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Recently, NaNbO3-based ceramics with excellent energy storage performances (ESPs) and fast charge-discharge characteristics have attracted great attention. In this case, BaTiO3 modified 0.85NaNbO3-0.15Bi(Zn2/3Nb1/3)O3 (0.85NN-0.15BZN-yBT) ceramics were designed and successfully fabricated using solid state synthesis. The discharge storage density of the ceramics increases from 1.22 J/cm3 at y = 0–1.84 J/cm3 at y = 8%, which is 1.5 times higher than pure 0.85NN-0.15BZN ceramics. This ceramic reveals excellent temperature stability up to 150 °C, good discharge cycling after 105 cycles and high discharge speed of 2.0 μs, broadening the scope of NaNbO3-based ceramics for energy storage applications.

Improving energy storage density and efficiency is the ultimate goal of dielectric materials used in ceramic capacitors. Among different dielectric materials, dielectrics in thin film state own superior energy performances due to less defects compared with ceramic. Herein, we report an optimized lead-free Zr-modified BiMg0.5Zr0.04Tix-0.04O3 composition with enhanced energy storage behavior via microstructural engineering. Rapid annealing can result in poorly crystallization in the film matrix confirmed by grazing incident X-ray diffraction GIXRD. The excess Ti source can effectively increase polarization and dielectric breakdown till to 97.0 μC/cm2 and 3403 kV/cm at x = 0.775, respectively. The optimized energy properties can be achieved at x = 0.775 with a high recoverable energy storage density Wreco of 87.8 J/cm3 and an efficiency η of 50%, indicative of excellent stability of storing electricity for the applications of pulse power electronics.

A core-shell structural nanoparticles preparative technique was applied to produce BaTiO3@NiO ceramics with excellent energy storage performance. Shell layers of NiO were coated onto BaTiO3 nanoparticles by sol-precipitation method. The structures, dielectric and energy storage properties of the BaTiO3@NiO ceramics were systematically investigated. Results show that, high-densification microstructures with fine-crystalline and uniform distribution are observed in all the ceramics, and excellent energy storage density of 2.72 J cm−3 with low remnant polarization is achieved at 230 kV cm-1 in BaTiO3@1 %NiO ceramics, which also possesses fast discharge features (τ0.9

Energy storage dielectric ceramics play a more and more important role in power or electronics systems as a pulse power material, and the development of new technologies has put forward higher requirements for energy storage properties. Here, the sol-gel method was used to synthetize the 0.9BaTiO3-0.1Bi(Mg1/2Zr1/2)O3 (0.9BT–0.1BMZ) precursor powder and 0.9BT-0.1BMZ ceramics with pseudocubic phase was obtained. The 0.9BT-0.1BMZ dielectric ceramics possessed a strong relaxation behavior with 1.64 relaxation degree (g) and 0.15 eV relaxation activation energy (Ea) fitted by modified Curie–Weiss law and Vogel-Fulcher formulas, respectively. The most important was that by controlling the grain size to be reduced, the discharge energy storage density had been improved to 2.0 J/cm3 with high breakdown strength (325 kV/cm). In addition, the comprehensive analysis of electric field distributions, breakdown paths, and impedance spectra was illustrated the enhanced grain boundary effect can improve the energy storage performance obviously.

[(0.12BiAlO3-0.88BaTiO3)+0.5 wt%Nb2O5]+x wt.% B–Al–Si glass ceramics (x = 0, 1, 2, and 4) were prepared by solid-state method. The effects of B–Al–Si glass additive on microstructural and electrical properties were investigated. After the adding of B–Al–Si glass, quartz appeared as a new impurity phase and the average grain size of the samples decreased (from 540 nm to 330 nm). All the samples satisfy the EIA X8R specification, meanwhile, the breakdown strength (BDS) increased (from 17 kV/mm to 29 kV/mm) with the rising glass content. The ratios of relaxation time of grain boundary to grain (τgb/τg) of the ceramics at 460 °C were calculated according to the complex impedance data. It is found that decreased value of τgb/τg suggests a weakened interfacial polarization effect after B–Al–Si glass addition, which is beneficial to the BDS performance of ceramics.

The solid-state sintering route was employed for the production of (1-x)Bi2(Li0.5Ta1.5)O7-xTiO2 (x = 0, 0.02, 0.04, 0.06, 0.08) ceramics. The phase, microstructure and microwave dielectric properties of each ceramic composition were determined via X-ray diffraction, scanning electron microscopy and Haki Colmon resonator technique, respectively. The dielectric constant, tan δ and AC conductivity were also determined for the composition of x = 0.04. The TiO2 addition developed new phases of Bi3Ti4O12 and Bi3TaTiO9 for x = 0.04 along with Bi2(Li0.5Ta1.5)O7 phase which disappeared for x = 0.08. The τf of Bi2(Li0.5Ta1.5)O7 was tuned through zero by TiO2 addition and good microwave dielectric properties er~67.2, Qufo13,767 GHz and τf ~ −1.45 ppm/°C can be obtained for the composition of x = 0.04 sintered at 1050 °C for 2 h. This ceramic composition is a suitable candidate for 5G cellular base station resonator application.

