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We prepared sintered reaction‐bonded silicon nitride (Si3N4) ceramics using various amounts of yttria (Y2O3) and a fixed amount of magnesia as sintering additives and evaluated their effects on the microstructure and dielectric breakdown strength (DBS). The DBS tests were conducted at substrate thicknesses of approximately.3,.2,.1, and.05 mm for each sample. All the prepared samples exhibited a high relative density (> 98%) and were composed of grains of almost identical sizes and shapes. The DBS decreased as the amount of added Y2O3 increased, with the degree of decrease being more pronounced for the thinner substrates. In the case of substrates with the largest Y2O3 amount (5 mol%), the DBS decreased to the level observed for the thinnest substrate of.05 mm. The presence of yttrium ions around the grains increased the electrical conductivity of the glassy phase, resulting in a decreased DBS. Therefore, a smaller amount of Y2O3 led to a higher DBS. The observed decrease in the DBS (.05 mm) was attributed to the connection between the top and bottom surfaces of the substrate through a highly conductive path. [ABSTRACT FROM AUTHOR]

We prepared sintered reaction-bonded silicon nitride (Si 3 N 4) by using various lanthanide oxides and magnesia for sintering additives and evaluated their effects on the microstructure and dielectric breakdown strength (DBS). Both the microstructure and DBS varied by the types of the sintering additives, and artificial intelligence (AI) based determination was conducted for the DBS to separate the effect of microstructural factors from that of sintering additives. The results indicated that the DBS values varied mainly by the former effect. The microstructures of Si 3 N 4 with Eu 2 O 3 and La 2 O 3 contained a large number of pores, leading to lowered DBS; on the contrary, those with Tm 2 O 3 and Y 2 O 3 possessed dense microstructures with large-elongated grains, showing higher DBS. On the other hand, the Si 3 N 4 with Yb 2 O 3 showed lower DBS than what AI-determined from the microstructures because the additive forms grain boundary phase with a low electrical resistance. [ABSTRACT FROM AUTHOR]

Silicon nitride (Si 3 N 4) ceramics were prepared using various amounts of magnesia (MgO) and a fixed amount of yttria as sintering additives, and their effects on the microstructures and four essential properties were evaluated: bending strength, fracture toughness, thermal conductivity, and dielectric breakdown strength (DBS). The microstructure varied with the MgO content; a smaller amount promoted grain growth, while an excess amount formed pores. The properties varied along with these structural changes. It was revealed that the four properties coexist at a high level in the range of 4–7 mol% of MgO. In addition, the large amount of MgO enhanced the electric conductivity of grain boundary and decreased the DBS. It is speculated that tips of multigrain junctions composed of a sufficiently large amount of glass modifier might work as the severe defects for the dielectric breakdown. [ABSTRACT FROM AUTHOR]

In this work, we obviously enhanced the mechanical and dielectric insulation properties of the aramid nanofiber (ANF) film only by mixing a small amount of two-dimensional boron nitride nanosheets (BNNSs) (0.09 wt %), which were in situ introduced as the assistor of aramid splitting. The composite nanofilm exhibited a tensile stress of 282 MPa and a dielectric breakdown strength of 100.7 kV·mm–1, which increased by 55.8 and 149.3%, respectively. These improvements may be attributed to the introduction of BNNSs, which made the films denser and more horizontally ordered, as well as the enhanced interfacial interactions between individual ANFs. Meanwhile, the ANF/BNNS film also shows high thermal stability, self-extinguishing properties, and excellent chemical stability simultaneously. This work provides a strategy to enhance the mechanical and dielectric insulation properties of ANF-based nanocomposites. [ABSTRACT FROM AUTHOR]

This work deals with the synthesis, characterization of hybrid ethylene propylene diene monomer (EPDM) composites loaded with nano‐boron nitride (nano‐BN)/nano‐titanium dioxide (nano‐TiO2) and micro Mg(OH)2 particles for its suitability towards high‐voltage insulation application. The elastomer samples were prepared by carefully dispersing the micro and nano fillers during the mastication process of EPDM polymer using a two roll mill, followed by vulcanization. The samples were characterized for mechanical, morphological, thermal, and electrical insulation properties. The highest tensile strength among the composite samples was noted for 1 phr nanoparticles loaded samples. Fourier Transform Infrared (FTIR) results show no change in the chemical moiety upon addition of nano‐BN/nano‐TiO2 in EPDM composites. Enhancement in hydrophobicity is observed for 3 phr nano‐TiO2 loaded composites, which shows a maximum static contact angle of 110°. Meanwhile remarkable enhancement in the thermal conductivity and volume resistance of the composites are contributed to the addition of nano‐BN, thereby achieving maximum dielectric breakdown voltage (i.e., ~21 kV/mm for EMB3). Scanning electron microscope images and atomic force microscopy (AFM) topography highlight that low concentration (i.e., 1 phr) based composites have homogeneous dispersion in matrix and excessive nano filler addition deteriorates properties by forming filler aggregates and increasing surface roughness. [ABSTRACT FROM AUTHOR]

This study examines the function of Al2O3 nanofiller in liquid silicone rubber (LSR) for the purpose of outdoor insulation. Several characteristics, including structural (Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), physical (density), mechanical (tensile, tear, percentage elongation at break, and shore A hardness), thermal (thermal conductivity, thermo gravimetric analysis (TGA)), electrical (dielectric constant, dielectric breakdown strength, DC volume resistivity, arc resistance, and recovery of hydrophobicity), although chemical (immersion of samples for 72 h in NaCl, HCl, and H2SO4 solutions and measurement of sample weight and PH of the solution before and after immersion) were investigated after the addition of Al2O3 nanofiller with different compositions, such as 5, 10, and 15 weight percentages. In comparison to pure LSR, it was discovered that the inclusion of nano Al2O3 particles enhanced the material's density by 11%, thermal conductivity by 12%, dielectric constant by 24%, DC volume resistivity by 2%, arc resistance by significantly 1205%, dielectric breakdown strength by 54%, and hydrophobicity. Other improvements include a 7% rise in tensile strength, a 23% rise in tear strength, a 17% rise in hardness, and an 18% reduction in percentage elongation at break when compared to pure LSR for the composite samples. Mechanical qualities are affected by the curing process duration. More specifically, we discovered there is a proportionality relationship between the tensile strength and the elastic modulus. Findings of the chemical examination revealed that the composites have corrosion resistance in the form of negligible weight change in the sample when exposed to salt and acid solutions. The combination of these exceptional qualities makes Al2O3 composites appealing within an insulating materials realm. [ABSTRACT FROM AUTHOR]

