Electrical Breakdown Strength Research Articles

Dielectric, electrical and thermal properties of Sodium Molybdate-hexagonal Boron Nitride composites enabled by cold sintering

Advances in 5G and 6G communication technologies and their applications are in part limited by the capabilities of current electronic packaging materials, as expanded bandwidth is a pressing need for novel dielectric substrates capable of co-firing into packages and devices, characterized by low dielectric loss and enhanced thermal conductivity. This investigation provides further characterization in the dielectric, electrical and thermal conductivity properties over previously reported cold sintered composite of Sodium Molybdate Na2Mo2O7 (NMO) with hexagonal Boron Nitride (hBN), such as relative permittivity (εr) and dielectric loss (tan δ) values at high frequencies of 75–110 GHz, electrical resistivity (ρ) fitting to percolation theory, Weibull statistical analysis of electrical breakdown strength (Eb) and its anisotropic thermal conductivity (κ) influenced by the filler's crystal structure. The cold sintered composites were systematically characterized with respect to filler volume fraction, temperature, and frequency. The findings in this analysis position engineered composites as a promising alternative for microwave substrate materials, with using a densification method that limits interactions and maximizes densification, hence the demonstration with cold sintering.

Constructing a dual gradient structure of energy level gradient and concentration gradient to significantly improve the high-temperature energy storage performance of all organic composite dielectrics†

The severe electrical conduction loss at elevated temperature is the initial factor for the degradation of energy storage performance of polymer dielectric films, thus it urgently needs to develop highly heat-resistant polymer capacitive films for meeting the advancing electrical and electronic applications. For reducing conduction loss and improving the high-temperature energy storage performance of dielectrics, the current approaches are focusing on preventing carriers mobility at elevated temperature and high electric field. In this study, the molecular semiconductor ITIC (ITIC is an organic molecular semiconductor 2,2′-[[6,6,12,12-Tetrakis(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene-2,8-diyl]bis [methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propanedinitrile] abbreviation) with high electron affinity was filled into the blends of polyether imide (PEI) and polyethersulfone (PESU). The energy level gradient was constructed due to the different energy bandgap structures among ITIC, PESU and PEI. In addition, the concentration structure gradient was constructed due to the concentration of ITIC which varies along the thickness direction. The results demonstrate that the dual gradients of energy level and concentration can effectively inhibit carrier migration and lower conduction loss, thus significantly improving the electric breakdown strength and energy storage performance at high temperature. The energy storage densities (Ue) of 5.14 J/cm3 and 3.6 J/cm3 at 150 °C and 200 °C, respectively were achieved in PEI/PESU blends with 9 layers of ITIC gradient and 0.25 % ITIC in the outer layer. This study puts forward a novel structural design combining the energy levels gradient with concentration gradient to optimise the high-temperature energy storage properties of all-organic dielectric films.

Synergistic effect of positive temperature coefficient and thermally conductive micro‐nano fillers on electrical and thermal properties of epoxy resin

AbstractThis study investigates the effect of positive temperature coefficient (PTC) fillers, i.e., barium strontium titanate (BST‐60) and nano hexagonal boron nitride (h‐BN) fillers, on thermal and dielectric insulation properties of epoxy (EP). The electrical resistivity, DC breakdown strength, space charge, thermal conductivity, thermogravimetric analysis, and glass transition temperature (Tg) of EP composites were measured. Results indicate that, below curie temperature, the EP composites containing 0.5 and 1 wt% of BST and 5 wt% of h‐BN have superior electrical resistivity, breakdown strength, and thermal conductivity. However, above curie temperature, the EP composites containing 2 and 2.5 wt% of BST and 5 wt% of h‐BN have superior insulation properties than the pure EP and other composites. While the thermal properties of EP improve with an increase in h‐BN loading to 10 wt%, its dielectric properties are slightly compromised due to the presence of tiny defects in the composite material. It is hypothesized that the BST‐60 suppresses the negative temperature coefficient effect (NTC) of EP by regulating the electrical resistivity above the curie point, whereas nano h‐BN enhances the thermal conductivity of EP by constructing a heat dissipation path. The proposed mechanism for charge dynamics along with heat conduction‐dissipation explains the fillers' behavior at different temperatures.Highlights Analysis of epoxy composites with polydopamine‐modified BST and h‐BN fillers. PTC fillers are used to mitigate the negative temperature effect of epoxy. Optimal fillers wt% improves dielectric and thermal properties. This study shows that optimized epoxy composites can be used for packaging.