The epoxy resin (E-51) was used as polymer matrix, conductive carbon black (CB) as conductive filler, and PZT was used to prepare a composite by curing. The effects of PZT and CB content on the properties of PZT/ CB/ EP piezoelectric composite were studied. When the PZT content reaches 40 wt%, the optimized vibration attenuation properties of PZT/CB/EP materials could be achieved with a loss factor of 0.9 from room temperature to 60 °C. With the increase of PZT content, the bending strength of PZT/CB/EP piezoelectric composite vibration reduction material firstly increased from 45 MPa to 65 MPa and then decreased to 38 MPa. At room temperature, the dielectric constant increased from 7 to 50, and the dielectric loss increased from 0.1 to 0.5.

Effects of different sintering atmospheres (O2 and air) on the energy storage properties and dielectric characteristics were systematically investigated for 2MgO–2Al2O3–5SiO2 (MAS)-coated Er0.02Sr0.97TiO3 (EST) ceramics. The core–shell structure was formed by the sol-precipitation method. The ceramic sintered in O2 features fine grain, excellent frequency stability, low leakage current, high dielectric breakdown strength (BDS), and high energy storage density (Wreco). Compared with air-sintered ceramics, the dielectric DC breakdown strength of ceramic sintered in oxygen atmosphere has been enhanced significantly from 375 to 590 kV/cm. Besides, the maximum Wreco of 2.01 J/cm3 and efficiency of 86.2% were obtained at 460 kV/cm, which demonstrated that the core–shell structure and atmosphere sintering provide an instructive strategy for the design of high energy storage materials.

A comparison between poly(vinyl alcohol) (PVA)-formed (TYPE-I), Ba(OH)2/TiO2 [Ba/Ti] suspension-formed (TYPE-II), and cold isostatic pressed (CIP) pellets (TYPE-II+CIP) of 0.9BaTi1–xCaxO3-x–0.1BiAl...

Nb-containing antiferroelectric materials have recently attracted great research interest as energy storage materials for pulsed power capacitors due to their extraordinary energy storage performances. In this case, the optimization of the energy storage performance is obtained by a compositional modulation of NaNbO3-Bi(Zn2/3Nb1/3)O3 bulk ceramics. An optimal energy performance can be obtained with a composition of 0.85NaNbO3-0.15Bi(Zn2/3Nb1/3)O3, which is accompanied by a stable charge energy density in temperatures up to 150 °C owing to its relaxor characteristics and excellent cycling stability after 105 cycles. This work further broadens the scope of NaNbO3-based ceramic applications in the area of pulsed power sources.

This letter replies to the comments by Tkach et al. on our previous publication about the issues of ZnO volatilization, Ti3+ content and lattice constant etc. In this reply, we present a detailed discussion and rebuttal on the issues concerned in the comments.

Relaxor-ferroelectric ceramics capacitors have been in the front lines of investigations aimed at optimizing energy density due to their high Pmax, suppressed Pr, and high BDS levels, attributed to their highly dynamic polar nano-regions. A set of (1 − x)SrTiO3–x[0.88BaTiO3–0.12Bi(Li0.5Ta0.5)O3] ceramics (x = 0, 20, 40, 60 and 80 mol%), abbreviated as (1 − x)ST–x(BT–BLT), was designed and fabricated via a solid-state reaction route. A striking energy-storage density of 2.24 J cm−3, coupled with a high efficiency of η = 81% at 300 kV cm−1, was measured for these (1 − x)ST–x(BT–BLT) ceramics. The incorporation of BT–BLT ceramics was found to dramatically transform the paraelectric state of strontium titanate into the relaxor-ferroelectric state, by introducing broad relaxor behavior. The energy storage properties of the ceramic with x = 60 mol% showed outstanding stability in frequency (10–100 Hz) and temperature (20–120 °C), with minimal variation of (±≤0.5%), over the course of 105 cycles. Moreover, under various electric fields, rapid charge and discharge (≤1.5 μs) was also observed for this x = 60 mol% ceramic. Most significantly, the outcomes of this study are expected to provide a standard for other emerging lead-free dielectric ceramics displaying very good energy-storage properties and excellent electric field endurance, which are of pragmatic importance for cutting-edge pulsed power technology.

Defect engineering is applied to induce controllable changes in structures and dielectric behaviors in oxides. SrTiO3 ceramics modified by complex ions (Nb, Zn)x+ (x = 2, 3, 4 and 5) with variable valence states are prepared by standard solid state method. Phase structures, microstructures, defect structures and dielectric properties of the (Nb, Zn) co-doped SrTiO3 ceramics have been systematically investigated. In acceptor co-doping, M2 ceramics (x = 2) exhibits extremely low dielectric loss (≤0.001). M3 ceramics (x = 3) shows low conductivity and excellent thermal stability. In equivalent co-doping, M4 ceramics (x = 4) possesses giant permittivity and low dielectric loss. In donor co-doping, M5 ceramics (x = 5) presents improved permittivity while deteriorated dielectric loss. Further investigations reveal that oxygen vacancy is beneficial to the localization of charge carriers and then the low tangent loss, while excess electrons not only contribute to the improved permittivity but also result in high dielectric loss. Appropriate concentrations of oxygen vacancy and electron are significantly important for the formation of multiple defect dipoles or defect clusters, and therefore the greatly modified dielectric properties. The findings may facilitate the ability to engineer the advanced electronic materials.

