High-temperature Capacitors Research Articles

Correction to: Bi(Mg0.5Hf0.5)O3-modified SrTiO3 lead-free ceramics for high-temperature energy storage capacitors

Correction to: Bi(Mg0.5Hf0.5)O3-modified SrTiO3 lead-free ceramics for high-temperature energy storage capacitors

A novel poly(p-phenylene benzobisoxazole) (PBO)-based three-phase silk-cocoon network structure nanocomposites with enhanced dielectric properties

Nanocomposites with great thermal stability and excellent dielectric properties play a vital role in the development of high-temperature resistant capacitors. A facile yet effective method to synthesize enhanced dielectric properties of thermostable three-phase poly(p-phenylene benzobisoxazole) (mCCTO@CFGO/PBO) nanocomposite films is demonstrated in this work. The amino-functionalized oxide CaCu3Ti4O12 nanoparticles (mCCTO) are enwrapped by the carboxyl-functionalized ultrathin graphene shells (CFGO), forming the silk-cocoon structure to achieve homogeneous dispersion in the matrix. The final films are fabricated via in situ polymerization by introducing the mCCTO@CFGO nanoparticles into the PBO precursor polymer. The mCCTO@CFGO/PBO nanocomposite films exhibit high thermal stability (the 5% thermal decomposition temperature is 655 °C), while the unique silk-cocoon structure effectively confers the high dielectric constant up to 86.9 and ultra-low dielectric loss (0.063) with the loading of 10 wt% mCCTO@3 wt% CFGO/PBO at 1 kHz and 200 °C. This promising strategy accelerates the development of electronic devices used under high temperatures.

High-temperature resistant polypropylene films enhanced by atomic layer deposition

Last two decades has witnessed various technical programs towards the development of new dielectric films for high temperature and high energy density capacitor technology. Yet, the organic polypropylene film still holds its top position for film capacitors required for electric and electronic power applications such as power grid, hybrid electric vehicles, oil and gas exploration, and aviation. However, its low temperature stability determined by its structural nature limits its further adoption for more rising markets. This work thus developed a creative method (ultrathin coating of inorganic compound using atomic layer deposition) to increase the high temperature stability and the dielectric strength of such a strategically important polymer film from below 105 °C to above 140 °C. Several techniques also confirmed the effective minimization of the dimensional change and crystallinity loss at higher temperatures, i.e., Thermomechanical analysis, Dynamic mechanical analysis, Dynamic Scanning calorimetry, x-ray diffraction and electron microscopy techniques. This breakthrough discovery adds a huge value to the commercial PP films and relevant capacitor industry and will extend the operation of high-performance PP film capacitors to various high standard applications.

Dielectric and piezoelectric properties of lead-free Na0.5Bi0.5TiO3-SrTiO3-BiFeO3 ternary system

This work focuses on the synthesis and characterization of a Pb-free (0.8-x)Na0.5Bi0.5TiO3-0.2SrTiO3-xBiFeO3, 0.00 ≤ x ≤ 0.10 perovskite. The ceramics exhibit significant improvement in some of the key parameters like Tc, dielectric constant, temperature stability, TCε values, etc. XRD patterns suggest 100% perovskite structure (Pseudocubic phase) without any trace of secondary phases. The temperature-dependent dielectric constant of doped ceramics exhibits peculiar response particularly at lower frequencies with εr increasing drastically to extraordinarily large values (˃ 50,000 at 1 kHz, and ˃ 12,000 at 10 kHz). Such an abnormal behavior probably arises due to the interfacial polarization caused by the formation of defect dipoles. Further, successive dielectric anomalies appeared around 200–250 °C and 350–450 °C in the BFO doped samples giving rise to temperature-insensitive dielectric constant over a broad temperature span. The composition (x = 0.05) showed a permittivity of ~4000 at 100 kHz at 250 °C with a normalized permittivity Δε/ε250 varying not more than± 15% from 200 °C to beyond 500 °C. In addition, the same composition yields a TCε value as low as −194 ppm/°C which is promising from the application point of view. Analysis of P-E, J-E and S-E loops predict a probable destabilization of the ferroelectric phase by introduction of relaxor state with the incorporation of BFO in the complex perovskite solid solution. Based on the current results, the NBT-ST-BFO ceramics can be designed to minimize loss via compositional engineering for high-temperature capacitor applications.