Herein, a study on the dielectric properties of ZnO–P2O5–SeO2 glass ceramics containing varied contents of Ag2O is presented. Structural analysis of the samples by X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, Fourier transform infrared spectra, and optical absorption techniques indicated that the glasses are embedded with Ag3PO4, Ag2SeO3, and Zn3(PO4)2 anisotropic crystal phases along with Ag+ ions and Ag0 particles. Dielectric properties, ac conductivity (σac), and dielectric breakdown strength (DBS) are investigated as functions of Ag2O concentration. The results show the maximal concentration of Ag+ ions and Ag0 metallic particles in the sample containing 0.6 mol% of Ag2O. Dielectric parameters and (σac) increase with increasing Ag2O up to 0.6 mol%, while the DBS and electrical impedance decrease. The observed dipolar effects are quantitatively analyzed and possible dipoles are identified. Ionic contribution is predominant up to 0.6 mol% of Ag2O, beyond which the polaronic tunneling phenomenon prevails. These findings indicate that 0.6 mol% of Ag2O is the optimal concentration for using these glass ceramics as solid electrolytes in ionic batteries. Moreover, glass ceramics containing Ag2O beyond 0.6 mol% have exhibited larger polaronic conductivity, hence such glasses can be considered suitable candidates for electrodes in ionic batteries. [ABSTRACT FROM AUTHOR]

In this work, the neglected role of the dielectric breakdown strength (BDS) in piezoelectricity of bismuth layer-structured ferroelectrics (BLSFs) is revealed, enhanced initial polarization and BDS work together to improve the piezoelectricity of CaBi 4 Ti 4 O 15 (CBT) ceramics via Li/Bi co-substitution. The experimental work, first-principles calculations and finite element simulation are carried out to investigate the effect of Li/Bi co-substitution in depth. The stronger spontaneous polarization (P s) from the lattice distortion and the more favorable domain switching from the improved grain growth both contribute to an enhanced initial polarization. Besides, the changed grain-scale microstructure improves the hardness and inhibits the local discharge, the higher resistivity related to strong defect dipoles suppresses the heat generation during the poling process, all resulting in an increase of BDS by about 100%, and allowing more domains to align. This work demonstrates an effective strategy to develop BLSFs with enhanced piezoelectricity for high temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]

This paper reports on the influence of sintering additives CuO and MgO on the recently developed lead-free electrocaloric (EC) material Ba0.82Sr0.18Sn0.065Ti0.935O3 (BSSnT-18-6.5). Details on the sintering behavior and the resulting microstructure of bulk ceramic samples prepared through solid-state synthesis and their dielectric, ferroelectric, and electrocaloric properties are presented. On the one hand, the addition of CuO (xCuO = 2%) significantly reduced the sintering temperature from 1400 °C to 1150 °C. On the other hand, the addition of MgO (xMgO = 1%) dramatically reduced the average grain size from 40 µm to 0.4 µm, leading to an increase in dielectric breakdown strength from 4.4 V µm−1 to 7.7 V µm−1. Thus, BSSnT-18-6.5 with the addition of MgO to bulk ceramic samples could achieve maximum EC temperature changes (|ΔTEC|) of 0.27 K around 30 °C with almost no aberration within a broad temperature range from 5 °C to 50 °C under an applied electric field change of 5 V µm−1. The results show the potential of this material for the fabrication of multilayer ceramic (MLC) components for future electrocaloric applications. [ABSTRACT FROM AUTHOR]

Zinc selenium phosphate glasses added with the traces of Au2O3 were prepared and heat-treated. XRD, TEM, DSC, FT-IR and optical absorption (OA) spectroscopy methods were used for the structural assessment of these samples. Later, different dielectric parameters viz., dielectric constant (ε′), electric moduli (M), impedance (Z) and a.c. conductivity (σac) were measured over wide regions of frequency (ω) and temperature (T) as functions of Au2O3 concentration. Dielectric breakdown strength (DBS) of these samples was also measured at ambient conditions. The characterization studies indicated that multiple crystal grains were entrenched in the residual amorphous phase of the samples. The X-ray diffraction studies revealed that the bulk glasses consisted of Au2(SeO3)3 crystal phase and Au0 metallic particles (MPs). As Au2O3 content was raised, the intensity of the XRD peak related to Au3+ crystal phase indicated a growing trend, whereas that of Au0 MPs showed a decreasing trend. The results of XPS studies revealed similar inferences. The FT-IR results pointed out an improved degree of augmentation of the glass network as the content of Au2O3 was increased. Optical absorption (OA) - spectra of the glasses indicated a broad absorption band in the spectral range of 500–600 nm due to the surface plasmon resonance (SPR) of Au0 MPs. The intensity of the band was observed to decrease as Au2O3 content was increased and indicated decreasing proportion of Au0 metallic particles in the samples. The dielectric parameters exhibited a decreasing trend, whereas the dielectric breakdown strength (DBS) and electrical impedance indicated a substantial hike due to the increasing concentration of Au2O3. Overall, the presence of Au2O3 caused a significant improvement in the insulating strength of the ZnO added SeO2-P2O5 glasses and hence such glasses may be considered as insulating layers in the display panel devices. [ABSTRACT FROM AUTHOR]

