems hinders application in energy storage capacitors. Herein, the Bi(Zn1/3Nb2/3)O3 (BZN) is selected to partially replace the NBT-BT ceramics to break ferroelectric long-range order domains achieving higher energy storage properties. Highly recoverable energy storage density (Wrec ~ 3 J/cm3) and efficiency (η ~ 75%) are acquired in (NBT-BT)-0.06BZN ceramics under a low applied electric field of 210 kV/cm. Furthermore, superior temperature stability (20–120 °C), and frequency (1–1000 Hz) stability, and fatigue endurance (105 st) are also gained. These advantages further suggest that the (NBT-BT)-0.06BZN ceramics exhibit great promise in pulsed power markets.

Ferroelectric thin films capacitors have been potentially applied in advanced electronics and electric power systems because of their high power densities and fast charge–discharge responses. However, continuous operation of the ferroelectric thin film capacitors under elevated temperatures and high electric fields still remains a huge challenge. Herein, we report eco-friendly BiFeO3-modified Bi3.15Nd0.85Ti2.8Zr0.2O12 (BNTZ) free-lead ferroelectric thin films for high-temperature capacitor applications that simultaneously possess high-energy storage density (Wreco), efficiency (η), and temperature-dependent stability. The BNTZ–0.09BFO thin film shows a first-class-level Wreco (∼124 J cm−3) along with high η (∼81.9%), which surpasses almost all the Pb-contained and Pb-free perovskite ferroelectrics. Of particular importance is that excellent fatigue endurance for long-term stability (109 cycles) and thermal stability (−100 °C to 200 °C) could be achieved. This work represents a new design paradigm to exploit advanced dielectric capacitor materials for high-temperature electronics and energy storage devices.

Thermal stability of capacitors with both superior recoverable energy density (Wrec) and efficiency (η) have recently attracted great research interest for application in the pulse power systems. Here, high-quality lead-free relaxor-ferroelectric (RFE) (1-x)Bi0.5Na0.5TiO3-x(Na0.73Bi0.09)NbO3 [(1-x)BNT–xNBN, x = 0.10–0.18 ] ceramics are fabricated through solid-state reaction method. The NBN substitution of NBT ceramics could improve effecitively breakdown strength (BDS), energy storage performances, and the thermal stability. Especially, excellent recoverable energy density (Wrec ~ 2.41 J/cm3) and efficiency (η ~ 81.6%) could be achieved synchronously in 0.84BNT–0.14NBN ceramic. Moreover, the good thermal stability (20 °C ~ 140 °C), frequency stability (1–1000 Hz), and fatigue endurance (104 cycles) are also obtained in the composition of x = 0.14 ceramic. Particularly, corresponding ceramic shows high current density (~ 817 A/cm2), discharge energy density (~ 0.729 J/cm3), extremely short discharge rate (

In today's global traditional energy shortage environment, developing renewable and environmental-friendly energy has become a trend. In this work, the (1-x)Na0.5Bi0.5TiO3-xSr0.7Bi0.2TiO3 ((1-x)NBT-xSBT, x=0.2, 0.3, 0.4, and 0.5) relaxor ferroelectric thin films are grown on Pt/Si/SiO2 substrate via the sol-gel method. The structure, dielectric properties, energy density, thermal stability, frequency stability, and fatigue endurance for long-term stability of the (1-x)NBT-xSBT thin films are studied systematically. The experimental results demonstrate that the NBT-0.5SBT thin film exhibits an excellent discharge energy density (Wrec ~35.014 J/cm3) and efficiency (η ~73.8%) under 3200 kV/cm at room temperature (RT). More importantly, the corresponding thin film display superior the thermal stability (20–140 °C), frequency stability (102–104 Hz), and fatigue endurance for long-term stability (104 st). Therefore, this contribution will provide a convenient and efficient way for preparing high-performance dielectric capacitors for application in power pulse systems.

The development of lead-free bulk ceramics with high recoverable energy density (Wrec) and high efficiency plays a major role in meeting the requirements for miniaturization and integration of advanced pulsed power capacitors. In this study, composition-dependent phase structures and ferroelectric properties of lead-free relaxor ferroelectric ceramics (1 − x)(0.84Bi0.5Na0.5TiO3–0.16K0.5Bi0.5TiO3)–x(Bi0.2Sr0.7TiO3) [(1 − x)(BNT–KBT)–xSBT, x = 0–0.45] are investigated. The introduction of SBT into the morphotropic phase boundary (MPB) BNT–BKT system constructs the relaxor ferroelectrics according to the order–disorder theory, leading to an improved energy storage performance. Results show that an ultrahigh recoverable energy density of 4.06 J cm−3 and a high energy-storage efficiency of 87.3% under an electric field of 350 kV cm−1 are achieved concomitantly, together with a superior high temperature stability (30–160 °C) and strong fatigue endurance (104 cycles). In particular, the corresponding ceramic exhibits an ultrafast discharge rate (τ0.9 = 127 ns) and a high level of discharge energy density (Udis = 1.29 J cm−3). Our study provides the groundwork for an effective way to design high-performance ceramics for application in next generation energy storage capacitors.