Dielectric capacitors with high energy storage properties are key enablers for potential applications. We report SrTi0.985(Zn1/3Nb2/3)0.015O3–x wt%ZnNb2O6 ceramics with high breakdown strength and energy storage performance by synergy manipulation. The structures, energy storage and dielectric properties of the ceramics are systematically investigated. Introduction of ZnNb2O6 mediates the contradiction between permittivity and breakdown strength. As a result, a high breakdown strength of 422 kV cm−1 and an excellent energy storage density of 2.35 J cm−3 are achieved in x = 4.5 ceramics, which also exhibit fast discharge features (τ0.9 < 1.5 μs), good thermal stability (25–150 °C) and outstanding cyclic characteristics (up to 5 × 105 times). Further results indicate that ZnNb2O6 additives partly dissolve into perovskite lattices to promote the formation of superlattice structures, improving the local polarization, and partly disperse around grain boundary regions to inhibit grain growth and relieve the direct damage from a strong electric field to grains, increasing the breakdown strength. This strategy should be generalizable for designing high performance dielectrics and other novel composite materials that benefit from synergistic effect manipulation.

Effects of sintering and annealing atmosphere on the defect structures and the dielectric behaviors of (Nb + Zn) co-doped SrTiO3 ceramics are systematically investigated. Giant permittivity (~50,100), low dielectric loss (~0.04) and wide temperature (25–330 °C)/frequency (20–105 Hz) stabilities are achieved in the N2 sintering ceramics. Further investigations indicate massive defects and defect clusters are involved, contributing to the giant permittivity. The associated defects not only restrain the ionization of oxygen vacancy, but also localize the motions of oxygen vacancy and electron, resulting in the low dielectric loss and the suppressed relaxation peaks.

0.5Bi 0·5 Na 0·5 TiO 3 -0.5SrTiO 3 -x wt% MgO (x = 0, 0.5, 1.0, 1.5, 2.0, 3.0) ceramics were fabricated via solid-state method. The effect of MgO doped on energy storage properties, dielectric performance, phase structure and microstructures of 0.5Bi 0·5 Na 0·5 TiO 3 -0.5SrTiO 3 (BNST) ceramics were studied systemically. The Mg 2+ substituted Ti 4+ site in BNST, which was confirmed by X-ray diffraction (XRD) result. The scanning electron microscope (SEM) images show that all the ceramic samples exhibit uniform and compact morphologies. The temperature dependent permittivity exhibits frequency dispersion, indicating that the ceramic samples are typical relaxor ferroelectrics. It was found that MgO doped BNST can significant improve the breakdown strength (E b ) of samples from 109 kV/cm to 227 kV/cm, which results in a great enhancement on energy storage density. The sample of x = 3.0 has the largest energy storage density (2.17 J/cm 3 ), which is twice as much as the BNST. Consequently, we consider that MgO-doped BNST ceramics are able to be a promising candidate in the field of pulsed-power devices.

In this work, nominal composition (1-x)BaTiO3-xBi(Zn0.5Y0.5)O2.75 [abbreviated as (1-x)BT-xBZY, (x = 0.05, 0.1, 0.15, 0.2, 0.25)] ceramics were prepared by solid-state reaction method, and sintered in reducing atmosphere. Effect of introducing BZY on the structure, dielectric and insulating properties of BT was investigated. XRD results demonstrated that the unit cell volume of (1-x)BT-xBZY ceramics expanded with the addition of BZY, accompanied with the transformation from tetragonal to pseudo-cubic phase when x ≥ 0.05. Electrical properties measurement showed that the dielectric-temperature stability and insulating properties of (1-x)BT-xBZY ceramics were effectively improved by BZY addition, where the optimum performances were achieved at x = 0.15, with the dielectric constant of 1362 and dielectric loss of 1.4%, and resistivity of 5.5 × 1012 Ω cm at room temperature, meeting the standard of X8R specification for MLCC application. The feasible mechanism of improved anti-reduction properties for (1-x)BT-xBZY ceramics was investigated by employing X-ray photoelectron spectra (XPS) and thermally stimulated depolarization current (TSDC) testing techniques, where the formation of defect dipoles [2YTiˈ- V O .. ] and the deoxidation of Bi ion were revealed and considered to be responsible for the anti-reduction behavior.

Lead-free (1-x)BaTiO3-xBi(Mg1/2Zr1/2)O3 ((1-x)BT-xBMZ) ceramics with perovskite structure were synthesized by solid-state reaction methods. (1-x)BT-xBMZ solid solution transforms from tetragonal (x≤0.04) to pseudocubic (x≥0.08) and exhibits a dispersive dielectric behavior with respect to frequency, showing typical relaxor characteristics with BMZ increasing. The optimal energy storage density of 1.25 J cm−3 and energy efficiency of >95% are obtained at x = 0.15, with maximum dielectric breakdown strength of 185 kV cm-1 at 200 μm thickness., The energy storage density and energy efficiency of 0.85BT-0.15BMZ ceramics maintain at about 0.8 J cm−3 and 89% at 150 kV cm-1 over temperature range of 25 °C∼150 °C, exhibiting good thermal stability. The pulse discharge capability of 0.85BT-0.15BMZ ceramics were measured under different electric fields, showing a short charge-discharge time of 1.3 μs. Therefore (1-x)BT-xBMZ solid solution with high energy density and efficiency, good temperature stability and fast discharge speed, is promising candidate for high power applications.