Silicon nitride (Si3N4) was prepared from silicon by a sintered reaction‐bonded silicon nitride method using yttria and magnesia as sintering additives. Post‐sintering (PS) of nitrided compacts was carried out at 1850°C under a nitrogen pressure of 1 MPa. Effect of PS time on microstructure and dielectric breakdown strength (DBS) of the prepared Si3N4 ceramics was evaluated. The DBS was measured using specimens with four different thicknesses (0.30, 0.20, 0.10, and 0.05 mm) in order to examine the thickness dependence. The porosity of the sintered Si3N4 decreased by prolonging the PS time, and the full density could be achieved at the PS time of over 6 h. After full densification, rod‐like β‐Si3N4 grains grew up, and their maximum grain size increased from 45.1 to 154.7 μm by prolonging the PS time from 6 to 48 h. The DBS of the thick Si3N4 substrates (0.30 mm) showed little variation from 35.4 to 47.0 kV/mm, regardless of the PS time. On the other hand, that of the thin ones (0.05 mm) dramatically decreased from 99.5 to 9.8 kV/mm with increased the PS time from 6 to 48 h. Because the DBS sharply decreased at the thin substrate sintered for longer time in which some large‐elongated grains might span the substrate thickness‐wise throughout, it was inferred that the interface between β‐Si3N4 grains and grain boundary phase/intergranular glassy films might be a path of the dielectric breakdown. [ABSTRACT FROM AUTHOR]

Polar group-modified crosslinked polyethylene (XLPE) materials are developed with a peroxide thermochemical method of individually grafting chloroacetic acid allyl ester (CAAE) and maleic anhydride (MAH) to polyethylene molecular-chains, which are dedicated to ameliorating dielectric characteristics through charge-trapping mechanism. By free radical addition reactions, the CAAE and MAH molecules are successfully grafted to polyethylene molecular chains of XLPE in crosslinking process, as verified by infrared spectroscopy molecular characterizations. Dielectric spectra, electric conductance, and dielectric breakdown strength are tested to evaluate the improved dielectric performances. Charge trap characteristics are investigated by analyzing thermal stimulation depolarization currents in combination with first-principles electronic-structure calculations to reveal the polar-group introduced mechanisms of contributing dipole dielectric polarization, impeding electric conduction, and promoting electrical breakdown field. The grafted polar-group molecules, especially for MAH, can introduce deep-level charge traps in XLPE materials to effectively restrict charge injections and hinder charge carrier transports, which accounts for the significant improvements in electric resistance and dielectric breakdown strength. [ABSTRACT FROM AUTHOR]

Herein, the breakdown mechanism of alumina‐based ceramics (Al2O3–ZrO2) is studied. The specimens are characterized for their density, phase structure, micromorphology, breakdown process, and breakdown channel by micro computed tomography, high‐speed cameras, etc. The study reveals that the dielectric breakdown stability of the samples shows a decreasing trend and the dielectric loss shows an upward trend with the increase of ZrO2 content. The tetragonal phase zirconia is beneficial to enhance the dielectric breakdown strength of the sample, which is related to the martensitic transformation to prevent crack propagation. Before the ceramic breakdown, the insulating oil first breaks down, causing electric sparks. Once the ceramic breakdown occurs, the charges are rearranged, and a large amount of heat energy is generated instantly to melt the substance around the breakdown channel and erupt to the surface to form pits under the action of high internal stress. [ABSTRACT FROM AUTHOR]

In order to improve electrical matching between ethylene-propylene-diene misch-polymere (EPDM) reinforce insulation and crosslinked polyethylene (XLPE) main insulation in direct current (DC) cable accessories, the glyceryl monooleate (GMO) organic compound composed of several polar-groups and one long carbon chain is employed for chemical graft modification on EPDM to ameliorate DC electrical performances. Charge trap characteristics are analyzed by testing thermal stimulation current (TSC) and verified by calculating first-principles electronic properties to elucidate the GMO-graft-modified charge trapping mechanism accounting for DC electric conductance and dielectric breakdown. The grafted GMO molecules introduce substantial shallow charge traps that lead to nonlinear profiles of electric conduction versus electric field and cause hopping transports of percolation conductance. Electric conductance of EPDM is significantly improved by GMO graft for electrical matching with XLPE, while a high level of dielectric breakdown strength is retained sufficiently for reinforce insulation in cable accessories. Shallow charge traps introduced by GMO graft are capable of capturing charge carriers to form homocharge layers near electrodes which can scatter the transporting charge carriers and exclude further charge injections, thus to mitigate the dielectric breakdown strength reduction caused by electric conductivity improvement. Electric field finite-element simulations demonstrate that the electric field in DC cable terminals can be evidently homogenized by using GMO-grafted EPDM as reinforce insulation. [ABSTRACT FROM AUTHOR]

Succinct evaluation of dielectric breakdown strength of dielectric materials has been hampered by extrinsic parameters like size/thickness dependence, electrode configuration, and defect concentration which all mask the materials' intrinsic value. A novel indentation method to prepare arch-shaped indents on the surface of BaTiO 3 green stacks has been developed to overcome this problem. Utilizing this method enables simple and reliable sample preparation for investigation of dielectric breakdown behavior. Theoretical and experimental investigations reveal vanishing electrode edge effects governed by the improved distribution of electric field due to the arch-shaped indents. Thus, the novel indentation method bears advantages compared to measuring DBS of disk-shaped samples and allows for narrowing influences of extrinsic parameters. By obtaining breakdown channels close to the center of the indent, this technique additionally features the possibility of localizing the breakdown event. [ABSTRACT FROM AUTHOR]

Thin films of 3-methacryloyloxypropylheptaisobutyl-T8-silsesquioxane (BuPOSSMA) were prepared by an electron-assisted (e-assist) deposition method. The film deposited by the conventional vapor deposition without the e-assist had a polycrystalline structure with a rough surface, whereas the e-assist deposition produced amorphous polymer thin films with a smooth surface. The deposited films were electrically insulating with a breakdown strength higher than 2 × 106 V cm−1. The polymerization of BuPOSSMA resulted in a decrease in the dielectric constant of the film. It was found that the deposition-polymerization achieved by the e-assist is effective in improving the thermal stability of the insulating and dielectric characteristics. [ABSTRACT FROM AUTHOR]