Ni-modified BaTiO3 film prepared by sol-gel with high energy storage performance

The development of lead-free dielectric capacitors with high recoverable energy storage density and high energy storage efficiency is important for improving the overall performance of electronic and power systems. BaTiO3 (BTO) is one of the most common ferroelectric materials and has attracted much attention for energy storage applications in the past decades due to its excellent dielectric and ferroelectric properties. However, high remnant polarization and low electrical breakdown strength of BTO limit its development in energy storage applications. Many efforts (e.g., elements doping, interface/heterostructure, etc.) have been made to improve the energy storage density of BTO thin films. In this paper, Ba1-xNixTiO3 thin films (x = 0, 0.02, 0.04, 0.06, 0.08; abbreviated as BNxT) were synthesized via sol-gel and spin-coated method. The effect of Ni doping on the structural, dielectric, ferroelectric and energy storage properties of BTO thin films has been studied. The results confirmed that with the increase of Ni doping, a second phase arises and the dielectric constant decreases. While appropriate Ni doping led to the improvement of the breakdown strength, further increase of Ni deteriorated the energy storage because of the high oxygen vacancy. Finally, optimized energy storage performance was obtained for BN0.04T thin film: dielectric constant of 401, dielectric loss of 0.002, recoverable energy density of 20.2 J/cm3 and energy storage efficiency of 83.6% at 965 kV/cm. Meanwhile, the remnant and maximum polarization of the films were 0.06 μC/cm2 and 50 μC/cm2, respectively. BN0.04T thin film has an excellent application prospect and is expected to appear as a component in the future composite energy storage film system.

Nano-Titanium Dioxide Filler Particles in Soybean Methyl Ester for an Improvement of Electrical Breakdown Strength of Soybean Vegetable Oil as a Transformer Oil Substitute

Power transformers use mineral oil as an insulating liquid due to its excellent dielectric properties. However, mineral oil is a non-renewable resource and is toxic to the environment when leaked. The purpose of this research is to examine vegetable oil containing nanotitanium dioxide as a substitute for mineral transformer oil. Vegetable insulating oils are environmentally benign and have good breakdown voltage (BV) and high ignition points that can decompose naturally in the event of a leak. Nevertheless, the high viscosity of vegetable oil slows down the flow rate in the transformer cooling. To overcome this problem, the process of transesterification was used to produce soybean methyl ester (SBME). SBME is used as an insulating liquid including composite filler of titanium dioxide (TiO2) nanoparticles. Electrical breakdown voltage (BV) tests were performed following ASTM D1816 standards. Results demonstrated that SBME has a greater BV than natural soybean oil. Also, the addition TiO2 nanoparticles increases the BV of the SBME’s mixture. All cases of nanoparticle methyl ester (NPME) conducted in the experiments exhibited a BV higher than 28 kV which is well above the standard value.

High energy storage performance of lead‐free Nb‐modified (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)TiO3 high‐entropy ceramics

AbstractOwing to the intrinsic chemical disorder of microscopic composition, perovskite high‐entropy ceramics exhibit dielectric relaxation behaviors and are favorable for energy storage performance. In this work, (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)(Ti1−xNbx)O3 (BNCBST‐xNb, 0.01 ≤ x ≤ 0.25) ceramics were prepared using a hydrothermal method. The results indicate that Nb doping into BNCBST induces lattice expansion and deepens dielectric relaxation. Moreover, the BNCBST‐xNb ceramics exhibit a great enhancement of electrical breakdown strength (Eb) with Nb content, which results from the reduction of grain size, the increase of resistivity, the decrease of oxygen vacancies, and the enlargement of band gap width. Consequently, the BNCBST‐0.15Nb system presents an outstanding Eb of 497 kV/cm with excellent recoverable energy density (Wrec = 3.85 J/cm3) and efficiency (η = 87.7%), accompanying by the wide temperature stability (Wrec and η vary within ± 9.8% and ± 1.4% at 40–100°C) and fast discharge rate (t0.9 = 88 ns). The significant improvement of Eb and energy storage properties suggest that our research offers an effective strategy for developing lead‐free energy storage ceramics.