In this work, the phase structure of BaTiO3 nanopowders produced by the alkoxide-hydroxide and the hydrothermal method, respectively, was systemically investigated. BaTiO3 nanopowders with cubic phase produced by the alkoxide-hydroxide method could transform to tetragonal phase when heated to about 1100 °C. Cubic to tetragonal phase transformation behavior of BaTiO3 nanopowders coated with 0.3BZT-0.7BT or 0.03Nb2O5-0.01Co2O3 was studied. The internal stress within core-shell structure was proposed to explain the BaTiO3 phase transformation behaviors. The mismatch of thermal expansion coefficient between core and shell plays a crucial role in cubic to tetragonal phase transformation of BaTiO3. By tuning the composition of shell and the ratio of the shell to the core, the cubic BaTiO3 core can transform to tetragonal phase successfully after sintering at 1100 °C in BaTiO3 based ceramics with core-shell structure and it is mainly resulted by the reduced internal stress between the shell and core.

(1−x)[0.94Bi0.5Na0.5TiO3 – 0.06BaTiO3]−xLa0.33NbO3 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) (BNBT-LN) bulk lead-free relaxor ferroelectric ceramics were synthesized via solid-state sintering method. Phase, microstructure and energy storage properties were determined. The X-ray diffraction (XRD) revealed a single perovskite phase for compositions of x ≤ 0.02, while the second phase of Bi2Ti2O7 along with the parent phase for x ≥ 0.04. Dense microstructure with a decrease in grain size has been achieved via LN doping. The addition of LN decreased the remnant polarization (Pr), and coercive field (Ec), while increased the difference between the maximum polarization (Pmax) and remnant polarization (Pr). The high energy-storage density of 2.96 J/cm 3 and high recoverable energy density of 1.66 J/cm3 at a breakdown electric field of 214 kV/cm were achieved for the composition of x = 0.02 with good temperature stability satisfying the condition of Δer /e r200 °C ≤ ± 15% in a working temperature range of 70 °C to 400 °C. Similarly, a less discharge time of

Solid-state sintering method was used for the synthesis of Mg1−xCoxSiO3 (x = 0–0.25) ceramics. Phase, microstructure and microwave dielectric properties of the ceramics were investigated. With increase in Co2+ content, the increase was observed in the lattice parameters. The Qufo value of MgSiO3 was enhanced from 103,453 to 145,846 GHz with increasing the value of x content from 0 to 0.15. The Co2+ substitution also led to an obvious decrease in the sintering temperature by ~ 100 °C. Clino-enstatite phase formed for the composition with x = 0 while Proto-enstatite formed as the major along with minor clino-enstatite phase for the compositions with x > 0. Good dielectric properties at microwave frequencies i.e. er ~ 8.11, Qufo ~ 145,846 GHz and τf ~ − 12 ppm/°C were obtained for the composition with x = 0.15 sintered at 1350 °C for 9 h. This is suggested to be a very favorable dielectric material for millimeterwave applications.

High permittivity materials continue to arouse considerable interest due to their applications in the field of high performance capacitors. However it is still a challenge to make material both with stable high permittivity and low dielectric loss. Here, the Sr1-3x/2CexTiO3 (SCT) ceramics are synthesized via solid-state reaction process and sintering in air. The sample (x = 0.01) exhibits a high permittivity of ∼7000 and low dielectric loss of ∼0.007 at room temperature and 1 kHz. Moreover, the dielectric properties are stable over a very broad temperature and frequency range. Further investigations reveal that the high permittivity is related to the defect chemistry caused by the trace Ce ions doping. The Ti3+ ions substitute the Ti4+ ions lead to the Ti-O octahedral off-center, which make a certain contribution to improve the permittivity. The low dielectric loss is owing to the fact that the defects are more likely to be in the form of defect clusters in the Ce doped SrTiO3 monophase solid solutions. The appropriate defect chemistry design suppresses the dielectric loss relaxation peak of Sr1-xCexTiO3 (x = 0.01) caused by the motion of oxygen vacancies.

The fine-grained silica-coated Ba0.3Sr0.7TiO3 (BST) ceramics were prepared by conventional solid-phase sintering method, the size of matrix materials which were produced by oxalate co-prepared method is about 100 nm. With the increase of the content silica, the grain size of ceramic dropped from 2 µm (pure BST) to 300 nm (Ba0.3Sr0.7TiO3-3 wt% SiO2) and the polarization of ceramic decreased under the same applied electric field, but the energy storage efficiency increased significantly. At the same time, the dielectric breakdown strength (BDS) increased significantly with the decrease of grain size and the addition of SiO2. For Ba0.3Sr0.7TiO3-3 wt% SiO2 ceramic, due to the small grain size, the BDS increased from 130 kV/cm to 380 kV/cm, its discharge energy storage density is 1.52 J/cm3 while the energy storage efficiency reaches 82.2%. The discharge energy density of the Ba0.3Sr0.7TiO3-3 wt% SiO2 ceramic increased to 3.3 times than that of pure Ba0.3Sr0.7TiO3 ceramic.

Phase, microstructure, and microwave dielectric properties of (Mg0.95Co0.05)(Ti1−xSnx)O3 (0.05 ≤ x ≤ 0.20) ceramics prepared via the conventional solid-state route were investigated. X-ray diffraction analysis showed the existence of a single phase for the compositions with Sn4+ ≤ 0.15; however, a further increase in Sn4+ caused the formation of a secondary SnO2 phase in the ceramics. The maximum observed densities of the single phase ceramics were higher than 95% of the theoretical density. An increase in the lattice parameters of the ceramics were observed with an increasing Sn4+ content. Dense microstructures were observed for the single phase ceramics at a sintering temperature of 1400°C, whereas a porous microstructure was observed for the ceramics with secondary phase. The unloaded quality factor (Qufo) of the ceramics was found to increase initially with an enhancing Sn4+ content from 0.05 up to 0.15; however, a sudden downfall was detected with a further enhancement in Sn4+. The dielectric constant and temperature coefficient of resonant frequency of the ceramics were observed to decline monotonically with enhancing Sn4+ content.