Transparent energy storage ceramics can balance energy storage characteristic and optical characteristic, and are expected to be used in areas such as transparent pulse capacitors. However, excellent energy storage performance and dramatic light transmittance are difficult to achieve simultaneously, limiting their subsequent development in the actual applications. The paper proposes a way to improve the transparent energy storage properties of KNN-based samples by regulating domain and grain size. By introducing an appropriate amount of Er 2 O 3 , fine cube grains and nanodomains are constructed. When doping 0.20 mol% Er 2 O 3 , the ceramics exhibited excellent recoverable energy storage density W rec ∼ 6.2 J/cm3, superior energy-storage efficiency η ∼ 71.3 %, large dielectric breakdown strength E b ∼ 670 kV/cm, ultrahigh hardness value of 6.9 GPa, and a maximum transmittance T ∼72 % at 880 nm. Dense microstructure, nanoscale grains, symmetrical lattice structure and relaxor behavior are the main reasons for obtaining high energy storage and transparency properties. • The W rec and η of x =0.20 sample are improved synergistically. • The energy storage property and light transmittance are improved synergistically. • The x =0.20 sample has excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Lead-free ceramic-based dielectric capacitors show huge potential in electrical energy storage in pulsed power systems due to their fast charge/discharge rate, ultrahigh power density and environmental friendliness. However, unsatisfied charge/discharge performance characterized by inferior recoverable energy storage density (W rec generally <5 J/cm3) has become a key bottleneck to restrict their applications in cutting-edge energy storage devices. In this paper, we focus on simultaneously realizing ultrahigh W rec and efficiency (ƞ) in eco-friendly Bi 0.5 Na 0.5 TiO 3 (BNT)-based dielectric ceramics via chemical doping. Interestingly, highly dynamic polar nanoregions (PNRs) and nanodomains are constructed by incorporating Sr 0.7 Nd 0.2 TiO 3 (SNT) into 0.94BNT-0.06BaTiO 3. Of great importance, the resulting relaxor ferroelectrics (RFEs) exhibit high bulk resistivity, submicron grain size and wide band gap due to high level of SNT doping accompanying with 1 at% Nb donor doping. Therefore, excellent energy storage properties with ultrahigh W rec ∼8.08 J/cm3 and ƞ ∼92.1% are achieved due to coexistence of large polarization difference (Δ P = P max − P r) and giant dielectric breakdown electric field (E b ∼540 kV/cm). Furthermore, excellent temperature / frequency/cycling stability characterized by Δ W rec < ±4% and Δ η < ±2% ensure the energy storage applications of the studied dielectric ceramics over an enormous range of scales. [Display omitted] • Energy storage performance of 0.96BNT-0.06BT ceramic is remarkably improved by SNT and Nb co-doping. • Ultrahigh W rec ∼8.08 J/cm3 and ƞ ∼92.1% are simultaneously realized due to existence of large Δ P and giant E b. • Excellent temperature/frequency/cycling stability are characterized by Δ W rec <+4% and Δ η <+2% • The present paper provides a strategy to design advanced high/pulsed power dielectric capacitors. [ABSTRACT FROM AUTHOR]

This paper reports on the influence of sintering additives CuO and MgO on the recently developed lead-free electrocaloric (EC) material Ba0.82Sr0.18Sn0.065Ti0.935O3 (BSSnT-18-6.5). Details on the sintering behavior and the resulting microstructure of bulk ceramic samples prepared through solid-state synthesis and their dielectric, ferroelectric, and electrocaloric properties are presented. On the one hand, the addition of CuO (xCuO = 2%) significantly reduced the sintering temperature from 1400 °C to 1150 °C. On the other hand, the addition of MgO (xMgO = 1%) dramatically reduced the average grain size from 40 µm to 0.4 µm, leading to an increase in dielectric breakdown strength from 4.4 V µm−1 to 7.7 V µm−1. Thus, BSSnT-18-6.5 with the addition of MgO to bulk ceramic samples could achieve maximum EC temperature changes (|ΔTEC|) of 0.27 K around 30 °C with almost no aberration within a broad temperature range from 5 °C to 50 °C under an applied electric field change of 5 V µm−1. The results show the potential of this material for the fabrication of multilayer ceramic (MLC) components for future electrocaloric applications.

Featured Application: Molten metal filter and ceramic membrane. In recent years, there has been growing interest in porous ceramics in many research areas given their superior thermal and chemical resistance capabilities, unlike porous metals and porous polymers. Among the various types of porous ceramics, reticulated porous ceramics can offer significant industrial potential due to the low density and high permeability of these materials. However, industrial applications are somewhat rare owing to the rather low compressive strength of reticulated porous ceramics compared to other types of porous ceramics. Although there have been many studies related to reticulated porous ceramics, few have focused on reticulated porous zirconia. Therefore, the aim of this study is to determine how to obtain a high compressive strength in reticulated porous zirconia by optimizing the process conditions of the solid loading level and the particle size and by using additives in a zirconia slurry sample. Furthermore, the authors assess the effects on the microstructure and compressive strength of multiple slurry coating, specifically from one to three. In conclusion, the effect of varying these various process conditions on the resulting improvement in compression strength was investigated, and the compression strength of reticulated porous zirconia was significantly increased from 0.14 to 9.43 MPa. The characteristics investigated include the pore characteristics (pore density, pore size and pore structure), the sintering behavior (linear shrinkage), the mechanical properties (compressive strength), and the dielectric properties (dielectric breakdown strength). [ABSTRACT FROM AUTHOR]

The use of porcelain and thermoplastic based materials as High voltage insulators has always been dominant in the industry. Several elastomers were also investigated, mainly Ethylene Propylene Rubber and Silicone rubbers were used as replacement of the traditional Porcelain high Voltage insulators. In this study we experiment with new elastomer, Ethylene propylene diene rubber (EPDM), that is capable of withstanding high voltage as well as being resistant to severe weathering conditions. In addition to having excellent mechanical properties that we discussed elsewhere. Detailed dielectric breakdown measurements were carried out for room temperature vulcanized and high temperature vulcanized samples. The effects of exposure to UV radiation on the dielectric breakdown strength was also studied. Different fillers were used to improve the dielectric breakdown strength of different polymer matrices. Both carbon black based fillers and inorganic fillers were experimented in order to reach optimum mix properties that provide the best dielectric breakdown strength. Resistance to thermal aging and UV radiation was also carried out on EPDM samples. [ABSTRACT FROM AUTHOR]