High-temperature electrostatic capacitors are in urgent demand owing to the rapid development of advanced power electronic applications. However, obtaining polymer films with excellent discharge energy density and efficiency is still a huge challenge under harsh environmental conditions. Here, novel Ag nanodot/polyimide (Ag-ND/PI) nanocomposite films are designed and prepared through an in situ method. The energy storage capability and thermal stability of the PI matrix are significantly improved via loading a small amount of Ag-NDs, owing to the Coulomb-blockade effect and high thermal conductivity. Particularly, a high discharge energy density (Ud) of 5.16 J cm−3 at 600 MV m−1 is achieved for nanocomposite films with an ultralow filler content of 0.1 vol% Ag-NDs at room temperature, which is 260% higher than that of the pristine PI (2.02 J cm−3 at 450 MV m−1). Concurrently, the corresponding nanocomposite films exhibit an excellent high-temperature Ud of 2.56 J cm−3, together with efficiency exceeding 80% at a temperature of 150 °C at 400 MV m−1. Therefore, this research unveils a new method towards high-performance polymer capacitors for high-temperature applications.

Electromagnetic wave absorbing materials have been widely applied in the wireless communication, electronic devices, and radar technology. In this work, metal-organic frameworks derived nanoporous Fe3O4 @ carbon (Fe3O4@NPC) composites were successfully obtained by a simple method. Electromagnetic wave absorbing performances were significantly enhanced due to the optimal impedance matching and strong attenuation via the synergy between the dielectric loss and the magnetic loss. As a result, the Fe3O4@NPC composites exhibited excellent electromagnetic wave absorbing properties, in which a strong reflection loss (RL) of −65.5 dB at 9.8 GHz as well as a wide absorbing bandwidth of 4.5 GHz (RL

Electrostatic capacitors with a high dielectric constant and breakdown strength are desired for dielectrics to achieve a higher discharged energy density. Here, we propose that an artificial polymer nanocomposite combining a novel hybrid structure of one-dimensional Ag@BaTiO3@polydopamine@Ag nanofibers (1D ABPAs) as fillers and poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] as the matrix demonstrated a remarkably comprehensive performance. A large displacement (9.84 μC cm−2 at 480 MV m−1) was observed so as to obtain a high discharged energy density (∼17.25 J cm−3) of the composite films with 3 vol% 1D ABPAs, which was 2.22-times that of pristine P(VDF-HFP) (∼7.74 J cm−3). This discharged energy density is among the highest under an equivalent electric field strength reported so far. The corresponding composite films exhibited a superior charge/discharge speed of 139 ns and excellent reliability in energy storage performance by consecutive cycling. This work could provide an effective way to design and improve the performance of polymer-based nanocomposites for capacitive energy-storage applications.

With rapid developments in the consumer electronics market, electrostatic capacitors need to store as much energy as possible within a rather restricted space. In this work, nanocomposite films combining two-dimensional core–shell NaNbO3@Al2O3 platelets (2D NN@AO Ps) and poly(vinylidene-fluoride hexafluoropropylene) (P(VDF-HFP)), featuring excellent energy storage capability, high efficiency, and ultrafast discharge performance, are designed and fabricated. Both the experimental results and finite element simulations confirm the superiority of these 2D NN@AO Ps nanocomposite films in improving the breakdown strength (Eb) and energy storage capability. In particular, the introduction of 3 vol% 2D NN@AO Ps results in much enhanced discharge energy density of 14.59 J cm−3 and outstanding discharge efficiency of 70.1% in NN@AO Ps/P(VDF-HFP) nanocomposite films, which is much greater than that of pure P(VDF-HFP) (7.74 J cm−3). The corresponding nanocomposite films exhibit excellent reliability in energy storage performance under consecutive cycling. Therefore, this research could reveal a new chapter in the study and application of polymer nanocomposites in energy-storage dielectric capacitors.

