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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.

The effects of sintering atmospheres (air, O2, and N2) and defect chemistry role of Mn in the structure, electrical properties, and conduction mechanism of Ca0.6Sr0.4TiO3 (CST) ceramics were extensively investigated in this study. O2 atmosphere sintering resulted in a decrease in the concentration of oxygen vacancies, as revealed by the expanded unit cell and increased Ti ions' valence state. The reverse was the case for samples sintered in N2. Interestingly, sintering in both of O2 and N2 resulted in deteriorated bulk resistivity, due to the transition of the conduction mechanism (n-type electronic→ionic→p-type electronic conduction) with increasing oxygen partial pressure (PO2). This was verified by subjecting the samples to annealing treatment in different atmospheres and measuring their high-temperature equilibrium conductivities. Additionally, Mn-doped CST ceramics demonstrated higher resistivity than that of the pure CST ceramics, regardless of the sintering atmospheres, which could be attributed to the self-changing of Mn ions’ valence state in different PO2.

There is a general observation that the Curie temperature and piezoelectric property of the ferroelectric ceramics can be enhanced only at the expense of each other, i.e., higher piezoelectricity, lower Curie temperature, thus, limits their applications over broad temperature range. In this research, Sm-modified 0.15 Pb(Mg1/3Nb2/3)O3-(0.85-x)PbZrO3-xPbTiO3 ceramics have been studied, where excellent piezoelectric coefficients d33 = 720 pC/N, d33∗ = 950 pm/V and high Curie temperature TC = 293 °C were simultaneously achieved for x = 0.42 composition by designing the morphotropic phase boundary (MPB) with local structural heterogeneity. Of particular significance is that a high thermal stability was observed with piezoelectric variation below 20% with temperature up to 280 °C, demonstrating that the x = 0.42 composition is a good candidate for piezoelectric application over broad temperature range where high temperature stability is required. This work provides a good paradigm for designing high-performance piezoelectric ceramics with high thermal stability via a combination of MPB and local structural heterogeneity.

Dielectric ceramic capacitors, with the advantages of high power density, fast charge-discharge capability, excellent fatigue endurance, and good high temperature stability, have been acknowledged to be promising candidates for solid-state pulse power systems. This review investigates the energy storage performances of linear dielectric, relaxor ferroelectric, and antiferroelectric from the viewpoint of chemical modification, macro/microstructural design, and electrical property optimization. Research progress of ceramic bulks and films for Pb-based and/or Pb-free systems is summarized. Finally, we propose the perspectives on the development of energy storage ceramics for pulse power capacitors in the future.

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.

Sodium niobate (NN)-based lead-free ceramic DyxNa1–x(Nb0.9Ta0.1)O3 denoted as (DNNT) x = 0, 0.05, 0.1, 0.2, and 0.3 was synthesized via a conventional solid-state method to achieve bulk lead-free d...

[(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.

Recent experiments reported voltage-controlled transitions from low spin to high spin in molecular junctions of spin crossover molecules, which could bring higher performance for related electronic devices. As for the mechanism, the voltage-controlled spin transition was probably attributed to the one-electron reduction of spin crossover molecules, and the (p–d)π bonding between the ligand and metal was regarded as the key factor for the reduction-induced spin transition. In this work, spin crossover molecules FeII[H2B(Pz)2]2(L) are taken as examples to explore the effect of the ligand on the (p–d)π bonding and the reduction-induced spin transition, based on density functional theory. Interestingly, when the number of aromatic rings increases in the L ligand the (p–d)π bonding generally grows weaker and even ignorable, which shows that the ligand can have a significant impact on the reduction-induced spin transition. If reduction is not obtained, the low spin configuration is, however, little influenced by the increase of the aromatic rings. We also quantify the effect of the (p–d)π bonding on the spin transition using energy decomposition analysis. Our study provides an important guide for design of functional materials and molecular devices using spin crossover molecules.

The current work presents the designed series of compositions within pseudocubic regions based on (1–x)La0.03Na0.91NbO3–xBi(Li0.5Nb0.5)O3 ceramics abridged as (1–x)LNN–xBLN meant for energy storage...

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...

Hydrogen peroxide (H2O2, 30%) dipping treatment was conducted on Mn-doped Ca0.6Sr0.4TiO3 (CST) in this research, to modify the concentration of oxygen vacancies in dielectric ceramics. Structure characterization, including XRD, SEM, IR, and XPS, indicated minimal effect of H2O2 dipping on phase structure and grain size, while revealed a chemical reaction between H2O2 and the surface of CST. Electrical properties of the grain region remained unchanged after treatment, while the grain boundary region was sensitive to H2O2 dipping, due to faster diffusion rate of oxygen vacancies in grain boundary region. In addition to that, the bulk insulating properties was found to be dominated by grain boundaries.

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.

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.

Lead free dielectric ceramics of 0.65Bi0.51Na0.47Ti1-5x/4NbxO3- 0.35Ba(Ti0.7Zr0.3)O3 (BB35-100xNb, x = 0.00, 0.01, 0.02, 0.04 and 0.08) are fabricated by conventional solid-state sintering method for potential energy storage applications. Benefited from the coexistence of relaxor and antiferroelectric features, a high recoverable energy storage density of 3.2 J/cm3, together with high energy efficiency of 93%, is simultaneously achieved in bulk BB35-1Nb ceramic at the critical electric field of 280 kV/cm. The studied BB35-1Nb ceramic exhibits a wide temperature usage range of 20–160 °C with energy density variation below 3%, and excellent cycling reliability with both energy density and efficiency variations less than 4% over 106 cycles, together with its fast discharge time of ˜1.2 μs, making BB35-1Nb ceramic promising candidate for high-temperature, high power energy storage applications.