A large number of insulation/dielectric failures in power systems are related to thermally-induced dielectrical breakdown, also known as ‘thermal breakdown’, at higher operating temperatures. In this work, the thermal breakdown behavior of typical silicone formulations, used as dielectrics in stretchable electronic devices, is analyzed at practically relevant operating temperatures ranging from 20°C to 80°C. An effective way of delaying the thermal breakdown of insulating materials is to blend micro- or nano-sized inorganic particles with high thermal conductivity, to dissipate better any losses generated during energy transduction. Therefore, two types of commercial silicone formulations, blended with two types of rutile hydrophobic, high-dielectric TiO2 fillers, are investigated in relation to their dielectric properties, namely, relative permittivity, the dissipation factor, and electrical breakdown strength. The breakdown strengths of these silicone composites are subsequently evaluated using Weibull analysis, which indicates a negative correlation between temperature and shape parameter for all compositions, thus illustrating that the homogeneity of the samples decreases in line with temperature, but the breakdown strengths nevertheless increase initially due to the trapping effect from the high-permittivity fillers.

In this work, heat treatment was performed on three retired 110 kV AC cables with service years of 0, 15 and 30, and the effects on the thermal and electrical performance of the cable insulation were investigated. First, each cable with a length approximately of 5 m was prepared and cut into five equal segments. Four segments of each cable were annealed at a temperature of 90, 95, 100, or 105 °C by building a small circuit to simulate cable operation. Then, a section at the middle of each segment was cut out, and the insulation layer was peeled away. The peeled-off layers from the inner, middle and outer positions were selected as the test samples. Subsequently, Fourier transform infrared spectrometry (FTIR), and differential scanning calorimetry (DSC) were performed, and the DC conduction current and dielectric breakdown strength were measured. The best thermal properties of the highest melting point, crystallinity, and smallest melting range were found when the cables were annealed at 100, 105, and 105 °C for the inner, middle, and outer positions, respectively. The highest dielectric breakdown strength and lowest electrical conductivity were found at temperatures of 95 or 100 °C for the inner and middle positions, respectively, and at 105 °C for the outer position. The FTIR results showed that thermal annealing for hundreds of hours did not adversely affect the molecular chains. It is found that this type of heat treatment could be a feasible method to rejuvenate retired cables, and a conservative temperature of 95 °C is regarded as the optimum annealing temperature.

Further research on retired cable rejuvenation via heat treatment was investigated in this paper. Three retired cables with service year of 7, 15 and 30 years were used and annealed at different temperatures following two different heat treatment methods. In the first test, two short cables with a length of 5 m were prepared and cut into five equal segments. Four segments of each cable were annealed at 90, 95, 100, and 105 °C to simulate the cable operation. Then, the cross-linked polyethylene (XLPE) from the cable insulation was peeled, and the peels from the inner, middle and outer positions were selected and subjected to the differential scanning calorimetry (DSC), DC conduction current, and dielectric breakdown strength measurements. The thermal and electrical performance of these samples were analyzed, and the optimum annealing temperature was determined. In the second test, three identical long cables were connected to a transformer, joints, and terminals to build two experimental circuits. The cables were annealed at the optimum temperature determined in the first test. The same measurements were performed on XLPE samples taken from the same positions as those in the first test. The results showed that the short cables exhibited the best thermal and electrical performance when annealed at 95 °C. The three long cables annealed at 95 °C verified that the thermal and electrical properties of the cable insulation were significantly improved. The results of the two different annealing methods, which closely represent the actual cable operations, verified the feasibility that old cables without overheating history could be rejuvenated via heat treatment.

Polar group-modified crosslinked polyethylene (XLPE) materials are developed with a peroxide thermochemical method of individually grafting chloroacetic acid allyl ester (CAAE) and maleic anhydride (MAH) to polyethylene molecular-chains, which are dedicated to ameliorating dielectric characteristics through charge-trapping mechanism. By free radical addition reactions, the CAAE and MAH molecules are successfully grafted to polyethylene molecular chains of XLPE in crosslinking process, as verified by infrared spectroscopy molecular characterizations. Dielectric spectra, electric conductance, and dielectric breakdown strength are tested to evaluate the improved dielectric performances. Charge trap characteristics are investigated by analyzing thermal stimulation depolarization currents in combination with first-principles electronic-structure calculations to reveal the polar-group introduced mechanisms of contributing dipole dielectric polarization, impeding electric conduction, and promoting electrical breakdown field. The grafted polar-group molecules, especially for MAH, can introduce deep-level charge traps in XLPE materials to effectively restrict charge injections and hinder charge carrier transports, which accounts for the significant improvements in electric resistance and dielectric breakdown strength.

In order to improve electrical matching between ethylene-propylene-diene misch-polymere (EPDM) reinforce insulation and crosslinked polyethylene (XLPE) main insulation in direct current (DC) cable accessories, the glyceryl monooleate (GMO) organic compound composed of several polar-groups and one long carbon chain is employed for chemical graft modification on EPDM to ameliorate DC electrical performances. Charge trap characteristics are analyzed by testing thermal stimulation current (TSC) and verified by calculating first-principles electronic properties to elucidate the GMO-graft-modified charge trapping mechanism accounting for DC electric conductance and dielectric breakdown. The grafted GMO molecules introduce substantial shallow charge traps that lead to nonlinear profiles of electric conduction versus electric field and cause hopping transports of percolation conductance. Electric conductance of EPDM is significantly improved by GMO graft for electrical matching with XLPE, while a high level of dielectric breakdown strength is retained sufficiently for reinforce insulation in cable accessories. Shallow charge traps introduced by GMO graft are capable of capturing charge carriers to form homocharge layers near electrodes which can scatter the transporting charge carriers and exclude further charge injections, thus to mitigate the dielectric breakdown strength reduction caused by electric conductivity improvement. Electric field finite-element simulations demonstrate that the electric field in DC cable terminals can be evidently homogenized by using GMO-grafted EPDM as reinforce insulation.