The effects of sintering temperature on microstructure and dielectric properties of Ce doped SrTiO3 were investigated. The dielectric properties are strongly depend on sintering temperature, the sample sintered at 1520 °C exhibits a colossal permittivity about 7000 at 1 kHz while relative permittivity of the sample sintered at 1380 °C is 770. Further investigations demonstrate that all the samples belong to P m 3 ¯ m space group and without secondary phase. The lattice parameter decrease with the increase of sintering temperature while the mean grain size of SCT (Sr0.985Ce0.01TiO3) ceramics are increased. Higher sintering temperature helps to improve the dielectric properties which can be attribute to defect clusters (e.g. oxygen vacancies, Ti3+/Ti4+ etc.), however the defects are more likely to become carriers in high electric field which can increase the conductivity and leakage current. With the increase of sintering temperature, the conductivity activation energies, breakdown strength and energy storage density of the samples are decreased.

Sr0.99Ce0.01Ti1-xO3 (SCT, x = 0, ± 0.0025, ± 0.0050, 0.0075) ceramics were prepared by solid state reaction methods and sintered in air atmosphere at different temperatures, with a soaking time of 2 h. The dielectric properties of all samples presented excellent temperature independence over a broad temperature range from 25 to 330 ℃ and frequency independence between 10 kHz and 1 MHz. Sr0.99Ce0.01Ti0.9925O3 (SCT0.9925) ceramics sintered in air atmosphere exhibited a high permittivity (~5400) and a low dielectric loss (~0.01) measured at room temperature and 1 kHz. XPS and complex impedance spectroscopy analysis confirmed that the high permittivity and low dielectric loss were attributed to the fully ionized oxygen vacancies and giant defect-dipoles in Ti-deficient samples. However, a higher dielectric loss of Ti-rich samples is owing to the destruction of giant defect dipoles, in which highly localized electrons were transformed into hopping electrons.

We explored the phase structure, microstructure, dielectric and energy storage properties of MgO-modified strontium barium niobate Sr0.7Ba0.3Nb2O6-xwt%MgO (SBNMx; x = 0–5) ceramics fabricated via conventional solid-state sintering precess. X-ray diffraction analysis indicates Mg2+ incorporates into lattice at x = 0.5 and secondary phases come into formation for samples at x ≥ 1, which results in the decrease of dielectric constant. There is also significant reduction of dielectric loss up to 0.002. Compared with pure SBN ceramics, the grain size of SBNMx ceramics becomes denser and more uniform, moreover, the dielectric breakdown strength shows increasing trend from 137 kV/cm to 226 kV/cm, which is in favor of the energy storage. SBNM0.5 ceramics presents the optimal energy storage performance: energy storage density of 0.93 J/cm3 and energy storage efficiency of 89.4% at 157 kV/cm, indicating that SBNM ceramics are prospective candidates for high voltage capacitor applications.

BaTi1-xCaxO3-x [BTC100x] ceramics were synthesized via solid-state reaction method. Effect of Ca substitution on the structure, electrical and dielectric properties of BTC100x ceramics was systematically investigated. Calcined BTC100x powders were in tetragonal phase when x ≤ 0.01, whereas transformed to cubic at x > 0.01. Additionally, the diffraction peak (200) shifted to lower angles with increasing x, indicating increased unit cell volume. Meanwhile, Ba0.97Ca0.03TiO3 [BC3T] ceramic was prepared and studied, to compare with BaTi0.97Ca0.03O2.97 (BTC3). It was found that pure BaTiO3 [BT] and BC3T ceramics had the similar structural and dielectric properties, whereas BTC3 ceramic showed much difference，XRD patterns, Raman spectrum, impedance spectra and dielectric-temperature spectra provided strong evidence of Ca2+ substitution at Ti site in BT lattice. Finally, BTC100x ceramics were produced and dielectric properties were investigated. With increasing x, the Curie temperature decreased from 128 °C (BT) to 42 °C (BTC5).

Different oxygen treatment methods, including O2 and N2 annealing, were conducted on Ca0.6Sr0.4TiO3 (CST) ceramics with varying Mn content (0 mol%, 0.5 mol% and 2.0 mol%). Structure characterization, including XRD and SEM, indicated the minimal effect of annealing on the microstructure. Grain boundaries were found to be sensitive to oxygen treatments, and annealing in O2 resulted in increased grain boundary resistance, while in N2 led to the opposite result. The insulating properties of bulk ceramics were found to be dominated by grain boundaries. Both the concentration and mobility of oxygen vacancies were confirmed to affect the energy storage properties to some extent in this work.