High-performance capacitors, which have high energy storage density as well as high discharge efficiency, are desired. In this study, we have designed and prepared novel and high quality (1 − x)(0.65Bi0.5Na0.5TiO3–0.35Bi0.1Sr0.85TiO3)–x(K0.5Na0.5NbO3) [(1 − x)(BNT–BST)–xKNN, x = 0, 0.04, 0.06, 0.08, and 0.10] ceramics that demonstrated a remarkable energy storage capability, high efficiency, and ultrafast discharge speed. Particularly, the 0.94(BNT–BST)–0.06KNN ceramic possessed an excellent stored energy storage density (Ws = ∼3.13 J cm−3) and recoverable energy storage density (Wr = ∼2.65 J cm−3), and maintained a relatively high efficiency (η = ∼84.6%) at a relatively low electric field of 180 MV m−1, which is superior to those of the lead-free BNT-based energy-storage materials. Moreover, excellent temperature (20–120 °C) and frequency (1–100 Hz) stabilities of the 0.94(BNT–BST)–0.06KNN ceramic were also achieved. More importantly, the 0.94(BNT–BST)–0.06KNN ceramic exhibited an ultrafast discharge rate (τ0.9 = ∼1.01 μs), a high level of discharge energy density (Wd −1.21 J cm−3), and excellent reliability in energy storage performance by consecutive cycling. Moreover, this study also provides an effective approach to attain large energy-storage capability along with high efficiency in BNT-based ceramics for application in pulsed power capacitors.

For superior performance capacitors, large discharge energy density along with high discharge efficiency, high power density, and ultrafast charging/discharging speed are desired. Herein, we design and prepare new high quality nanocomposite films containing linear dielectric core–shell SrTiO3@Al2O3 nanofibers (ST@AO NFs) and poly(vinylidene fluoride) (PVDF) demonstrating remarkable energy storage performance. The experimental and finite element simulation results suggest that the incorporation of amorphous AO between the ST NFs and PVDF matrix could effectively improve the electric field strength, electric potential distribution, and current density of the nanocomposite films, resulting in greatly enhanced energy density and discharge efficiency. More importantly, the nanocomposite films loaded with 5 vol% ST@AO NFs show an outstanding discharge energy density of 15.3 J cm−3 at 475 MV m−1 and maintain a high discharge efficiency of 68.52%. Moreover, the corresponding nanocomposite films illustrate an ultra-fast discharge rate of 127 ns. The promising overall dielectric properties offer a new insight into the development of next-generation dielectric capacitor materials.

Electrostatic capacitors based on dielectrics are ubiquitous components for applications in modern electronics and electric power systems. However, the relatively low energy density of electrostatic capacitors, which is one or two orders of magnitude lower than that of the batteries, has greatly hindered the implementation of its in energy storage devices. Here, we propose a strategy to overcome the tradeoff between high polarizability and breakdown electric field, and attain great enhancement energy storage density in the lead-free (Ba2Bi3.97Pr0.03Ti5O18/BiFeO3)N (BBPT/BFO)N multilayer ferroelectric thin films with different BFO layers through interface engineering. The interface engineering could be utilized to concurrently modify both polarization and local electric field strength caused by the synergistic effect of multiple polar structures and electric field amplifying effect. Accordingly, the discharged energy density of the optimized (BBPT/BFO)1 ferroelectric thin-film capacitors as high as ∼ 79.3 J/cm3 with discharged efficiency exceeding ∼ 75 % are achieved. Combined with its fatigue-free, favorable temperature and frequency stabilities, the multilayer ferroelectric thin films of BBPT/BFO could be a promising dielectric material for practical energy storage applications.

The majority of the previously reported nanocomposites obtainable with higher energy density (>15 J cm−3) relies strongly on much higher breakdown strength (>4000 kV cm−1). The operation of capacitors in such higher applied electric field brings challenges because of the substantially increased the failure probability. In this study we explored the dispersibility and the orientation of fillers in nanocomposites as they play vital roles in the energy density. Based on the infinite element modulation results, an original design of 1–3 type composite structure was employed in the current study. This design adopts the one-dimensional (110)-oriented monodispersed barium strontium titanate Ba0.67Sr0.33TiO3 (BST) nanorod array as fillers embedded in the three-dimensional poly (−vinylidene fluoride) (PVDF) polymer matrix. With these originally designed BST/PVDF nanocomposites, we have demonstrated a significant enhancement of energy density at a lower applied electric field. For example, an energy density of 13.10 J cm−3 at electric field of 3400 kV cm−1 can be obtained, an enhancement of 3 times larger than that of bare PVDF. Moreover, the discharge efficiency is maintained at 69% at 3400 kV cm−1. The high performance of this originally designed nanacomposite demonstrated its potential application in the next generation energy storage devices.