In this paper, the performance of several annealing methods on three retired cables and the annealing effects on the improvement in the thermal and electrical properties of cross-linked polyethylene (XLPE) insulation were discussed. The cable insulation layer was peeled, and the peels near the inner semi-conductive layer were used as the test samples. Isothermal treatment and heat recycling treatment were performed at temperatures of 85, 90, 95, and 100 °C, and the temperatures were held in the heat recycling treatment for 8, 16, and 24 h, respectively. Each heat recycling treatment was repeated 20 times, and the duration of the isothermal treatment was the same as that for the heat recycling treatment with a 24 h temperature holding hour. Then, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were performed, and the dielectric spectrum, DC conduction current, and dielectric breakdown strength EB were measured. The results showed that damage involving molecular changes is linearly related to the cable service year. As the annealing temperature increases, the melting range and electrical conductivity decrease; the melting point, crystallinity, lamellar thickness, and dielectric breakdown strength increase; and the optimal values appear for the samples annealed at 95 °C. With an increased temperature holding hour, the peels annealed at 95 °C exhibit a decreased melting range and electrical conductivity and an increased crystallinity, melting point, lamellar thickness, and dielectric breakdown strength. As a result, the two different treatments are verified to effectively improve the thermal and electrical properties for the XLPE as early research on cable rejuvenation by heat treatment.

Dielectric elastomer actuators (DEAs) are promising soft electromechanical transducers for soft robotics. Fabricating a high‐performance DEA actuated by sub‐kV voltage remains challenging. Here, a facile method not only to fabricate ultrathin dielectric elastomer films of triblock copolymers but also to enhance the dielectric breakdown strength and thus enhance the electromechanical performance is reported. A thick thermoplastic elastomer film of poly(styrene‐b‐butyl acrylate‐b‐styrene) from solution blading is symmetrically pre‐stretched and relaxed at 120 °C to fabricate a freestanding ultrathin DE film. Compared with the pristine DE film of the same thickness (12 µm), the thermally‐relaxed DE film with equally biaxial pre‐stretch ratio 3.5 × 3.5 exhibits increased electrical breakdown strength by a factor of 1.9 (from 43 to 82 V µm−1), maximum actuation area strain by a factor of 1.9 (from 11.7% to 22.4%), and highest energy density by a factor of 5.7 (from 4.5 to 25.8 kJ m−3). The enhancement may be ascribed to the self‐reinforcement of the dielectric breakdown strength due to the morphology change of polystyrene nanodomains from spheres to oblate spheroids. Thanks to the ultra‐thinness, the high electromechanical performance is achieved within sub‐kV driving voltage in all cases. [ABSTRACT FROM AUTHOR]

The dielectric breakdown strength of borosilicate glass and alumina was measured as a function of the voltage ramp rate on different material thicknesses and with different electrode configurations. While this is not a completely new approach, with our work we want to highlight the importance of appropriate measurement set-up and contribute to a better understanding and analysis of dielectric breakdown. The measurement of breakdown tests is generally anything but trivial and the comparison of breakdown results for different set-ups is difficult, especially because not all scientific articles go into detail on the measurement method and all the important parameters, which can influence the breakdown event. For the results shown in this work we mainly used glass as a suitable model material and two different electrode setups at eleven different voltage ramps in the range of 5 V/s to 10,000 V/s. We found that there is a clear dependence of the dielectric breakdown strength on the voltage ramp and the electrode configuration as well as it should be distinguished between breakdowns which initiated at electrode edge and those initiated within the electrode area. There is almost no scatter for breakdown strengths which were initiated inside a silver paste electrode in comparison to breakdown strength from the electrode edges. [ABSTRACT FROM AUTHOR]

• Ca 1-1.5 x Sm x □ 0.5 x TiO 3 ceramics designed in terms of A-site donor Sm3+ and A-site vacancy (V A) were prepared by a solid state reaction method. • A-site donor Sm3+ and A-site vacancy (V A) strategy results in the greatly enhanced dielectric breakdown strength. • Ca 1-1.5 x Sm x □ 0.5 x TiO 3 ceramics present the linear dielectric feature with significantly decreased dielectric loss. • High energy storage density (U = 2.0 J/cm3) and energy efficiency (η = 93.7 %) are achieved. Ceramic-based capacitors for energy storage devices require simultaneously high energy density and efficiency. Achieving high electric breakdown field based on linear dielectrics is crucial. Here, A-site Sm3+ doped perovskite Ca 1-1.5 x Sm x □ 0.5 x TiO 3 ceramics with introduced A-site vacancies (V A) were prepared. All Ca 1-1.5 x Sm x □ 0.5 x TiO 3 ceramics crystallize in an orthorhombic structure, with lattice constants a , b , and c linearly decreased. As a result of Sm3+ dopants and V A , the grain size decreased while the ceramics' density was improved. The permittivity decreases from 176 (x = 0) to 135 (x = 0.1), but tan δ is effectively constrained (∼10−4). What's more, the dielectric breakdown strength is significantly improved from 429 kV/cm (x = 0) to 547 kV/cm (x = 0.1) with dielectric linearity is maintained. The optimum energy storage density of 2 J/cm3 (x = 0.02) with ultrahigh energy efficiency of over 93.7 % is achieved, which are superior to many existing linear dielectrics and relaxor ferroelectrics. This work confirms the energy-storage enhancement through chemical modifications and microstructural engineering. [ABSTRACT FROM AUTHOR]

In recent years, there has been growing interest in porous ceramics in many research areas given their superior thermal and chemical resistance capabilities, unlike porous metals and porous polymers. Among the various types of porous ceramics, reticulated porous ceramics can offer significant industrial potential due to the low density and high permeability of these materials. However, industrial applications are somewhat rare owing to the rather low compressive strength of reticulated porous ceramics compared to other types of porous ceramics. Although there have been many studies related to reticulated porous ceramics, few have focused on reticulated porous zirconia. Therefore, the aim of this study is to determine how to obtain a high compressive strength in reticulated porous zirconia by optimizing the process conditions of the solid loading level and the particle size and by using additives in a zirconia slurry sample. Furthermore, the authors assess the effects on the microstructure and compressive strength of multiple slurry coating, specifically from one to three. In conclusion, the effect of varying these various process conditions on the resulting improvement in compression strength was investigated, and the compression strength of reticulated porous zirconia was significantly increased from 0.14 to 9.43 MPa. The characteristics investigated include the pore characteristics (pore density, pore size and pore structure), the sintering behavior (linear shrinkage), the mechanical properties (compressive strength), and the dielectric properties (dielectric breakdown strength).