The fundamental characteristics of varied initial core-sizes of BaTiO3(BT) and its influential role on the morphology and dielectric properties of BaTiO3@0.6BaTiO3-0.4BiAlO3(BT@0.6BT-0.4BA) ceramic samples were studied. Alkoxide sol-precipitation method was adopted as revised chemical route to synthesize the constituent “core” BT powders in a dispersed phase, whereas the distinctive initial nano-sized particles were affected by the pre-calcination temperatures (600-900 °C).The microstructure of the uncoated BT ceramics revealed an exaggerated grain growth with an optimized dielectric constant (emax >9 000) whilst the coated ceramics behaved otherwise (grain growth inhibited) when sintered at an elevated temperature. Regardless of the previously studied solubility limit (about 0.1%) of BT-BA samples, BT@0.6BT-0.4BA maintained a maximum dielectric constant (emax) ranging from 1 592 to 1 708 and tan δ less than 2% under a unit mole ratio at room temperature. In view of all these analyses, the initial nanometer sizes of the as-prepared BT-core powders combined with the increase effect of cation substitutions of Bi3+ and Al3+ in the shell content, induced the diffuse transition phase of BT@0.6BT-0.4BA composition.

The phase, microstructure, and microwave dielectric properties of (1 − x)Mg(Ti0.95Sn0.05)O3–x(Ca0.8Sr0.2)TiO3 (0.01 ≤ x ≤ 0.07) ceramics were investigated. (Ca0.8Sr0.2)TiO3 was used as a τf compensator and was added to Mg(Ti0.95Sn0.05)O3 to obtain a temperature-stable material. The powder X-ray diffraction patterns suggest the presence of Mg(Ti0.95Sn0.05)O3 as the main crystalline phase and Ca0.8Sr0.2TiO3 and MgTi2O5 as the minor phases. With increasing (Ca0.8Sr0.2)TiO3 content, the dielectric constant er and the temperature coefficient of the resonant frequency τf of the ceramics increases, whereas the unloaded quality factor Qufo decreases. For 0.95[Mg(Ti0.95Sn0.05)O3]–0.05(Ca0.8Sr0.2)TiO3 ceramics sintered at 1375 °C, the dielectric constant er (21.1), the quality factor Qufo (117,000) at 9 GHz, and the temperature coefficient of the resonant frequency τf (−1.79 ppm/°C) were obtained.

Dielectrics for energy storage devices should commonly achieve the requirement of high permittivity, large breakdown strength, and large polarization when used in harsh working environments. A question is gradually raised about permittivity/polarization/breakdown strength in a dielectric for high voltage applications which one is more conducive to energy storage performances. Here, an attempt has been made to investigate the effect of high permittivity on the energy performances of dielectric materials in order to provide a viable option for high voltage devices. High values of dielectric permittivity (1300–7400) combined with low dielectric loss (

The microwave dielectric properties and microstructure of the new ceramic system (1 − x )Mg(Ti 0.95 Sn 0.05 )O 3 – x CaTiO 3 (0.02 ≤ x ≤ 0.08) prepared via a mixed-oxide route were investigated. To attain a temperature-stable material, CaTiO 3 was added to Mg(Ti 0.95 Sn 0.05 )O 3 as a temperature coefficient of resonant frequency ( τ f ) compensator. The compositions with 0.02 ≤ x ≤ 0.08 resulted in a mixture of two phases, Mg(Ti 0.95 Sn 0.05 )O 3 and CaTiO 3 , as confirmed by X-ray diffraction and energy-dispersive X-ray spectroscopic analyses. The values of the dielectric constant ( e r ) and the τ f of the ceramics were found to increase, and the unloaded quality factor ( Q u f o ) was found to decrease with increasing x values (i.e., increasing CaTiO 3 content). Excellent microwave dielectric properties of e r ≈ 21.5, Q u f o ≈ 112,500 GHz (at 9 GHz), and τ f ≈ 1.1 ppm/°C were attained for the 0.94{Mg(Ti 0.95 Sn 0.05 )O 3 }–0.06CaTiO 3 ceramic sintered at 1375 °C for 4 h.

xBa 0.7 Sr 0.3 TiO 3 -SrTiO 3 (BST-ST) multilayer ceramics with different BST layers (x=1, 3, 5) were designed and fabricated by lamination of Ba 0.7 Sr 0.3 TiO 3 (BST) and SrTiO 3 (ST) tapes. Dielectric and energy storage properties of the multilayer ceramics were investigated. BST-ST multilayer ceramics exhibited enhanced temperature- and frequency-stability of dielectric properties, accompanying high permittivity (~2000) and low dielectric loss ( 3 . These results indicate that BST-ST multilayer ceramics can be a favorable candidate for dielectric capacitor applications.

(1- x )Mg 0.90 Ni 0.1 SiO 3 - x TiO 2 ( x = 0, 0.01, 0.03, 0.05) ceramics were successfully formed by the conventional solid-state methods and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), and their microstructure and microwave dielectric properties systematically investigated. It was observed that when TiO 2 content increased from 0 to 5 wt%, the Q u f o of the sample decreased from 118,702 GHz to 101,307 GHz and increases the τ f value from −10 ppm/°C to +3.14 ppm/°C accompanied by a notable lowering in the sintering temperature (125 °C). A good combination of microwave dielectric properties (e r ∼ 8.29, Q u f o ∼ 101,307 GHz and τ f ∼ −2.98 ppm/°C) were achieved for Mg 0.90 Ni 0.1 SiO 3 containing 3 wt% of TiO 2 sintered at 1300 °C for 9 h which make this material of possible interest for millimeter wave applications.