Substantial attention for dielectric ceramic capacitors toward lead-free has been driven by the enhanced awareness of environmental protection. However, the unsatisfying breakdown strength (Eb) and comparatively low efficiency (η) becomes an obstacle for their widespread application. Here, environment-friendly lead-free relaxor ferroelectric (1-x) (0.67BiFeO3-0.33Ba0.8Sr0.2TiO3) -xSr0.7La0.2TiO3+0.1 wt.% MnO2 (BFO-BST-SLT) ceramic is reported as an efficient route to possess excellent Eb and high η simultaneously. The doping of SLT can significantly suppress the grain growth, improve the relaxation behavior, and thus increasing the Eb and η of the ceramics. Consequently, the corresponding ceramics with x=0.3 achieves good discharged energy density of ~ 2.55 J/cm3 and ultrahigh η of ~ 92%. Notably, it presents outstanding charging/discharging performances with fast charging/discharging time (~ 0.0266 μs), power density (~ 28.11 MW/cm3) along with current density (~ 468.5 A/cm2). Together with great temperature stability, frequency stability and cycle stability, this contributes provides a crucial way to prepare lead-free dielectrics for next-generation pulsed power capacitor applications.

Dielectric capacitors play a key role in revolutionizing modern electronic and electrical devices. Among these capacitors, anti-ferroelectric (AFE) capacitors receive much attention due to nonlinear dielectric properties and high-power output. (Pb0.89Ba0.08La0.02)(Zr0.50Sn0.40Ti0.10)O3 AFE ceramic with excellent dielectric nonlinearity was prepared via the solid state reaction, and the influence of dielectric response on discharge properties of AFE ceramics was studied. The results showed that dielectric constant (e) increased first and then decreased with electric field increasing and presented two peaks at 11.4 kV/cm and 16.9 kV/cm, corresponding to AFE–ferroelectric (FE) phase transition. Below 16.9 kV/cm, or before the AFE–FE phase transition, the discharge current increased. Beyond 16.9 kV/cm, or after AFE–FE phase transition, the current raised weakly and reached about 120A at 50 kV/cm, and it was hard to continue to increase the current after AFE–FE phase transitions. Therefore, dielectric response in AFEs had a great influence on the discharge performance. The results provided a simple method to select the appropriate working electric field for the practical application of AFEs capacitors.

Electrostatic capacitors with high power density have been demonstrated as efficient power sources in modern electrical and electronic devices. Nevertheless, the low energy density restricted the applications of electrostatic capacitors in the ever-developing electronic world. To improve energy density, herein, one-dimensional (1D) NaNbO3 (NN) nanowires with a high-aspect-ratio are prepared by a simple hydrothermal method and introduced into a poly(vinylidene fluoride) (PVDF) matrix. The NN@PDA nanowires/PVDF nanocomposite films show a high discharge energy density of 12.26 J cm−3 at 410 MV m−1, which is about 107% higher than that of pristine PVDF (5.87 J cm−3 at 350 MV m−1) and 510% higher than that of the best commercial biaxially-oriented-polypropylenes (BOPP) (2 J cm−3 at 640 MV m−1). Moreover, the composite films show a superior power density of 2.01 MW cm−3 and ultra-fast discharge speed of 146 ns. As verified by finite element simulations, 1D NN nanowires incorporation into the polymer matrix could significantly improve the local electric distribution and electric current density distribution in the nanocomposites. Ultimately, it is anticipated that this work will open a new design paradigm to boost the performance of polymer nanocomposites for compact and flexible electrical energy storage applications.

To reach the full potential of polymer dielectrics in advanced electronics and electrified transportation, it calls for efficient operation of high-energy-density dielectric polymers under high voltages over a wide temperature range. Here, the polymer composites consisting of the boron nitride nanosheet/polyetherimide and TiO2 nanorod arrays/polyetherimide layers are reported. The layered composite exhibits a much higher dielectric constant than the current high-temperature dielectric polymers and composites, while simultaneously retaining low dielectric loss at elevated temperatures and high applied fields. Consequently, the layered polymer composite presents much improved capacitive performance than the current dielectric polymers and composites over a temperature range of 25-150 °C. Moreover, the excellent capacitive performance of the layered composite is achieved at an applied field that is about 40% lower than the typical field strength of the current polymer composites with the discharged energy densities of >3 J cm-3 at 150 °C. Remarkable cyclability and dielectric stability are established in the layered polymer nanocomposites. This work addresses the current challenge in the enhancement of the energy densities of high-temperature dielectric polymers and demonstrates an efficient route to dielectric polymeric materials with high energy densities and low loss over a broad temperature range.