Discovering new materials with high breakdown strength is of great significance for scientific research and industrial applications. Here, we combine experiments and density functional theory (DFT) calculations to report a systematic study of two titanosilicates - A 2 TiSi 2 O 8 (A = Br, Sr) as a family of functional materials with wide band gaps, ultrahigh breakdown strength, and high thermal stability. The A 2 TiSi 2 O 8 materials possess ultrahigh electric breakdown (E b > 200 kVmm−1, at 200 ℃), and good temperature stability (the variation of capacitance 3 %, from −100 to 200 ℃). DFT results show that electrons are likely localized in the Si O and Ti O polyhedrons. The electron difference density map and density of states (DOS) results elucidate the wide band gaps in titanosilicate family due to the strong Si O and Ti O bonds, indicating that the semiconductive behaviors are similar. The temperature-dependent structural evolution (from −100 to 500 ℃) is investigated via in-situ Raman spectroscopy. [ABSTRACT FROM AUTHOR]

A large number of insulation/dielectric failures in power systems are related to thermally-induced dielectrical breakdown, also known as 'thermal breakdown', at higher operating temperatures. In this work, the thermal breakdown behavior of typical silicone formulations, used as dielectrics in stretchable electronic devices, is analyzed at practically relevant operating temperatures ranging from 20°C to 80°C. An effective way of delaying the thermal breakdown of insulating materials is to blend micro- or nano-sized inorganic particles with high thermal conductivity, to dissipate better any losses generated during energy transduction. Therefore, two types of commercial silicone formulations, blended with two types of rutile hydrophobic, high-dielectric TiO2 fillers, are investigated in relation to their dielectric properties, namely, relative permittivity, the dissipation factor, and electrical breakdown strength. The breakdown strengths of these silicone composites are subsequently evaluated using Weibull analysis, which indicates a negative correlation between temperature and shape parameter for all compositions, thus illustrating that the homogeneity of the samples decreases in line with temperature, but the breakdown strengths nevertheless increase initially due to the trapping effect from the high-permittivity fillers. [ABSTRACT FROM AUTHOR]

• The introduction of Ca inhibits the grain growth and reduces oxygen vacancies. • The optimal composition exhibits ultra-high dielectric breakdown strength. • The optimal composition exhibits ultra-high energy storage density and efficiency. • The optimal composition shows excellent stability of temperature and frequency. • The optimal composition exhibits high power density. Sr 0.7 Bi 0.2 TiO 3 with high relaxor behavior and energy storage efficiency (η) is expected to be applied in power energy storage capacitors. However, its energy storage density is limited by the relatively low dielectric breakdown strength (DBS). Herein, Sr 0.7 Bi 0.2 Ca x TiO 3 (SBT-xC, x = 0 ∼ 0.15) was prepared to decrease the average grain size of Sr 0.7 Bi 0.2 TiO 3. This can effectively eliminate the oxygen vacancy and decrease the electrical conductivity and leakage current, which result in the enhanced DBS. Meanwhile, Ca doping increases the relaxor behavior and dielectric constant. When x = 0.1, the composition exhibits high DBS of 480.2 kV/cm and excellent energy storage properties, such as high energy storage density of 2.1 J/cm3 with high η of 97.6 % at 290 kV/cm, considerable thermal stability and great frequency stability. Moreover, SBT-0.1C shows high power density of 50.1 MW/cm3. These results suggest that SBT-0.1C is a potential candidate for high performance dielectric energy storage applications. [ABSTRACT FROM AUTHOR]

In this work, a new (Sr 0.7 Ba 0.3) 5 LaNb 7 Ti 3 O 30 system ceramic with a filled tetragonal tungsten bronze structure was proposed and fabricated by the traditional solid phase method. Crystal structure, relaxor behaviors and energy storage capabilities were studied. Large relaxor activation energy indicates a "weakly coupled relaxor" mechanism, which is advantageous for obtaining better energy storage performance, and lower conductance activation energy can further prove the formation of the filled tungsten bronze structure. More importantly, a dielectric breakdown strength of up to 35.5 kV/mm was obtained. The releasable energy density and efficiency at 24 kV/mm are 1.36J/cm3 and 91.9%, respectively. In addition, due to the high current density and high dielectric breakdown strength, a current density of 477.5 A/cm2 and a power density of 42.9 MW/cm3 are achieved, meaning that SBLNT ceramic is a potential candidate dielectric ceramic for energy storage. [ABSTRACT FROM AUTHOR]

To extend the cable service life, the feasibility of cable rejuvenation on two retired cables through heat treatment was investigated in this study. First, two retired 110 kV AC cables without overheated record were annealed at four temperatures of 90, 95, 100, and 105 °C by simulating the cable operation. Second, the insulation layer of the annealed cables was peeled, and the peels near the inner conductor were selected as test samples. Then, differential scanning calorimetry was performed, and the DC conduction current and dielectric breakdown strength E B were measured. The results showed that the heat treatment of simulating cable operation could be a feasible method to rejuvenate retired cables and 95 °C was determined to be the optimum annealing temperature for the two cables. [ABSTRACT FROM AUTHOR]

