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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.

Ca0.6Sr0.4TiO3 (CST) ceramics with different amounts of Mn dopant (0~2.0 mol%) were prepared by solid state reaction method. The electric field and temperature stability of energy storage performance was found to be greatly enhanced with moderate doped level of 0.5 mol%. The dielectric loss-frequency spectra revealed the existence and evolution of defect dipoles at elevated temperature, which was confirmed directly by electron paramagnetic resonance (EPR) spectra. The response of defect dipoles was characterized by thermally stimulated depolarization current (TSDC), where the activation energy and the concentration evolution of defect dipoles were calculated, with the highest values observed for 0.5% doped samples. The dissociation of defect dipoles and the movement of free Vo.. were analyzed by high temperature impedance spectra analysis, with the activation energy of 1.04~1.60 eV, and 0.5% doped samples also demonstrated the highest Ea. The relationship between microscopic defect structure and macroscopic electrical behavior was established in this work. This article is protected by copyright. All rights reserved.

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.

Nanoceramics have a wide application in dielectric field due to their excellent dielectric properties. However, it is extremely difficult to fabricate densified BaTiO3 with nanometer scale crystalline. In this study, nanoscale BaTiO3 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.

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

Lead-free (0.94-x)Bi0.5Na0.5TiO3–0.06BaTiO3−xSrTiO3 (abbreviated as BNT-BT-xST, x = 0, 0.05, 0.10, 0.15, 0.20) thin films were grown onto the Pt/Ti/SiO2/Si substrate via a sol-gel/spin-coating method. Effect of Sr introduction on the microstructures, dielectric properties and energy-storage density of the thin films was researched. As a consequence, the addition of ST enhanced the maximum polarization and dielectric constant of the thin films. BNT-BT-0.05ST thin film existed high maximum recoverable energy-storage densigty (Ue) 22.5 J/cm3, dielectric constant 1120 and low dielectric loss about 0.04 at 1 kHz. Moreover, the thin films showed excellent dielectric temperature stability at the measured temperature range among 25–200 °C. These results indicated that BNT-BT-0.05ST thin film can be a promising candidate for lead-free energy storage capacitor.

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 .

Piezoelectric properties and thermal stability of tetragonal-structured (Ba 0.838 Ca 0.162 )(Ti 0.908−x Mn x Zr 0.092 )O 3 (0.46BZT–0.54BCTMn) compositions away from morphotropic phase boundary (MPB) were investigated. The results demonstrated that the addition of small amounts of Mn did not cause a remarkable change in crystal structure, but resulted in an evident evolution in piezoelectric properties and thermal stability. Mn could induce combinatory hard and soft piezoelectric characteristics due to aliovalent substitutions and improve thermal stability. The optimal electrical properties were obtained in the modified composition at x=0.006 with piezoelectric constant d 33 =410 pC/N, planar electromechanical coupling factor k p =0.40, mechanical quality factor Q m =150, remnant polarization P r =14.1 μC/cm 2 , coercive field E c =4.44 kV/cm and a high Curie temperature T c ~99 °C, respectively. It can be expected that the improved piezoelectric material can be a promising candidate for lead-free piezoelectric applications.

SiO 2 -added barium strontium titanate ceramics Ba 0.4 Sr 0.6 TiO 3 - x wt%SiO 2 ( x =0, 0.5, 1, 3, BSTS x ) were prepared via a traditional solid state reaction method. The effect of SiO 2 additive on the microstructure, dielectric response and energy storage properties was investigated. The results confirmed that with the increase of SiO 2 additive, diffuse phase transition arises and the dielectric constant decreases. An equivalent circuit model and Arrhenius law were used to calculate the activation energy of grain and grain boundary, which indicated that the dielectric relaxation at high temperature was caused by oxygen vacancy. While appropriate SiO 2 additive led to improve the breakdown strength, further increase of SiO 2 deteriorated the energy storage because of the low densification. Finally, optimized energy storage performance was obtained for BSTS0.5 ceramics: dielectric constant of 1002, dielectric loss of 0.45%, energy density of 0.86 J/cm 3 and energy storage efficiency of 79% at 134 kV/cm.