Polymer-based dielectric materials with high power density, high energy density, and broad operating temperature range are critical to the development of cost-efficient and lightweight capacitors for modern high-power electrical systems. Here, NaNbO3 (NN)/polymer composites, especially two-dimensional (2D) NN platelets, were used to create new composite films for energy storage applications for the first time. The trilayered architecture composites comprised of two outer layers of 2D NN platelets dispersed in a poly(vinylidene fluoride) (PVDF) matrix to provide high dielectric constant and a middle layer of pristine PVDF to offer high breakdown strength. The breakdown strength and energy density of the trilayered architecture composite films were improved significantly via tailoring the contents of the 2D NN platelets. The composite films with an optimized filler content illustrate a high discharge energy density of 13.5 J cm−3 at 400 MV m−1, far more than the best commercial biaxially- oriented polypropylenes. Moreover, the composite films show a superior power density of 2.68 MW cm−3 and ultra-fast discharge speed of 0.127 μs. Finite element simulation further revealed the breakdown strength and energy density of the composite films were much enhanced compared to the corresponding single layer composite films. Therefore, the new trilayered architecture composite films can be applied as an alternative promising high-performance electrostatic capacitor material.

In this work, [ x SrO, (1 − x )BaO]-K 2 O -Nb 2 O 5 -SiO 2 (SBKNS, x = 0.2, 0.4, 0.6, 0.8) glass-ceramics were synthesized through the controlled crystallization method. The phase structure, dielectric and energy-storage properties were systematically studied through the Sr substitution for Ba. It was found that the dielectric properties were improved due to the formation of solid liquid phase Sr 0.5 Ba 0.5 Nb 2 O 6 . Breakdown strength firstly increases and then decreases, which strongly depends on the variation in interfacial polarization. The highest value of breakdown strength reaches 1828 ± 88 kV/cm for x = 0.4, which is attributed to more uniform and dense microstructure and lower interfacial polarization. Correspondingly, the optimized theoretical energy-storage density reaches up to 17.45 ± 0.74 J/cm 3 . The maximum of discharged energy-storage density of 1.45 J/cm 3 from P-E loop was acquired under electric field of 500 kV/cm. Moreover, discharged power density of the capacitor was evaluated and reached a high value of 1.76 MV/cm 3 in pulsed charged-discharged circuit.

In this work, (100-x)(0.12 SrO-0.3 Na2O-0.1 Nb2O5)-xSiO2 (x = 30, 35, 40, 45, 50 mol%) glass-ceramics were prepared by using the meth-quenching-controlled crystallization method. Phase evolution, Crystallization mechanism, dielectric properties, dielectric breakdown strength (DBS), and energy-storage performances were comprehensively studied by varying SiO2 content. DSC studies revealed simultaneous occurrence of surface and internal crystallization mechanism in the glass-ceramics. XRD results showed three tungsten bronze structure SrNb2O6, Sr6Nb10O30, NaSr2Nb5O15 phases and perovskite structure NaNbO3 phase, which was quantified by the Reietveld refinement. It was found that dielectric constant and theoretical energy-storage density increased firstly and then decreased with the increase of the SiO2 contents. For x = 35 mol%, the theoretical energy-storage density reaches the maximal value of 15.3 J/cm3 due to the highest dielectric constant of 124 and DBS of 1669 kV/cm. And the highest DBS is related to the uniform and dense microstructure for x = 35 mol%. For practical applications in pulsed RLC circuit, the discharged efficiency increases from 74.2% to 91.5% with the increase of the SiO2 contents.

The SrO-Na 2 O-Nb 2 O 5 -SiO 2 (SNNS) glass-ceramics were prepared through the melt-quenching combined with the controlled crystallization technique. XRD results showed Sr 6 Nb 10 O 30 , SrNb 2 O 6 , NaSr 2 Nb 5 O 15 with tungsten bronze structure and NaNbO 3 with the perovskite structure. With the decrease of crystallization temperature, dielectric constant firstly increased and then decreased, while breakdown strength (BDS) was increased. High BDS of the glass-ceramics is attributed to the dense and uniform microstructure at low crystallization temperature. The optimal dielectric constant of 140±7 at 900 °C and BDS of 2182±129 kV/cm at 750 °C were obtained in SNNS glass-ceramics. The theoretical energy-storage density was significantly improved up to the highest value of 15.2±1.0 J/cm 3 at 800 °C, which is about 5 times than that at 950 °C. The discharged efficiency increased from 65.8% at 950 °C to 93.6% at 750 °C under the electric field of 500 kV/cm by decreasing crystallization temperature.