In recent years, porous ceramics have been increasingly developed owing to their high levels of high-temperature stability and chemical stability. These properties are far superior to porous polymers and porous metals. As a representative porous ceramic, reticulated porous ceramics have been fabricated for several decades owing to their overwhelmingly high porosity, which is usually above 90%. There are growing concerns about the environmental problems. However, the data on the preparation of low-cost and natural material-based reticulated porous ceramics are not enough. Therefore, the authors studied the preparations and characterizations of reticulated porous ceramics prepared using diatomite and kaolin, and compared them to typical reticulated porous alumina. The obtained data were used to determine whether the reticulated porous diatomite-kaolin composite can be practically used in non-hard loading conditions. The structural properties and dielectric breakdown strength of the reticulated porous ceramics were examined using scanning electron microscopy, mercury porosimetry, μ-computed tomography (CT), and standard test apparatus of dielectric breakdown voltage. [ABSTRACT FROM AUTHOR]

Tetragonal PBLZST antiferroelectric ceramics is the most studied energy storage material because of its unique double hysteresis loops. However, the dielectric breakdown strength of PBLZST is relatively low, which severely restricts to acquire high energy storage density. In this paper, the PBLZST: x MgO ceramics are synthesized by a two-step calcining method. High-temperature calcination of PBLZST can reduce its activity and inhibit the diffusion between PBLZST and MgO. By regulating the amount of MgO, the influence on the microstructure and properties of PBLZST are systematically researched. As the amount of MgO increases from 0 to 0.2 wt%, the dielectric breakdown strength enhances from 175.2 to 265.2 kV/cm. The PBLZST: x MgO ceramics reach its highest recoverable energy density (5.02 J/cm3) at x = 0.1 wt%. And, its energy storage density only changes by 15.7% with the temperature ranging from 25 to 120 °C. Results prove that introducing MgO into PBLZST with a two-step calcining method can effectively enhance the dielectric breakdown strength. [ABSTRACT FROM AUTHOR]

Linear dielectric ceramics have received much attention due to high power density, fast discharge speed and ultralow dielectric loss, which are expected as promising candidates for the pulsed power system applications. However, their relatively low dielectric breakdown strength usually cannot meet the requirements of practical application. In this work, we adopt hot-press sintering method to enhance the dielectric breakdown strength of the TiO 2 -SiO 2 -Al 2 O 3 based ceramics, and the dielectric breakdown strength reaches 77.5 kV/mm, which is 1.8 times as large as samples prepared by conventional sintering method. The effect of different sintering methods on microstructure, dielectric properties and dielectric breakdown strength is investigated. The improvement of dielectric breakdown strength can be ascribed to improved bulk density, smaller grain size, and reduced reduction of Ti4+ to Ti3+, associated with the applied external pressure and lower sintering temperature. Eventually, large power density (18.20 MW/cm3) is obtained in pulse overdamped discharge circuit. Meanwhile, the stored energy is also released in a short time (about 11.3 ns to release 90% of saturated energy density value). [ABSTRACT FROM AUTHOR]

The (1-x)(Ba 0.94 Li 0.02 La 0.04)(Mg 0.04 Ti 0.96)O 3 -xBi(Zn 1/2 Ti 1/2)O 3 ((1-x)BLLMT-xBZT, x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12) ceramic thick films were prepared by traditional solid-state sintering method combined with film scraping process. Li+ and La3+ ions doping at A-site, and Mg2+ and Zn2+ ions doping at B-site of the perovskite structure, and adding BZT component enhance charge compensation, enlarge polarization difference, increase breakdown strength, and enhance relaxation degree, leading to the improved pulse charging and discharging energy storage performance of the BaTiO 3 -based ceramic films. The 0.92BLLMT-0.08BZT ceramic film has high discharge energy density of 4.61 J/cm3, high pulse power density P D = 224.14 MW/cm3, high current density C D = 896.58 A/cm2, high discharge speed of 234 ns, and high pulse discharge density W d = 4.61 J/cm3 under 500 kV/cm combined with high breakdown strength of 500 kV/cm, relating to charge compensation, multiple ferroelectric phases coexistence, and formation of polar nanoregions. The strategy by equivalent and heterovalent ions doping at A-site and B-site of the perovskite structure and introducing Bi-based component combined with film scraping process strengthens charge compensation, enhances relaxation characteristic, and reduces grain size, providing an efficient route to develop prospect BT-based dielectric ceramic capacitors for potential application in high-power pulse energy storage such as 0.92BLLMT-0.08BZT. • Ultrahigh pulse energy storage property was obtained in 0.92BLLMT-0.08BZT ceramic film by combining defect engineering and film scraping. • Multi-ferroelectric phases coexist in (1-x)BLLMT-xBZT, which changes from tetragonal to pseudo cubic and rhombohedral with increasing BZT. • 0.92BLLMT-0.08BZT has best performance with W d (4.61 J/cm3), C D (896.58 A/cm2). • P D (224.14 MW/cm3), t 0.9 (234 ns) at 500 kV/cm, and excellent temperature stability. • 0.92BLLMT-0.08BZT has good temperature stability of 18.18 % within 30–170 ℃ at 150 kV/cm. [ABSTRACT FROM AUTHOR]

In this work, [(Bi 1- x La x) 0.5 Na 0.5 ] 0.94 Ba 0.06 (Ti 1-5y/4 Nb y)O 3 ceramics have been developed by the dual-substitution of La3+ for Bi3+ and Nb5+ for Ti4+ and prepared by an ordinary sintering technique. All ceramics can be well-sintered at 1200 °C. The addition of La3+ and Nb5+ reduces the grain size and improve the dielectric breakdown strength of the ceramics; moreover, after the introduction of La3+ and Nb5+, the remanent polarization of the ceramics is significantly reduced, while the maximum polarization remains the same large value as that of the ceramic without the doping of La3+ and Nb5+. As a result, high energy storage density and discharge efficiency are achieved at x /y = 0.07/0.02, giving the large storage density of 1.83 J/cm3 and high discharging efficiency of 70%. The present work presents a feasible strategy to develop energy storage materials based on perovskite ferroelectrics by the partial substitutions in the A and B sites. [ABSTRACT FROM AUTHOR]