Electric conduction and dielectric relaxation behavior in (1—x)(Bi 0.5 Na 0.5 TiO 3 -BaTiO 3 )-xNaNbO 3 ((1—x)(BNT–BT)–xNN) ceramics were investigated. All compositions showed negative temperature coefficient of resistance (NTCR) behavior. The bulk conductivity followed the Arrhenius law with E a = 1.24–1.55 eV, which can be attributed to the electronic conduction. In the modulus (M′′-f) spectra, a peak and a shoulder were observed, corresponding to the bulk and polar nano regions (PNRs) response respectively. With the increase of either temperature or NN content, the shoulder gradually depressed and even disappeared. A correlation between the PNRs evolution and the relaxation behavior was constructed.

SrSnxTi(1−x)O3 (x=0, 0.01, 0.03, 0.05, 0.07) dielectric ceramics were fabricated by the solid state reaction method. Significant refinement of grain size and improved resistivity were observed with the addition of Sn, accounting for effectively enhanced dielectric breakdown strength, beneficial for the energy storage applications. Impedance analysis was employed to calculate the conductivities of grain and grain boundary and resistance ratios (Rgb/Rg) of grain boundary to grain. The grain boundary effect was believed to dominate the modified macroscopic performance, which was confirmed by the complex impedance analysis. The optimal properties were achieved for samples with x=0.05, exhibiting a charge energy density of 1.1 J/cm3 and an energy efficiency of 87%.

The ceramics were prepared using the solid-state reaction method and their phase, microstructure and microwave dielectric properties were investigated. A single-phase clinoenstatite system with monoclinic structure (space group P21/c) was confirmed through x-ray diffraction (XRD) analysis for the compositions with x ≤ 0.1. The compositions with x ≥ 0.15 contain SiO2 and (Mg1−x Ni x )2SiO4 phases only as confirmed from the XRD data of their sintered samples. The unit cell volume was decreased while the theoretical density was increased with increase in x from 0 to 0.1. A decrease in dielectric constant (e r) while an increase in unloaded quality factor multiplying the resonant frequency (Q u f o) and temperature coefficient of resonant frequency (τ f) was observed with increase in Ni content from 0 to x = 0.1. In the present study, e r ∼ 6.10, Q u f o ∼ 118,702 GHz and τ f ∼ −10 ppm/°C was achieved for the composition with x = 0.1 sintered at 1425°C for 9 h. The material is a good candidate for millimeter wave applications.

Recently, dielectric energy storage capacitors obtain extensive attention and become a research hotspot owing to the high power density and ultrafast charge/discharge speed, while their applications are limited because of low energy storage density. Here, 1% Mn doped SrTiO3 (ST) thin films with different microstructure were prepared by modulating annealing temperature to optimize the energy storage performance. The X-ray diffraction analysis shows that the ST thin films annealed below 600 °C are amorphous structure while the thin film annealed at 700 °C is polycrystalline. The dielectric properties of amorphous ST thin films show outstanding frequency stability, electric field stability and temperature stability. The electric breakdown strength and discharge energy storage density of the thin films improve first, and then reduce with the annealing temperature. The optimal energy storage performance is obtained in ST thin film annealed at 550 °C: an ultrahigh discharge energy storage density of 53.9 J/cm3 with high efficiency of 77.2% at 4.541 MV/cm. It reveals that amorphous ST thin film is promising as dielectric energy storage devices in pulse power fields.

Compositional design by multiphase coexistence is regarded as a guiding rule for material design to develop high-performance piezoelectric materials. An open question is whether a certain PZT composition outside of the morphotropic phase boundary (MPB) region can obtain high piezoelectric response like that close to MPB region. Here, a non-MPB composition, rhombohedral Pb(Zr0.54Ti0.46)O3 was selected as the parent material. The optimized electrical properties were obtained by Sm doping with a large piezoelectric coefficient d33 of 590 pC/N, a high planar electromechanical coupling factors kp of 57.1%, a large piezoelectric strain S of 0.31% (d33∗ = 632 pm/V), and a promising Curie temperature of 335 °C, compared to the commercial PZTs. The enhancement of piezoelectric response can be ascribed to the donor characteristics by Sm replacement, which contribute to polarization orientation of ferroelectric dipoles. This work broadens the domain of high-performance piezoelectrics by developing novel solid solutions beyond the MPB framework.