Electrostatic capacitors have been applied into high-power-density pulsed power systems comprising moderate energy density and ultrafast charging/discharging in the order of magnitude with a few milliseconds. In this article, different BaTiO3 nanostructures (e.g., nanoparticles, nanofibers, nanotubes, core–shell structure nanofibers) were synthesized and used to prepare polymer composite films in the poly(vinylidene fluoride) (PVDF) matrix. The effects of BaTiO3 nanostructures on the dielectric constant, dielectric loss, alternating current conductivity, breakdown strength, energy density, and mechanical properties of nanocomposites were investigated systematically. The largest dielectric constant of 17.14 was found in the 4 vol % BaTiO3 nanotube/PVDF nanocomposites. The BaTiO3@Al2O3 nanofiber/PVDF nanocomposites show the highest energy density of 12.37 J cm–3 at 450 MV m–1, ultrafast discharge speed (0.32 μs), and good mechanical properties. This article could open up a convenient and effective way for p...

Phase evolution, dielectric properties, breakdown strength, and energy-storage performance were studied by varying K 2 O content in K 2 O-BaO-Nb 2 O 5 -SiO 2 glass-ceramics. It was found that dielectric loss with the increase of K 2 O content increases owing to the un-crystallized K 2 O into the glass network, while dielectric breakdown strength firstly increases and then decreases due to the competition between two physical mechanisms, i.e., interfacial polarization and bridging-oxygen bond broken by the non-bridging oxygen ions. With the increase of K 2 O content, energy-storage density firstly increased up to 12.06±0.69 J/cm 3 with a high breakdown strength of 1973 kV/cm, and then decreased. Also, the discharged efficiency is obtained as a high value of 92% from P-E hysteresis loops.

High-temperature lead-free dielectric ceramic capacitors are urgently needed in modern advanced power electronics systems. However, it is still a great challenge to realize both ultrahigh energy density (Wrec) and efficiency (η) under the harsh environment. In this work, the innovative 0.9(Sr0.7Bi0.2)TiO3-0.1Bi(Mg0.5Zr0.5)O3 (SBT-BMZ)-modified BaTiO3 (BT) relaxor ferroelectric ceramics are ingeniously designed and synthesized via a solid-state reaction route. Optimal energy storage performances are attained in 0.65BT-0.35(SBT-BMZ) ceramic with an excellent Wrec of 4.03 J/cm3, couple with an ultrahigh η of 96.2% at 370 kV/cm, which are superior to other lead-free BT-based ceramics. The energy storage performances of the 0.65BT-0.35(SBT-BMZ) ceramic also display superior thermal stability (20 ~ 180 °C) with a subtle change of Wrec (±8%) and η (±1%), frequency stability (1 ~ 500 Hz) and cycle stability (1 ~ 106 cycles) at 200 kV/cm. Moreover, the charge and discharge experiments indicate that the outstanding power density (PD ~ 62.6 MW/cm3) and ultrafast discharge time (t0.9 ~ 62 ns) are also achieved. All these features demonstrate that the 0.65BT-0.35(SBT-BMZ) ceramic is expected to be widely used in next-generation of wide-temperature dielectric capacitors.

Electrostatic capacitors with excellent energy storage capacity and great thermal stability have become the researching focus. However, high-energy–density electrostatic capacitors are restricted through insurmountable drawbacks of low charge–discharge efficiency under high temperature/voltage working conditions. Herein, polyetherimide (PEI) nanocomposite films contains with two-dimensional boron nitride nanosheets (h-BNNS) are fabricated by solution casting method. Consequently, h-BNNS/PEI nanocomposite films exhibit tremendously breakdown strength (Eb ~ 700 MV/m), accompany with a record discharge efficiency (η ~ 93.6%) at room temperature with filler content of 4 vol%. The simulations and experiments results suggest that the h-BNNS loading into the PEI matrix could efficiently improve the high-temperature endurance. Particularly, the composites films exhibit superior comprehensive capacitive properties, e.g., discharged energy density of 3.43 J/cm3 along with η of 90.1% under 500 MV/m and 150 °C. Therefore, these characteristics render our polymer film an ideal material candidate for high-performance dielectric applications at evaluated temperature.