In this paper, a core-shell structure, where the BaTiO 3 (BT) particles were coated with 0.25Bi(Zn 1/2 Ti 1/2 )O 3 -0.75BaTiO 3 [BT@x(0.25BZT-0.75BT)] by sol-gel method, was fabricated and confirmed by transmission electron microscopy (TEM). The impedance data of BT, 0.25BZT-0.75BT and BT@x(0.25BZT-0.75BT) (x=0.5–1.0) ceramics was collected and fitted by different equivalent circuits. The core and shell regions of BT@x(0.25BZT-0.75BT) (x=0.5–1.0) ceramics can be separated in complex impedance plots (fitted by a 4RC equivalent circuit), according to the activation energies of BT and 0.25BZT-0.75BT. The calculated activation energy of the core part in BT@x(0.25BZT-0.75BT) ceramics is relatively stable, being closer to the activation energy (0.86 eV) of BT, while the activation energy of the shell was found to increase from 0.28 eV to 0.53 eV with increasing the shell thickness. The average core/shell ratio (d gc /d gs ) for BT@0.8(0.25BZT-0.75BT) ceramics was found to be on the order of 7.26, calculated by a modified two-layer dielectric model. In addition, Lichtenecker formula was used to simulate the dielectric constant of BT@0.8(0.25BZT-0.75BT) ceramics at room temperature and the simulated results are in agreement with the measured values.

Effect of titanium deficiency on the structure and electrical properties of lead-free (Ba0.838Ca0.162)(Ti0.908-xZr0.092)O3 (0.46BZT-0.54BCTx, x = 0.000, 0.0004, 0.0008, 0.0012, 0.0016, 0.0020) compositions was investigated. The Ti-deficient compositions exhibited typically tetragonal-structured characteristics confirmed by XRD and Raman spectra regardless of trace amount of Ti deficiency. Ti-deficiency could result in double doping mechanism, namely soft characteristic for low Ti deficiency and hard characteristic for high Ti deficiency. Thermal stability of piezoelectricity could be effectively improved by Ti deficiency compared to pure 0.46BZT-0.54BCT, but inferior to Mn-doping composition. This defect engineering can be an effective and promising way to tailor the thermal stability of piezoelectric materials suitable for high temperature applications.

Thermal annealing treatments with different atmospheres (air, oxygen, and reducing atmospheres, respectively) were employed for the conventionally sintered (Ba0.4Sr0.6)TiO3 (BST) ceramics. The effect of thermal annealing on the energy storage properties of BST ceramics was investigated, where oxygen vacancies played an important role. The dielectric loss, bulk resistivity and dielectric breakdown strength (BDS) were found to be sensitive to the annealing process, leading to the different energy densities in the range of 0.30-0.80 J/cm3. Temperature-dependent dielectric measurement and thermally stimulated depolarization current analysis were conducted to understand the impacts of oxygen vacancies on the macroscopic properties, which were found to be closely associated with the annealing conditions.

We investigated the structure, dielectric properties and energy density performances of cubic perovskite-structured Mg-doped SrTiO3 ceramics that were prepared by the solid-state reaction method. SrTiO3 ceramic exhibited a relatively stable permittivity about 265–290 and enhanced dielectric breakdown strength (DBS) by Mg isovalent doping. Doping effects on the energy-storage properties in SrTiO3 ceramics was performed by complex impedance analysis and polarization–electric field hysteresis loops. The energy storage density was dependent on DBS while energy efficiency was closely related to the remnant polarization. The possible physical mechanisms, including grain, gain boundary and interfacial polarization effects, were discussed to explain the improvement of dielectric breakdown strength. The bulk Mg-doped SrTiO3 materials have shown interesting energy densities (1.86 J/cm3) with good energy storage efficiency (about 89.3%) indicating that they can be a promising candidate for high energy density capacitor applications.

A BaTiO3@FeO nanoceramic was successfully fabricated by chemical coating technique under sintering and achieved high energy storage capability. The FeO layer was coated onto BaTiO3 nanoparticles by sol-precipitation method. The structures, dielectric properties and energy storage capability of ceramics were systematically investigated. A high densification and nano-scale crystalline were observed after low temperatures sintering by this chemical coating technology and the grain size maintained about 70 nm. This chemical coating method is contributed to obtain dense nanocrystalline ceramics, benefiting to enhance the breakdown strength and energy storage density. The dielectric properties of BaTiO3@%FeO nanoceramics exhibit good temperature (−55 to 125 °C) and frequency(1 Hz–1 MHz) stability, indicating the fine dielectric quality of the ceramics. The BaTiO3@3%FeO nanoceramics present a high discharge energy storage density of 1.50 J cm−3 at 300 kV/cm-1 with a high energy storage efficiency about 88%. Moreover, the advanced energy storage properties with fast discharge features (τ0.9

Nanoceramics have a wide application in dielectric field due to their excellent dielectric properties.However, it is extremely difficult to fabricate densified BaTiO3with nanometer scale crystalline. In this study, nanoscaleBaTiO3 ceramics are successfully fabricated by deposition of a FeO layer onto BaTiO3 nanoparticle, and the structure and dielectric behavior of the BaTiO3@FeO nanoceramics are systematically investigated. The multilayer structure including 1) an inner tetragonal core, 2) a gradient lattice strain layer and 3) a surface insulating layer makes the dielectric constant peak tend to be rounded and broadened. Consequently, an excellent temperature/frequency stability met the X7R requirements and accompanied by the low dielectric loss are achieved in the BaTiO3@FeO nanoceramics.