Optimization in the energy storage properties of Bi0.5Na0.5TiO3–SrTiO3 ceramics by introducing Bi(Mg0.5Zr0.5)O3

AbstractAs one of the important electronic components, the dielectric capacitors for energy storage applications have been extensively studied in recent years. Among various dielectric materials, the perovskite oxide Bi0.5Na0.5TiO3‐based ceramics have become promising candidates due to their high polarization, dielectric tunability, environment‐friendly composition, and so forth. Herein, the relaxor ferroelectric ceramics of Bi0.5Na0.5TiO3–SrTiO3–Bi(Mg0.5Zr0.5)O3 were prepared via solid‐state reaction method. The sample with optimal composition not only retains the high polarization by introducing Bi3+ ions, but also achieves the reduced remanent polarization by enhancing relaxor behavior and the promoted electric breakdown strength by the grain size refinement. Accordingly, a high recoverable energy density of 8.3 J/cm3 under 450 kV/cm and the superb charge/discharge properties (current density CD = 1200 A/cm2, power density PD = 150 MW/cm3, charge/discharge time t0.9 = 0.15 µs) are achieved, revealing great prospect in energy storage applications.

Moderate electric field driven ultrahigh energy density in BiFeO3–BaTiO3–based ceramics with improved relaxor behavior and breakdown strength

Dielectric ceramic–based capacitors have triggered growing concerns because of their potential applications in next–generation pulsed power electronic devices. However, the low energy density seriously hampers their further development, and the high energy density (>6 J/cm3) is generally realized under a giant external electric field (>500 kV/cm). Herein, an ultrahigh recoverable energy density of 8.5 J/cm3 and a high efficiency of 87 % under a moderate electric field of 470 kV/cm is obtained in the Sr(Sc1/2Nb1/2)O3 modified BiFeO3–BaTiO3 ceramics via the improved dielectric relaxation and electric breakdown strength (Eb). And the promoted band gap and reduced grain size play a key role in enhancing Eb. Moreover, the sample with the optimal composition also exhibits superb thermal reliability at a wide temperature range, and outstanding frequency and cycling stability under 350 kV/cm. This work not only provides a hopeful alternative for advanced energy storage capacitors, but also demonstrates an effective way to explore high–performance dielectric materials.

Constructing a “micro-nano collaboration” network via disk-milling: Value-enhanced utilization of flexible temperature-resistant cellulose insulation films

Cellulose is a sustainable natural polymer material that has found widespread application in transformers and other power equipment because of its excellent electrical and mechanical performance. However, the utility of cellulose materials has been limited by the challenge of balancing heat resistance with flexibility. On the basis of the preliminary research conducted by the research team, further proposals have been put forward for a method involving disk milling to create a “micro–nanocollaboration” network for the fabrication of flexible, high-temperature-resistant, and ultrafine fiber-based cellulose insulating films. The resulting full-component cellulose films exhibited impressive properties, including high tensile strength (22 MPa), flexibility (92–263 mN), remarkable electrical breakdown strength (39 KV/mm), and volume resistivity that meets the standards for insulation materials (4.92 × 1011 Ω·m). These results demonstrate that the proposed method can produce full-component cellulose insulation films that offer both exceptional flexibility and high-temperature resistance.