Electrostatic capacitors with simultaneously excellent recoverable energy density (Wrec) and efficiency (η), and wide operate temperature range are currently the main challenge in applications of modern electronics and electrical power systems. Here, a series of lead-free relaxor-ferroelectrics 0.85[(1-x)Bi0.5Na0.5TiO3-xBi0.1Sr0.85TiO3]-0.15KNbO3 ceramics with superb energy storage properties are prepared using solid-state reaction method. An excellent Wrec of 3.72 J/cm3 accompany with high η of 90.7% is attained concurrently with the composition of x = 0.3 under 290 kV/cm, which show remarkable advantages over recently reported lead-free ceramics. Meanwhile, superior thermal stability (20–200 °C) and frequency stability (1–1000 Hz) are also achieved. Moreover, by means of charge–discharge evaluations, the stored energy is released in an extremely short discharge time of 55 ns, regardless of variations in the temperature. All these characteristics demonstrate that this ceramic can be considered promising candidates for high power energy storage applications over broad temperature range.

Improving thermal stability of high-performance polymer-based nanocomposite films for electrical energy storage is essential to meet ever-increasing demands for the electrical industry, especially at harsh environment applications. Here, the polyetherimide (PEI)-based composites films are prepared via grafting method in the presence of SrTiO3 (ST) nanofillers to substantially improved capacitive performances at elevated temperature. The composites films with the optimized filler compositions show a high discharged energy density of 6.76 J/cm3 under 600 MV/m at room temperature. Meantime, excellent high-temperature discharged energy density of 6.6 J/cm3 at 100 °C for the composites films is also achieved, which is superior to most of the previously reported. The simulations further demonstrate that the ST nanoparticles embedded into the composites films could effectively improve heat dissipation in comparison with pristine PEI matrix, resulting in enhancement high-temperature energy storage capabilities. This work gives considerable promise for high energy density polymer-based nanocomposite films capacitors under harsh environments.

Next-generation advanced electronic markets demand high energy-storage properties dielectric materials that can operate efficiently under elevated temperatures. Here, the Sr0.85Bi0.1TiO3 modified Bi0.4465Na0.4465Ba0.057La0.05TiO3 ceramics ((1-x)BNBLT-xSBT) are designed to achieve excellent comprehensive energy storage performances. The phase field simulations and experimental results indicate that the SBT doping into BNBLT ceramics could effectively decrease grain size, resulting in enhancement breakdown strength. Consequently, excellent comprehensive performances via a superior balance between recoverable energy density (Wrec ~ 4.55 J/cm3) and efficiency (η > 90%) values have been realized in x=0.25 compositions. The corresponding ceramics exhibit impressive temperature stability (20~200 °C), fatigue endurance (105 st), and frequency stability (1~1000 Hz). More importantly, the BNBLT-0.25SBT ceramic shows a high power density (38.1 MW/cm3) and a record discharge rate (45 ns). Therefore, this work will provide a simple and effective method to develop a new category of dielectric capacitors with superior energy-storage performances over an extended temperature range.

The niobate-based glass-ceramics with a high energy storage density were prepared by using the controlled crystallization technology in the (Na2O, SrO) Nb2O5 SiO2 glass-ceramics. The dielectric properties, energy storage density, and discharge properties were investigated with the variation of the Na/Sr molar ratio. By varying the Na/Sr ratio, the energy storage density raises up to a high value of 10.09 J/cm3. With the variation of the Na/Sr ratio, both dielectric breakdown strength and discharge efficiency have an opposite change trend with the activation energy that reflects the interface polarization of the glass-ceramics. In contrast, for Na/Sr = 1/2, the glass-ceramic has the lower activation energy, which indicates that its interfacial polarization is weaker due to a fine microstructure. Thus, the glass-ceramics for Na/Sr = 1/2 have the characteristics of the higher breakdown strength of 2074 kV/cm and the higher discharge efficiency of 90.1%. Then it may contribute to the high energy storage density capacitor.

Two-step crystallization process was employed to improve microstructure and energy-storage density of the strontium barium niobate-based/titanate-based glass-ceramics. By using two-step crystallization process, the optimum nucleation temperature was obtained to improve dielectric breakdown strength. Compared to the breakdown strength by one-step crystallization process, the breakdown strength by two-step crystallization process is increased about 1.89 times with the optimum nucleation temperature. Energy-storage density of 7.73 ± 0.26 J/cm3 is significantly improved by two-step crystallization process and is about 2.9 times of 2.63 ± 0.17 J/cm3 by one-step crystallization process. This result is attributed to the homogeneous nucleation improving the microstructures of glass-ceramics. Identification and quantification of crystalline phases by using Rietveld refinement reveals the difference of dielectric constants for one-step and two-step crystallization processes.