The ceramics (1−x)SrTiO3-x (0.93Bi0.5Na0.5TiO3-0.07Ba0.94Sm0.04Zr0.02Ti0.98O3) abbreviated as ((1−x) ST -x (BNT-BSmZT)) (x = 0, 0.1, 0.2, 0.3) were synthesized via solid-state sintering route. The phase structure, microstructure, electrical properties and energy storage performances of the outlined compositions were investigated using X-ray diffraction, electron microscopy, and dielectric measurement techniques. The X-ray diffraction results reveal structural phase transformation from a perfect cubic structure to a rhombohedral structure as the x value increased from 0 to 0.3. The submicron grain size of ∼0.71 μm was obtained for x = 0.1. The rest of the parameters such as breakdown strength (BDS), energy storage performance, charge-discharge efficiency (η), discharging time, dielectric loss and electrical conductivity were observed to be affected by the homogeneous, compact microstructure and grain size. Herein we report an innovative ST-based lead free ceramics capacitor with the highest breakdown strength (BDS) of 420 kV/cm, an impressive recoverable energy density (Wrec) of 1.93 J/cm3, simultaneously with high efficiency (η) of 80.0%, moreover, low dielectric loss, low electrical conductivity ∼4.7 × 10−8 S/m at 100 °C and a fast discharge time (∼0.18 μs) in x = 0.1. Our findings in this work suggest that the obtained ceramics system might be a promising candidate for pulsed power technology.

A core–shell mixing technique was utilized to modify the Ba0.4Sr0.6TiO3 (BST)particles in order to obtain the fine-crystalline Ba0.4Sr0.6TiO3 ceramics and improve ceramics energy storage capability. Coating layers of (9B2O3–13Al2O3–78SiO2, mol%) (BAS)were deposited onto Ba0.4Sr0.6TiO3 nanoparticles by a sol-precipitation method. The microstructures, phase composition and dielectric properties were investigated. And fine-crystalline BST ceramics with an average grain size below 150 nm by coating BAS has been prepared. The dielectric breakdown strength and energy storage density significantly improved due to the addition of BAS. The maximum energy storage density obtained from coating 3 wt% BAS was 1.8 J/cm3 at 410 kV/cm, which was higher than pure BST ceramics. Thus, the core-shell architecture is an effective strategy to improve the energy storage performance.

The 0.6Bi0.5Na0.5TiO3–(0.4 − x)NaNbO3–xBa(Zr0.2Ti0.8)O3 (BNT–NN–BZT) ceramics were developed for application as high energy density capacitor by conventional solid-state reaction method, and their structure, dielectric and ferroelectric properties were investigated in detail. When BZT was introduced into the system, the crystal structure changed from tetragonal to pseudocubic. Temperature dependent dielectric permittivity showed a broad maximum in these pseudocubic ceramics, exhibitting distinct relaxor feature. The relaxor behavior was evaluated by modified Curie–Weiss and confirmed to be enhanced with increasing BZT content. Benefited from the relaxor feature, its dielectric constant and dielectric temperature stability were largely improved. The remanent polarization (Pr) and coercive electric field (Ec) decreased with high BZT content and the maximum polarization (Pm) improved as shown in ferroelectric hysteresis loops (P–E loops). The energy storage property was also improved with increasing BZT, the optimized energy storage property was obtained in x = 0.20 sample with W = 1.69 J/cm3 at 17.5 kV/mm, which was superior to many other ferroelectric relaxors, indicating that BNT–NN–BZT ceramics were promising candidates for temperature stable energy storage applications.