Optimizing energy storage under low electric field in A-site dysprosium modified BiFeO3-BaTiO3 ceramics

Electric recoverable energy density and dielectric breakdown strength are crucial factors in the high power-density capacitors. This study highlights the A-site dysprosium (Dy) substituted perovskite 0.5(Bi1−xDyx)FeO3-0.5BaTiO3 relaxor ferroelectric ceramics (x = 0–0.30) in O2-atmosphere sintering. An overall pseudo-cubic structure with a major cubic Pm-3m symmetry was observed in all compositions accompanied by multiple lattice symmetries. Anti-polar orthorhombic Pbam space group and non-polar orthorhombic Pnma symmetry gradually increase while ferroelectric tetragonal P4mm symmetry decreases as Dy content approaches x = 0.3. Recoverable energy densities (Wrec) of 4.8 J/cm3 and 3.6 J/cm3, storing efficiencies (η) of 68% and 75%, and recoverable energy storage intensities (ρ) of ∼3.2×10−2 J/kV·cm2 and ∼2.1×10−2 J/kV·cm2 were attained at x = 0 and 0.10 at electric fields of 150 and 175 kV/cm, respectively. The breakdown strength is improved from 150 to 200 kV/cm as x increases from 0.0 to 0.30. This study suggests that grain boundaries and local nanoclusters may act as barriers to inhibit charge transport and consequently increase the breakdown strength.

Enhanced electrical and energy storage performances of Fe, Sb co-doped BNBCTS ceramics synthesized via the solid-state combustion technique

In this study BNBCTS ceramics were co-doped with Fe and Sb to form (Bi0.5Na0.5)0.93(Ba0.945Ca0.055)0.07(Ti(0.9946-x)Sn0.0054)(Fe0.5Sb0.5)xO3 ceramics (denoted as BNBCTS-xFS) with various x content and were prepared via the solid-state combustion technique to enhance the electrical and energy storage performance. The effect of co-doping Fe and Sb on the phase formation, defect dipole, microstructure, electrical and energy storage properties of BNBCTS-xFS ceramics was studied. When x content increased from 0.0 to 0.030, the amount of the rhombohedral (R) phase decreased from 51 to 24 % while the tetragonal (T) phase increased from 49 to 76 %. The increased Fe and Sb content increased the defect dipole of singly/doubly charged oxygen-vacancies (VO∙/ VO∙∙) and caused more Ti4+ to transition to Ti3+, which caused the transition temperature of the ferroelectric phase to relaxor state (TF-R) in the ceramics to drop to below room temperature and it exhibited relaxor characteristics at room temperature. The ceramic with an x content of 0.010 had the largest grain size (3.06 μm), excellence ferroelectric properties (Pr ∼31.04 μC/cm2, Pm ∼38.98 μC/cm2 and Ec ∼18.28 kV/cm), the largest electro strain (∼0.175 %) and a large d33* of 350 pm/V. Moreover, when x = 0.020, the ergodic relaxor ceramic showed the smallest grain size (1.03 μm), the lowest remanant polarization (Pr) of 4.52 μC/cm2 and the lowest coercive field (Ec) of 8.37 kV/cm, at an electric field of 60 kV/cm. More importantly, energy storage properties at the electric breakdown strength (Eb = 120 kV/cm) of the ceramics with an x content of 0.020 exhibited a recoverable energy storage density (Wrec) of 1.81 J/cm3, a total energy storage density (Wtotal) of 2.95 J/cm3 and an efficiency (η) of 61.30%, with excellent thermal (∼25–150 °C) and frequency stability (∼1–100 Hz). This study provides new insights into the modulation of BNBCTS ceramics with Fe and Sb co-doping, which could effectively improve the electrical properties and energy storage properties of BNBCTS-xFS ceramics.