The effects of Nb2O5 addition on the dielectric properties and phase formation of 0.8BaTiO3-0.2Bi(Znl/2Til/2)O3 (0.8BT-0.2BZT) ceramics were investigated. The desired perovskite phase was achieved with Nb2O5 doping levels being in the range of 0.5 wt.%–3.0 wt.%. The 0.8BT-0.2BZT ceramics doped with 1.5 wt.% Nb2O5 was found to possess a moderate dielectric constant (e = 1170) and low dielectric loss (tanδ = 1%) at room temperature and 1 kHz frequency, showing a flat dielectric behavior over the temperature range of −55 °C–200 °C. Based on this composition, the X9R-MLCC (multilayer ceramic capacitor) with Ag0.7-Pd0.3 electrode was sintered at 1060 °C. The optimized capacitance of the MLCC is 26.5 nF, with dielectric loss tanδ of 0.9% and electrical resistance of 4.50 × 1011 Ω at room temperature, leading to a high time constant of 11,900 s, decreasing to 175 s at 200 °C, being one order higher than those of commercial X7R MLCC. In addition, the equivalent series resistance (ESR) was found to be on the order of 0.2 mΩ at 2 MHz, much lower than that of the DC Bus Capacitor Bank for the automotive inverters (where the desired characteristic is

Mg 1−x Zn x SiO 3 (x=0–0.3) ceramics were successfully synthesized by conventional solid-state methods and characterized by scanning electron microscopy, dispersive X-ray spectroscopy, and X-ray diffraction. The microstructures and microwave dielectric properties of Mg 1−x Zn x SiO 3 ceramics were systematically investigated. The lattice parameters of the samples with different Zn 2+ contents were analyzed. When the Zn 2+ content was increased from 0 to 0.15, the Q u f o of the sample increased from 103,453 GHz to a maximum 138,481 GHz. This also resulted in a significant lowering in the sintering temperature (90 °C). Monoclinic structured Mg 0.85 Zn 0.15 SiO 3 was detected without any secondary phase. In this study, a new combination of microwave dielectric properties (e r ∼8.05, Q u f o ∼138,481 GHz, τ f ∼−14 ppm/°C) was achieved for Mg 0.85 Zn 0.15 SiO 3 sample sintered at 1360 °C for 9 h. The prepared material with remarkable useful dielectric properties can be used for millimeter-wave applications.

0.93Bi0.5Na0.5TiO3-0.07BaTiO3 (BNTBT) and KNbO3 (KN) powders with average particle size of ∼50 nm and ∼300 nm were synthesized by sol-gel method and hydrothermal method, respectively. Then, (1 − x)(BNTBT)-xKN (BNTBT-KN, x = 0, 0.01, 0.03, 0.05, 0.07) ceramic samples were prepared using these two powder precursors. The structure, dielectric and energy-storage properties of BNTBT-KN ceramics were comprehensively investigated. All the ceramic samples were in single perovskite structure, indicating that KN can completely dissolve into BNTBT within the studied composition range. BNTBT-KN ceramics exhibited a high dielectric constant at room temperature, being in the order of 1430–1550. Ferroelectric hysteresis loops at room temperature became more slim with the increase of KN content, which largely improved energy-storage density and efficiency. For the composition of x = 0.05, the maximum recoverable energy-storage density reached 1.72 J/cm3 under 16.8 kV/mm, which is superior to linear dielectrics and even some Pb-based systems. All these results demonstrate that 0.95BNTBT-0.05KN fabricated by wet-chemical method is a promising lead-free dielectric material for energy-storage capacitors.

Nb2O5 doped 0.8BaTiO3–0.2(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 (0.8BT–0.2NBMT) polycrystalline ceramics were prepared by solid state reaction method. 0.8BT–0.2NBMT samples were observed to possess two dielectric peaks, which were attributed to the formation of core–shell structure (Huang et al. in J Eur Ceram Soc 36:533–540, 2015). Longer sintering induced uniform distributions of the additives. The introduction of Nb2O5 into 0.8BT–0.2NBMT could obviously bring about the improvement of the dielectric temperature stability, the degradation of the dielectric loss at room temperature and the decrease of the sintering temperature. The 0.8BT–0.2NBMT ceramics doped with 2.0 at% Nb2O5 could satisfy the temperature range of the X9R (−55 to 200 °C, △C/C25°C = ±15% or less) characteristics, with a moderate dielectric constant of 1130, low dielectric loss of 0.7%, low sintering temperature of 1050 °C and insulation resistivity of 5 × 1012 Ω cm at room temperature, which might be promising for practical use in multilayer ceramic capacitors. The inhomogeneous distribution and the existence of the secondary phases were responsible for this excellent dielectric temperature characteristic. The complex impedance analysis was introduced to elaborate the conduction mechanism.

The Ba x Sr 0.97−x Sm 0.02 TiO 3 (x=0–0.4) ceramics in different sintering atmosphere were prepared by conventional solid-state reaction methods. The effect of different atmosphere on the dielectric properties of Ba x Sr 0.97−x Sm 0.02 TiO 3 ceramics was investigated. The giant permittivity was obtained for Ba x Sr 0.97−x Sm 0.02 TiO 3 ceramics sintered in nitrogen especially for x=0.2, which exhibited a weak temperature- and frequency- dependent giant permittivity (>10 4 ) as well as a low dielectric loss (mostly 4+ ·e - V o . . - e·Ti 4+ ] generated by the fully ionized oxygen vacancies and Ti 3+ ions, while the defect dipoles ( V Sr , , − V o . . ) and interfacial polarization caused the dielectric relaxation of the ceramics sintered in air or O 2 .