In this paper, 0.6(Na0.5Bi0.5)TiO3–0.4NaNbO3(0.6NBT–0.4NN) was synthesized by solid state reaction method. The homogenous green ceramic sheets with high density were produced by tape casting according to suitable casting parameters. Embryos of multilayered ceramic capacitors (MLCC) had been fabricated by punching, screen printing, stacking, laminating and cutting processes. And then after burning out and sintering at different conditions, the cross-sectional microstructures of components were compared. Differential scanning calorimetric analysis and the thermo-gravimetric analysis of green devices were carried out to analyze the effects of different sintering procedures on MLCCs. The dielectric properties and polarization loops of the MLCCs were investigated with dielectric constant (800–895), dielectric loss (0.004–0.007) and capacitance variation ΔC/C

Dense (1 − x )BaTiO 3− x (Na 1/4 Bi 3/4 )(Mg 1/4 Ti 3/4 )O 3 [(1 − x )BT– x NBMT] polycrystalline ceramics were prepared by solid-state reaction method. The detailed structure analysis was performed by X-ray diffraction (XRD) and Raman spectroscopy, confirming that the Ba and Ti sites were partially replaced by Na + /Bi 3+ and Mg 2+ ions, respectively. An obvious structural variation from tetragonal to pseudocubic was observed for sample with x = 0.08–0.12. The lattice parameter for sample with x ≥ 0.12 decreased linearly with x value. Three changing modes in frequency, width and intensity were observed with x value in the Raman spectra, indicating intense changes of local structure, accounting for evolved dielectric and ferroelectric macroscopic properties. The subgrain microstructures were observed by conventional transmission electron microscopy (TEM) imaging with an energy-dispersive X-ray spectroscopy (EDS) attachment. A large number of core–shell grains were detected by TEM dark field, for x = 0.20, which were attributed to the dissolution–precipitation mechanism. In this present study, (1 − x )BT– x NBMT ceramics are considered promising for high temperature capacitor applications.

A new energy-storage ceramic system based on (1 − x)(Bi0.5Na0.5TiO3–BaTiO3)–xNaTaO3 ((1 − x)(BNT–BT)–xNT) is reported in this study. XRD refinement indicated a composition induced rhombohedral to tetragonal phase transition. All the samples exhibited a dense microstructure with an average grain size of 1.2–1.9 μm. The introduction of NT greatly improved the temperature stability of the dielectric properties for the BNT–BT system. For compositions x = 0.03–0.15, the working temperature range spanned over 260 °C satisfying TCC150 °C ≤ ±15%. The electric conductivity as a function of frequency followed the double power law. In the temperature region of 325–500 °C, the activation energy of DC conduction ranged from 1.47 eV to 1.71 eV, indicating intrinsic band-type electronic conduction. The optimum energy-storage properties were obtained in 0.90(BNT–BT)–0.10NT with an energy-storage density of 1.2 J cm−3 and energy-storage efficiency of 74.8% at 10 kV mm−1. The results demonstrate that (1 − x)(BNT–BT)–xNT ceramics are promising candidates for high-temperature energy-storage applications.

The typical “core–shell” structure in BT ceramics can easily obtain double dielectric anomalies, which greatly improve the dielectric temperature stability for multilayer ceramic capacitors. In this paper, BaTiO3 particles were coated with 0.3BiAlO3–0.7BaTiO3 shell [xBT@(0.3BA–0.7BT)] by a sol–gel method. Core–shell structure was proved to exist in ceramic grains by transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). High-temperature X9R dielectrics were obtained when x=0.3 and 0.2, with a high dielectric constant (~1200) and low dielectric loss (

Sr 0.9775 Sm 0.015 TiO 3 ceramics with giant permittivity of about 40,000 and low dielectric loss of 0.0068 measured at 25 °C and 1 kHz were obtained by sintering the ceramics in N 2 at 1500 °C. The surface structure was analyzed by XPS measurement, which implied that a large number of Ti 3+ ions existed in the Sr 0.9775 Sm 0.015 TiO 3 ceramics sintered in N 2 . The results indicated that making the oxygen vacancies fully ionized by N 2 sintering could increase the permittivity and decrease the dielectric loss effectively.