Lightweight, low dielectric and heat-resistant polyimide fiber bulkpaper developed via alkali activated strategies for advanced insulation

With the prosperity of aviation, aerospace, and military equipment, critical requirements asked for insulating materials, which not only seek outstanding insulation, and low dielectric but also put particular emphasis on lightweight and heat resistance features. Herein, to enhance polyimide (PI) fibers bulkpaper, surface modification strategies were proposed and researched. Specifically, the hydrolysis effects of NaOH/DMAc and NaOH/H2O systems on PI fibers and PI fibers bulkpaper were investigated. The results indicated that the NaOH/DMAc system possessed more effective activation, which was proved by the contents of O elements and CO groups. Besides, the PI fibers bulkpaper derived from alkali-activated PI chopped fiber was developed through a wet-forming route, whose exhibited excellent performance with a density of 0.26 g/cm3, stress strength of 15.83 MPa, interlayer bonding strength of 293.47 J/m2, and electrical breakdown strength of 6.88 kV/mm. In addition, the bulkpaper exhibited low dielectric constant and dielectric loss of 1.37 and 0.0043 (at 106 Hz), respectively. The activation strategies provided a feasible path for advanced bulkpaper enhancement.

The ultra-high electric breakdown strength and superior energy storage properties of (Bi0.2Na0.2K0.2La0.2Sr0.2)TiO3 high-entropy ferroelectric thin films

The electric breakdown strength (Eb) is an important factor that determines the practical applications of dielectric materials in electrical energy storage and electronics. However, there is a tradeoff between Eb and the dielectric constant in the dielectrics, and Eb is typically lower than 10 MV/cm. In this work, ferroelectric thin film (Bi0.2Na0.2K0.2La0.2Sr0.2)TiO3 with a dielectric constant of 115 is found to exhibit an ultra-high Eb = 10.99 MV/cm, attributing to the high-entropy effects that could result in dense nanostructures with refined grains, low concentration of oxygen vacancies, low leakage current and small polar nano-regions in the thin film. A recoverable energy storage density of 5.88 J/cm3 with an excellent energy storage efficiency of 93% are obtained for the dielectric capacitor containing the thin-film dielectrics. Remarkably, the dielectric capacitor possesses a theoretical energy storage density of 615 J/cm3 compatible to those of electrochemical supercapacitors. The high-entropy ferroelectric thin films with ultra-high Eb and superior energy storage properties are much promising dielectrics used in next-generation energy storage devices and power electronics.

A polarization double-enhancement strategy to achieve super low energy consumption with ultra-high energy storage capacity in BCZT-based relaxor ferroelectrics.

Due to dielectric capacitors' already-obtained fast charge-discharge speed, research has been focused on improving their Wrec. Increasing the polarization and enhancing the voltage endurance are efficient ways to reach higher Wrec, however simultaneous modification still seems a paradox. For example, in the ferroelectric-to-relaxor ferroelectric (FE-to-RFE) phase transition strategy, which has been widely used in the latest decade, electric breakdown strength (Eb) and energy storage efficiency (η) always increase, while at the same time, the maximum polarization (Pmax) inevitably decreases. The solution to this problem can be obtained from another degree of freedom, like defect engineering. By incorporating Bi(Zn2/3Ta1/3)O3 (BZT) into the Ba0.15Ca0.85Zr0.1Ti0.9O3 (BCZT) lattice to form (1 - x)Ba0.15Ca0.85Zr0.1Ti0.9O3-xBi(Zn2/3Ta1/3)O3 (BCZT-xBZT) solid-solution ceramics, in this work, ultrahigh ferroelectric polarization was achieved in BCZT-0.15BZT, which is caused by the polarization double-enhancement, comprising the contribution of interfacial and dipole polarization. In addition, due to the electron compensation, a Schottky contact formed at the interface between the electrode and the ceramic, which in the meantime, enhanced its Eb. A Wrec of 8.03 J cm-3, which is the highest among the BCZT-based ceramics reported so far, with an extremely low energy consumption, was finally achieved. BCZT-0.15BZT also has relatively good polarization fatigue after long-term use, good energy storage frequency stability and thermal stability, as well as excellent discharge properties.