Fabrication of bismuth silicate Bi2SiO5 ceramics as a potential high-temperature dielectric material

Bismuth silicate Bi2SiO5 (BSO) is known as an interesting new type of ferroelectric oxide; however, bulk ceramics of BSO have never been obtained because it easily decomposes at high temperature. In this study, we fabricated BSO ceramics for the first time using a sol–gel technique and investigated their potential as a dielectric material for high-temperature capacitor applications. A precursor powder was prepared by a sol–gel synthesis route using tetraethyl orthosilicate and bismuth nitrate pentahydrate as raw materials and then sintered under a small uniaxial pressure of 5 MPa with an addition of CH3COOLi as a sintering aid. A BSO ceramic with the highest relative density of 88.5% was obtained at a very low sintering temperature of 620 °C with preventing significant thermal decomposition. A crystal structure analysis revealed that the obtained BSO ceramic belongs to the ferroelectric monoclinic phase. The dielectric permittivity of the ceramic showed a superior temperature stability (± 5%) at temperatures up to 200 °C, followed by a sharp peak attributed to the ferroelectric–paraelectric phase transition at around 390 °C. The BSO ceramic also showed slim and pinched polarization hysteresis loops due to the random grain orientation and domain wall clamping, leading to a high energy storage efficiency over 75% at temperatures up to 100 °C.

High-temperature BaTiO3-based ternary dielectric multilayers for energy storage applications with high efficiency

High-temperature BaTiO3-based ceramic capacitors have broad application prospects in energy storage devices. However, energy density and efficiency of BaTiO3-based ceramic capacitors are bottleneck challenges that limit the applications of ceramic capacitors in the vast of industrial applications. To address this issue, it needs to design novel BaTiO3-based ceramics to elevate the breakdown strength, energy density and efficiency of capacitors. Here, high performance BaTiO3-based ceramics with breakdown strength of 290 kV cm−1, discharge energy density is more than 2.4 J cm−3, energy storage efficiency is achieve 91.5% are achieved in novel ternary system 0.88BaTiO3-0.12(1-x)Bi(Li0.5Nb0.5)O3-0.12xBi(Mg0.5Ti0.5)O3 (BT-BLN-BMT) (0.2 ≤ x ≤ 0.8) lead-free ceramic. Moreover, 0.88BT-0.12(1-x)BLN-0.12xBMT (x = 0.6) multilayer ceramics capacitors effectively increased breakdown strength and energy density values are more than 500 kV cm−1 and 4.42 J cm−3, improved by 488% and 1373% compared with only 85 kV cm−1 and 0.3 J cm−3 for the pure BaTiO3. It maintains high thermal stability in the temperature range from 25 °C to 150 °C. All these results have clearly collaborated the promising future of this novel BaTiO3-based ceramics in energy storage applications in the future.

Bi(Mg0.5Hf0.5)O3-modified SrTiO3 lead-free ceramics for high-temperature energy storage capacitors

Lead-free (1 − x)SrTiO3–xBi(Mg0.5Hf0.5)O3 (0.05 ≤ x ≤ 0.4) ceramics were prepared by high-temperature solid-state sintering method. The microstructure, dielectric properties, and energy storage performance were investigated. The diffused phase transition was observed in samples with x ≥ 0.1, showing typical relaxor characteristic. In particular, 0.8ST-0.2BMH composition exhibits stable dielectric permittivity with variation below 15% over temperature range of − 100 °C to 185 °C, superior to that of undoped SrTiO3. The calculated Weibull characteristic breakdown strength is 480 kV/cm for 0.8ST-0.2BMH ceramic, and a large energy density of 4.1 J/cm3 with high energy efficiency of 92% is obtained at electric field of 470 kV/cm. Of particular significance is that the energy efficiency remains above 91% at elevated temperature of 180 °C. In addition, fast discharge time (~ 0.88 µs) with high-power density of 2.8 MW/cm3 is achieved in 0.8ST-0.2BMH ceramic. All the above results indicate that the 0.8ST-0.2BMH relaxor dielectric is a promising lead-free ceramic for high-temperature energy storage applications.