A novel inorganic/polymer nanocomposite, using 1-dimensional TiO2 nanorod array as fillers (TNA) and poly(vinylidene fluoride) (PVDF) as matrix, has been successfully synthesized for the first time. A carefully designed process sequence includes several steps with the initial epitaxial growth of highly oriented TNA on the fluorine-doped tin oxide (FTO) conductive glass. Subsequently, PVDF is embedded into the nanorods by the spin-coating method followed by annealing and quenching processes. This novel structure with dispersive fillers demonstrates a successful compromise between the electric displacement and breakdown strength, resulting in a dramatic increase in the electric polarization which leads to a significant improvement on the energy density and discharge efficiency. The nanocomposites with various height ratios of fillers between the TNA and total film thickness were investigated by us. The results show that nanocomposite with 18% height ratio fillers obtains maximum increase in the energy densi...

Inorganic/polymer nanocomposites, using one-dimensional (1D) core–shell structure BaTiO3@Al2O3 nanofibers (BT@Al2O3 nfs) as fillers and poly(vinylidene fluoride) (PVDF) as the polymer matrix, have been prepared. The core–shell structure BT@Al2O3 nfs have been synthesized via coaxial electrospinning. The breakdown strength (Eb) and discharged energy density of the nanocomposites can be significantly improved by creating an insulating Al2O3 shell layer with moderate dielectric constant on the surfaces of BT nanofibers to form a moderate interfacial area. The Al2O3 shell layer could effectively confine the mobility of charge carriers, which reduces energy loss by reducing the Maxwell–Wagner–Sillars (MWS) interfacial polarization and space charge polarization between the fillers and the polymer matrix. As a result, the nanocomposite films filled with 5 vol% BT@Al2O3 nfs exhibit a excellent discharge energy density of 12.18 J cm−3 at 400 MV m−1, which is ≈254% over bare PVDF (4.8 J cm−3 at 350 MV m−1) and ≈1015% greater than the biaxially oriented polypropylenes (BOPP) (≈1.2 J cm−3 at 640 MV m−1). The work here indicates that this promising state-of-the-art method of preparing high energy density nanocomposites can be used in the next generation of dielectric capacitors.

Nanocomposites in capacitors combining highly aligned one dimension ferroelectric nanowires with polymer would be more desirable for achieving higher energy density. However, the synthesis of the well-isolated ferroelectric oxide nanorod arrays with a high orientation has been rather scant, especially using glass-made substrates. In this study, a novel design that is capable of fabricating a highly [110]-oriented BaTiO3 (BT) nanorod array was proposed first, using a three-step hydrothermal reaction on glass-made substrates. The details for controlling the dispersion of the nanorod array, the orientation and the aspect ratio are also discussed. It is found that the alkaline treatment of the TiO2 (TO) nanorod array, rather than the completing transformation into sodium titanate, favors the transformation of the TO into the BT nanorod array, as well as protecting the glass-made substrate. The dispersity of the nanorod array can be controlled by the introduction of a glycol ether-deionized water mixed solvent and soluble salts. Moreover, the orientation of the nanorod arrays could be tuned by the ionic strength of the solution. This novel BT nanorod array was used as a filler in a nanocomposite capacitor, demonstrating that a large energy density (11.82 J cm-3) can be achieved even at a low applied electric field (3200 kV cm-1), which opens us a new application in nanocomposite capacitors.

The structural, magnetic and magnetostrictive properties of TbxHo0.9-xNd0.1Fe1.93 (0 for x = 0.10 to for x = 0.25 through an intermediate direction around x = 0.15, subjected to the anisotropy compensation between Tb3+ and Ho3+ ions. The splitting of (440) XRD peak accompanied by the spontaneous magnetostriction-induced rhombohedral distortion is observed for the compounds of x >= 0.2, and the spontaneous magnetostriction coefficient Am is found to increase with increasing Tb content. The analysis of XRD, EMD, magnetization and magnetostriction shows that the pseudobinary system TbxHo0.9-xNd0.1Fe1.93 is an anisotropy compensation system and the compensation point is realized around x = 0.25. The Nd-containing Tb0.25Ho0.65Nd0.1Fe1.93 Laves-phase compound has good magnetostrictive properties, that is, a large saturation magnetostriction (lambda s similar to 585 ppm) and a low magnetocrystalline anisotropy at room temperature, which may make it technological interest for magnetostriction applications. (C) 2014 Elsevier B.V. All rights reserved.

Organic/inorganic nanocomposites (OINs) can be potentially used as high-performance capacitors due to their rapid charge-discharge capability along with respectable power density. The coupling effect of the filler/matrix interface plays a prominent role in the dielectric and electric properties of OINs. Along with a review of contemporary theoretical models, recent advances in interfacial optimization to improve energy density through careful interface control and design are also presented. Possible mechanisms that may improve energy density and potential applications for high-energy-density capacitors are also highlighted.