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.

High-performance piezoelectric materials are pivotal to many electromechanical applications including piezoelectric actuators, sensors, and transducers. However, the general approach to achieve high piezoelectric properties by establishing morphotropic phase boundary (MPB) has limitation due to the weak anisotropy of the Gibbs free energy profile at the MPB region. Here, aliovalent Sm3+-doped 0.4Pb(Mg1/3Nb2/3)O3-(0.6-x)PbZrO3-xPbTiO3 piezoelectric ceramics were fabricated by a solid-state method, where the optimized piezoelectric coefficient d33 = 910 pC/N, dielectric constant er = 4090, and Curie temperature TC = 184 °C were obtained at x = 0.352, being attributed to the synergistic contributions from the MPB and enhanced local structural heterogeneity. Rayleigh analysis was adopted to study the intrinsic and extrinsic contributions in Sm-doped PMN-PZ-PT ceramics, where the extrinsic contribution was found to be on the order of 25-67% at 4 kV/cm. Of particular significance is that a large signal d33* = 820 pm/V (at 20 kV/cm) with a minimal strain variation of 5% was achieved for a composition of x = 0.372 over the temperature range of 20-160 °C, being superior to those previously reported piezoelectric ceramic materials. This work offers a good paradigm to simultaneously achieve high piezoelectric properties with good temperature stability in ferroelectric ceramics, which have great potential for piezoelectric application at elevated temperatures.

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.

Dielectric ceramics with high energy storage density and energy efficiency play an important role in high power energy storage applications. In this work, lead free relaxor ferroelectric ceramics in (1-x)Bi0.51Na0.47TiO3- xBa(Zr0.3Ti0.7)O3 (BNT-BZT100x: x = 0.20, 0.30, 0.40 and 0.50) system are fabricated by conventional solid-state sintering method. The BNT-BZT100x ceramics are sintered dense with minimal pores, exhibiting pseudocubic symmetry and strong relaxor characteristic. A high energy storage density of 3.1 J/cm3 and high energy efficiency of 91% are simultaneously achieved in BNT-BZT40 ceramic with 0.1 mm in thickness, at the applied electric field of 280 kV/cm. The temperature stability of the energy density is studied over temperature range of 20–160 °C, showing minimal variation below 1.5%, together with the excellent cycling reliability (the variations of both energy density and efficiency are below 3% up to 106 cycles), making BNT-BZT40 ceramic promising candidate for high-temperature dielectric and energy storage applications. Keywords: Energy storage, Lead free ceramic, Relaxor characteristic

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.

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.

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.

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.

(K,Na)NbO3 based ceramics are considered to be one of the most promising lead-free ferroelectrics replacing Pb(Zr,Ti)O3. Despite extensive studies over the last two decades, the mechanism for the enhanced piezoelectricity in multi-elements doped (K,Na)NbO3 ceramics has not been fully understood. Here, we combine temperature-dependent synchrotron x-ray diffraction and property measurements, atomic-scale scanning transmission electron microscopy, and first-principle and phase-field calculations to establish the dopant–structure–property relationship for multi-elements doped (K,Na)NbO3 ceramics. Our results indicate that the dopants induced tetragonal phase and the accompanying high-density nanoscale heterostructures with low-angle polar vectors are responsible for the high dielectric and piezoelectric properties. This work explains the mechanism of the high piezoelectricity recently achieved in (K,Na)NbO3 ceramics and provides guidance for the design of high-performance ferroelectric ceramics, which is expected to benefit numerous functional materials. The mechanism for the enhanced piezoelectricity in (K,Na)NbO3 based ceramics has not been fully understood. Here, the authors find that the dopants induced tetragonal phase and the accompanying high-density nanoscale heterostructures are responsible for the high dielectric and piezoelectric properties.

(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

The impact of phase structure on piezoelectric performances of &lt, 001&gt, textured Na0.5Bi0.5TiO3 (NBT) based lead-free ceramics was studied, including 0.88NBT-0.08K0.5Bi0.5TiO3-0.04BaTiO3 (88NBT) with morphotropic phase boundary (MPB) composition and 0.90NBT-0.07K0.5Bi0.5TiO3-0.03BaTiO3 (90NBT) with rhombohedral phase. Both textured ceramics exhibit a high Lotgering factor, being on the order of f~96%. The piezoelectric&nbsp, coefficients of the textured 88NBT and 90NBT ceramics are increased by 20% and 60%, respectively, comparing to their randomly oriented ceramics. The piezoelectric enhancement of 90NBT textured ceramic is three times higher than 88NBT, revealing the phase structure plays a significant role in enhancing the piezoelectric performances of textured ceramics. Of particular significance is that the 90NBT textured ceramic exhibits almost hysteresis-free strain behavior. The enhanced piezoelectric property with minimal strain hysteresis is attributed to the &lt, poled rhombohedral engineered domain configuration.

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).

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.

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 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.