Ultrahigh discharge efficiency and improved energy density in polymer-based nanocomposite for high-temperature capacitors application

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.

Substantially improved energy storage capability of ferroelectric thin films for application in high-temperature capacitors

The BNTZ–0.09BFO thin film shows superior energy density of 124 J cm−3 and efficiency of 81.9%, excellent fatigue endurance (109 cycles) and thermal stability (−100 °C to 200 °C).

Reducing dielectric loss in Na0.5Bi0.5TiO3 based high temperature capacitor material

The demand for capacitors exhibiting low sensitivity towards temperature changes and high power peaks has increased significantly. Recently, Na0.5Bi0.5TiO3 (NBT) based ceramics became excellent candidates for such extreme temperature capacitors. The dielectric loss of these materials is, however, difficult to control because of the complex defect chemistry of NBT based ceramics. Therefore, it is the limiting factor for high temperature applications. In this work, we present a strategy to increase the upper temperature limit for low dielectric loss. The addition of BiAlO3 to Na0.5Bi0.5TiO3-BaTiO3-CaZrO3 reduces the loss and sensitivity towards Bi evaporation during synthesis. For unmodified samples, the relative permittivity (εr = 581, at 1 kHz) varies less than 15 %, while the dielectric loss stays below 0.02 between -68 and 368 °C. With the addition of BiAlO3, the temperature range of low loss extends from -68 to 391 °C at even higher permittivity (εr = 628, at 1 kHz).

Significantly Improvement of Comprehensive Energy Storage Performances with Lead-free Relaxor Ferroelectric Ceramics for High-temperature Capacitors Applications

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.

Largely enhanced dielectric properties of polymer composites with HfO2 nanoparticles for high-temperature film capacitors

Polymer dielectrics are preferred materials for high-energy-density capacitive energy storage. In particular, high-temperature dielectrics that can withstand harsh conditions, e.g., ≥150 °C, is of crucial importance for advanced electronics and electrical power systems. Herein, high-temperature dielectric polymer composites composed of polyetherimide (PEI) matrix and hafnium oxide (HfO2) nanoparticles are presented. It is found that the incorporation of HfO2 with a moderate dielectric constant and a wide bandgap improves the dielectric constant and simultaneously reduces the high-field leakage current density of the PEI nanocomposites. As a result, the PEI/HfO2 composites exhibit superior energy storage performance to the current high-temperature engineering polymers at elevated temperatures. Specifically, the nanocomposite with 3 vol% HfO2 displays a discharged energy density of 2.82 J/cm3 at 150 °C, which is 77% higher than neat PEI. This work demonstrates the effectiveness of incorporation of the nanofiller with a medium dielectric constant into the polymer on the improvement of high-temperature capacitive properties of the polymer composites.

Optimization the energy density and efficiency of BaTiO3-based ceramics for capacitor applications

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.

Increased Energy-Storage Density and Superior Electric Field and Thermally Stable Energy Efficiency of Aerosol-Deposited Relaxor (Pb0.89La0.11)(Zr0.70Ti0.30)O3 Films