High energy storage of PbZrO3 antiferroelectric thin films via constructing phase composition

In this paper, we fabricated PbZrO3 (PZ) thin films by the way of sol–gel spin on LaNiO3 buffered SiO2/Si substrates, and annealed them at different given temperatures by rapid thermal annealing (RTA). By controlling annealing temperature, PZ thin films showed different microstructures and phase compositions, whose impact of electrical properties and energy storage performance were researched. According to the research findings, the phase composition of film presents a general rule with the decrease of annealing temperature: PZ thin films crystallize into perovskite phase, pyrochlore phase, and amorphous phase. The films annealed at 620 °C crystallized into a state of coexistence of pyrochlore phase and perovskite phases, which also show moderate recoverable energy density and the highest energy storage efficiency (8.7 J cm−3 and 93.1%). This energy storage performance can be attributed to the synergistic effect of high electric breakdown strength of dense pyrochlore phase structure and high maximum polarization of perovskite phase. The findings of this paper help to explain the influence of pyrochlore phase on the energy storge performance of thin films. Thus, it is useful way to improve the energy storage performance of thin films.

Achieving high energy storage performance in Na0.5Bi0.5TiO3‒based ceramics via Li+ substitution

In the search for dielectric material with high energy storage density, a ceramic system of 0.8Na0.5Bi0.5TiO3–0.2K1-xLixTaO3 (NBT-KLT-x, x = 0.1–0.5) is proposed in this work. The addition of Li2CO3 is conducive to the decrease of sintering temperature of ceramics. Moreover, the XRD diffraction data of sintered ceramics indicate that pure perovskite phase showing the pseudo-cubic structure can be achieved when x = 0.1–0.3 while the excessive addition of Li2CO3 leads to the formation of pyrochlore phase. Based on the Rietveld refinement and Raman results, the Li+ doping in the NBT-KLT-x solid solutions (x = 0.1–0.3) can improve the phase content of P4bm, induce the lattice expansion and structural change towards a higher-symmetry phase. TEM observation also demonstrates the reduction in the size of polar nanoregions. With increasing x from 0.1 to 0.5, both the oxygen vacancy concentration and grain size display a tendency to decrease first and then increase. For the x = 0.2 ceramics with the lowest oxygen vacancy concentration and grain size, the largest electrical breakdown strength and lowest polarization hysteresis are achieved, giving an excellent recoverable energy storage density of 4.86 J/cm3 under 32 kV/mm, accompanied by a high efficiency of 90.46 %. Additionally, the recoverable energy density achieves a high level of ∼3.5 J/cm3 and energy storage efficiency is larger than 80 % over 28–160 °C, suggesting the outstanding temperature stability.

High‐dielectric PVDF/MXene composite dielectric materials for energy storage preparation and performance study

AbstractPolyvinylidene fluoride (PVDF) has broad application prospects in the field of dielectric capacitors. However, the low dielectric constant of the polymer greatly limits the improvement of its energy storage density. In this paper, a highly conductive two‐dimensional transition metal carbide (MXene) is utilized to modify PVDF by doping to prepare PVDF/MXene composite dielectrics, and a PVDF/MXene model is established based on molecular dynamics simulations to investigate the microscopic mechanism of improvement in the dielectric properties of the PVDF matrix upon doping. Finally, the effect of the MXene on the thermal conductivity and the mechanical and insulating properties of PVDF was investigated. The experimental results show that the relative dielectric constant of the PVDF/MXene‐1.0 wt% system at 100 Hz reached 14.54, which is 55.96% higher than that of pure PVDF, and this doping amount or lower can reduce the dielectric loss of PVDF. In addition, MXene doping improved the mechanical and thermal properties of the composite material to a certain degree. When the doping amount of MXene was lower than 1.0 wt%, the electric breakdown strength of the composite system was maintained above 245 MV/m, which is sufficient to achieve good insulation strength under most conditions.Highlights The low dielectric constant of polymers limits the improvement of their energy storage density. The doping of polymers with small amounts of conductive fillers can effectively increase the dielectric constant of the polymer matrix. A two‐dimensional nanomaterial MXene is used to improve the dielectric properties of PVDF matrix and the micromechanisms are analyzed by molecular dynamics simulations. The key properties of PVDF/MXene, such as the mechanical properties, thermal conductivity and insulation, are characterized.