(Pb0.89La0.11)(Zr0.70Ti0.30)O3 (PLZT 11/70/30) relaxor ferroelectric (RFE) films were fabricated on Pt/Si substrates by aerosol deposition, which not only enabled the deposition of a film at room temperature but also increased the dielectric breakdown strength. Perovskite phase and microstructural analyses were carried out by x-ray diffraction and scanning electron microscopy techniques. A PLZT 11/70/30 RFE AD film annealed at 550 °C exhibited the best dielectric properties (er ~ 1090, tanδ ~ 0.028) and typical relaxor-type slim polarization–electric field (P–E) hysteresis loop with relatively low remanent polarization (Pr ~ 6.81 µC/cm2) and coercive field (Ec ~ 118 kV/cm) even at a high applied electric field (~ 2500 kV/cm). These superior properties were achieved due to high phase purity, low defect densities, and well-tuned grain sizes of an annealed PLZT 11/70/30 RFE AD film. The PLZT 11/70/30 RFE AD film exhibited a high energy-storage density (Wrec ~ 44 J/cm3) which is attributed to the high dielectric breakdown strength, low hysteresis loss (Wloss ~ 10.3 J/cm3), and almost-electric-field-independent efficiency (η ~ 81%, change of ~ 6% with the change from low to high electric fields), calculated using the unipolar P–E hysteresis loop. The excellent temperature stability of the energy efficiency of the PLZT 11/70/30 RFE AD film makes it a promising material for high-temperature energy-storage capacitor applications.

Enhanced dielectric properties in polyimide nanocomposites containing barium titanate@ polydopamine core-shell nanoparticles

In this work, we prepared the polyimide (PI) nanocomposite films containing barium titanate @polydopamine (BT@PDA) nanoparticles within a core-shell structure by solution casting method. The dielectric constant of these nanocomposite films is significantly improved compared to pure PI film, and increases with the increase of BT nanoparticles. And, the breakdown strength of these nanocomposite films is better than that of untreated BT/PI films at the fixed BT content. The PI composite film containing 1 vol% of BT@PDA nanoparticles exhibits the highest energy storage density of 1.94 J/cm3 under an electric field of 315 kV/mm, which is 42% over the pristine PI (1.37 J/cm3 at 295 kV/mm) and about 162% greater than biaxially-oriented polypropylene (BOPP) (≈1.2 J/cm3 at 640 kV/mm). The presence of PDA shell effectively improves the dispersion uniformity and interfacial compatibility of BT nanoparticles in the PI matrix, giving rise to lower local electric field distortion in the composites. Besides, the BT@PDA/PI nanocomposite films have excellent dielectric thermal stability in the temperature range from 25 to 200 °C and thermal stability up to 500 °C. The BT@PDA/PI composites fabricated in this work have a great potential to be used in the high-temperature film capacitors.

High thermally stable dielectric permittivity, polarization enhancement and electrostrictive properties in Zr-substituted bismuth sodium titanate lead-free ferroelectric ceramics

Zr-substituted (Bi0.5Na0.5)(Ti1−xZrx)O3 (BNTZ) with x = 0.02–0.4 ceramics were prepared using solid-state reaction technique and their structural, dielectric and ferroelectric properties were investigated systematically. X-ray diffraction results suggest that Zr4+ ion can enter the (Bi0.5Na0.5)TiO3 (BNT) crystal lattices at a limited value and a secondary phase appears in BNTZ ceramics when the x exceeds 0.1. Temperature-dependent dielectric permittivities of BNTZ ceramics show only one dielectric peak from room temperature to 500 °C for each composition, and this dielectric peak becomes broad gradually as x increases from 0.02 to 0.4. The permittivity of x = 0.4 varies less than ±10% between room temperature and 300 °C, indicating a superior thermal stability of the permittivity. Polarization enhancement is revealed by the polarization-electric field hysteresis loops and highest ferroelectric properties are obtained in x = 0.04. The electric-field-induced strains of x = 0.04 show a monotonous increase as temperature increases from 30 °C to 150 °C. At 80 kV/cm, a high strain level of 0.268% is achieved. Our results suggest that the introduction of Zr4+ ion could effectively tailor the dielectric and ferroelectric properties of BNT ceramics and x = 0.4 composition could find potential application in high temperature capacitor devices.

Origin of ultrahigh thermal stability on dielectric permittivity and dipole glass-like behavior of 0.4Ba0.8Ca0.2TiO3-0.6Bi(Mg0.5Ti0.5)O3 based ceramics

The 0.4Ba0.8Ca0.2TiO3-0.6Bi(Mg0.5Ti0.5)O3 (BCT-BMT) and 5 mol% Si doped 0.4Ba0.8Ca0.2TiO3-0.6Bi(Mg0.5Ti0.5)O3 (BCST-BMT) ceramics with a pseudo-cubic crystal structure were prepared. Both as-prepared and O2 annealing ceramics (BCT-BMT-O2 and BCST-BMT-O2) exhibit a typical re-entrant dipole-glass-like relaxor behavior and excellent thermal stability of dielectric permittivity above Tm. A statistical model was employed to describe the temperature dependence of dielectric permittivity, which reveals the origin of the special dielectric properties. The large dielectric permittivity is attributed to the weakly interacting polar nanoregions (PNRs) associated with complex ionic substitution of both the A-site and B-site. The ultrahigh thermal stability is related to the thermal distribution of active dipoles. The Si doped BCT-BMT ceramic shows that the capacitance variation are lower than ± 5 % (1209 ± 60) in a wide temperature range from 437 K to 796 K with a low dielectric loss (tanδ < 0.025) from 443 K to 714 K, indicating a promising material for use in high-temperature capacitors.

Dielectric and energy-storage properties in Bi0.5Na0.5TiO3-BaTiO3-AgNbO3 ternary perovskite compounds

A ternary perovskite dielectric (1 − x) ( 0.92Bi0.5Na0.5TiO3-0.08BaTiO3)-x AgNbO3 has been developed for application as high-temperature energy-storage capacitors. It is suggested that with increasing AN content, the material has experienced non-ergodic relaxor → ergodic relaxor → paraelectric state transformation. The most attractive properties are obtained in the composition x = 0.10 with superior high-temperature dielectric stability (er150°C = 1901, TCC150°C≤ 15% in 20–368 °C range) and optimized energy-storage performance (Wmax =1.07 J/cm3, ηmax = 78% at 10.4 kV/mm).

Polyimide films coated by magnetron sputtered boron nitride for high-temperature capacitor dielectrics

Polymers are widely used as dielectric materials in dielectric capacitors, which are the key component of various circuits in power electronic devices. The sharply increased conduction loss at elevated temperatures limits their high-temperature applications. To address this issue, here in this study boron nitride (BN)/polyimide (PI)/BN sandwich-structured films were developed by depositing BN of optimal thickness onto both sides of PI films using magnetron sputtering. Dielectric, insulating and energy-storage performance at 150 °C of the resultant composite films were investigated. The experimental results showed that a dense layer of hexagonal boron nitride (h-BN) was formed on the surface of the polyimide and the coating layer could effectively suppress the charge injection at the electrode/dielectric interfaces by improving the barrier height. Consequently, the sandwiched film of optimal BN thickness exhibited a declined leakage current of about one order of magnitude lower and an improved breakdown strength by 12% in comparison to the neat PI. The sandwiched film could discharge an energy density of 0.493 J/cm3 with charge-discharge efficiency of over 90% under an electric field of 200 MV/m at 150 °C, while the neat PI only possesses an efficiency of 72% and a much lower discharged energy density.

Synthesis of Superheat-Resistant Polyimides with Enhanced Dielectric Constant by Introduction of Cu(ΙΙ)-Coordination.

To achieve polyimide-metal complexes with enhanced properties, 5-amine-2-(5-aminopyridin-2-yl)-1-methyl-benzimidazole (PyMePABZ) that contains stiff 2-(2′-pyridyl)benzimidazole (PyBI) was synthesized and exploited to construct the Cu(ΙΙ)-crosslinked polyimides (Cu-PIs). These Cu-PIs exhibited higher dielectric, thermal, and mechanical properties with an increase in Cu2+ content. Among them, their dielectric constants (εrS) were up to 43% superior to that of the neat PI, glass transition temperatures (Tgs) were all over 400 °C, and 5% weight loss temperature (T5%) maintained beyond 500 °C. These data indicate that the metal coordination crosslinking provided a useful guide to develop high performance PIs which possess potential application as useful high temperature capacitors.