Epitaxial Stabilization of Perovskite ATeO3 Thin Films

Tellurium oxides of the ATeO3 form typically do not crystallize in perovskite structures. Here, we show that perovskite-like ATeO3 (A = Ca, Sr, Ba) thin films can be grown on perovskite single-crystal substrates via epitaxial stabilization. These films are stable with high optical bandgaps, low dielectric losses, and a high electric breakdown strength. Hysteretic dielectric behavior found in SrTeO3 and BaTeO3 strongly suggests the presence of antiferroelectricity and ferroelectricity, respectively. These properties make perovskite tellurium oxides possibly appealing candidates for thin film coating or insulator materials in advanced microelectronics. Tellurium oxides constitute a largely unexplored class of materials that might show new and interesting functionalities in epitaxial thin-films. Our work encourages new work within this field.

Improved dielectric temperature stability and energy storage properties of BNT-BKT-based lead-free ceramics

The lead-free ceramics (1-x)(0.84Bi0.5Na0.5TiO3-0.16Bi0.5K0.5TiO3)-xBiMg2/3Nb1/3O3 (denoted as (1-x)BNKT-xBMN) and (1-y)(0.85BNKT-0.15BMN)-ySr0.7La0.2TiO3 with y = 0.3 (denoted as BNKMN-0.3SLT) were prepared by means of a conventional solid state sintering method. Effects of introduction of BiMg2/3Ni1/3O3 and Sr0.7La0.2TiO3 on phase structure, microstructure, and dielectric, ferroelectric and energy storage properties of the ceramics were studied in detail. The ceramics (1-x)BNKT-xBMN show pure perovskite structure, while BNKMN-0.3SLT appears a secondary phase. All ceramics exhibit dense microstructures with mean grain sizes between 0.56 μm and 1.36 μm. The introduction of SLT into BNKMN causes obvious decrease in dielectric constant around Curie temperature, inducing the widest temperature window of 263 °C from 29 °C to 292 °C for TCC≤±15 %. The ceramic BNKMN-0.3SLT shows high electric breakdown strength (Eb ∼ 300 kV/cm), large maximum polarization (Pm ∼ 36.48 μC/cm2), and low remanent polarization (Pr ∼ 1.70 μC/cm2), inducing high energy storage density of 4.03 J/cm3 as well as high energy storage efficiency of 85.2 %.

Antiferroelectric nano-heterostructures filler for improving energy storage performance of PVDF-based composite films

Incorporating high permittivity inorganic ferroelectric in polymer dielectrics is the most prevalent and straightforward approach to improve their energy storage capacity, which has an extensive application prospect in power electronic circuits owing to their higher power density. However, the discharged energy density attained with these materials are mainly restrained by the high remnant electric displacement of ferroelectric and the large discrepancy in permittivity between inorganic and organic substance. Herein, we proposed a novel antiferroelectric (Pb0.875La0.05Sr0.05)(Zr0.595Sn0.4Ti0.005)O3@Al2O3 (PLSZST@AO) nano-heterostructure as fillers to fabricate nanocomposite films, wherein the Al2O3 layer with wide band gap and dielectric constant close to that of the PVDF matrix was encapsulated onto the antiferroelectric nanoparticle PLSZST to alleviate the discrepancy in permittivity and enhance the breakdown strength. Especially, the experimental results and computational simulations confirmed that the presence of Al2O3 layer is capable of effectively enhancing the electric displacement and breakdown strength, while reducing the remnant displacement and impeding the formation of electrical trees. As a result, the nanocomposite films exhibited an impressive discharged energy density of 18.2 J/cm3 along with a remarkably enhanced energy storage efficiency of 70 % near the high electrical breakdown strength of 594.7 MV/m when the fillers content was 3 wt%, which was far surpassed the pristine PVDF (Ud = 5.34 J/cm3 and η = 51.8 %). Together with its excellent mechanical strength, the monolayer film was verified to be an outstanding performance dielectric material, outperforming the current PVDF-based composite dielectrics for high-power energy storage capacitors. This work allowed for more versatility in designing and manufacturing flexibility nanocomposite films, which can contribute to improving their performance and practicality.