Microstructural effects on the microwave dielectric properties of (Ba0.4Sr0.6)TiO3 (BST) polycrystalline ceramics were investigated, focusing on the grain size. Sintering temperatures between 1350°C and 1500°C have a strong effect on the permittivity (880

The bulk BiFeO3–BaTiO3 system has been studied as a potential lead-free high-temperature piezoelectric material. It is found that the multivalency manganese-doped 0.8BiFeO3–0.2BaTiO3 ceramics exhibit the coexistence of tetragonal and rhombohedral phases, whereas Mn doping improves the resistivity and exhibits hard characteristic. The optimal properties were obtained at 0.12 wt% Mn addition exhibiting Tc ˜ 637°C. The increase of Tc in Mn-modified compositions can be ascribed to the appearance of internal electric bias field by acceptor doping. The combination of good electrical properties and high Tc makes these ceramics suitable for elevated temperature piezoelectric devices.

A lead-free ceramics (1 − x)(0.84Na0.5Bi0.5TiO3–0.16K0.5Bi0.5TiO3)–xK0.5Na0.5NbO3 (x = 0, 0.03, 0.06, 0.09, 0.12, 0.15) for energy-storage application have been fabricated by conventional solid state method. All compositions were crystallized into perovskite solid solution structure ascertained by XRD. SEM micrograph revealed that homogeneous grain could be obtained by addition of appropriate K0.5Na0.5NbO3 (KNN). The depolarization temperature (Td) decreased significantly from 140 to 70 °C, while the maximum dielectric constant temperature (Tm) reduced slightly with increasing KNN. And the addition of KNN improved the energy-storage properties significantly by weakening the ferroelectricity of Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 (NBT–KBT) ceramics. When x = 0.09, the highest energy-storage density (W = 1.51 J/cm3) and energy efficiency (η = 65.0 %) were obtained at room temperature. Besides, the temperature stability of energy-storage density could satisfy ΔW/W100°C ≤ ±20 % when the addition of KNN was over 0.09 from 20 to 150 °C.

Based on (1 − x)(0.92Bi0.5Na0.5TiO3–0.08BaTiO3)–xNa0.73Bi0.09NbO3 ((1 − x)BNTBT–xNBN) lead-free ternary solid solution, a new energy-storage ceramic system was prepared and firstly reported in this study. The solid solubility of no more than 10 mol% for NBN was revealed by XRD characterization. Growing grains up to ~1.6 μm grain size and obviously broadened er versus T response were observed with increasing NBN from 10 to 40 mol%, indicating the greatly improved dielectric temperature stability. For sample with x = 0.20, optimized energy-storage properties with W = 1.36 J/cm3 and η = 73.9 % were achieved, together with a wide temperature range of −12 to 300 °C with ∣TCC∣ ≤ 15 %, showing potential for high temperature energy-storage applications.

0.85 Ba(Ti0.96Zr0.04)O3–0.15 Bi(Mg0.5Ti0.5)O3 relaxor ferroelectric ceramic samples were synthesized through traditional solid state reaction method. The asymmetric single peak of (200) at 45° was revealed by XRD measurement, combined with diffuse phase transition peaks in dielectric-temperature spectrum and a slim but discernible hysteresis loop, which proved the existence of the polar nano-regions (PNRs) in paraelectric matrix of the sample. The investigation of dielectric response of the ceramic samples under electric field (changing field magnitude and field history) was employed to analysize the evolution of PNRs. Electric field dependence of dielectric constant was obtained both by small signal bias electric field measurement and differential calculation from P–E curves, they all reached the maximum value firstly at the critical electric field and then decreased with the continuous increasing of electric field, instead of decreasing directly. However, the value of dielectric constant and critical field of bias electric field measurement was hysteretic electrically to those of differential calculation from P–E curves. Both the glassy model and macro–micro theory model were employed to explain and explore the evolution of PNRs, though from different perspective.

x BiAlO 3 –(1 − x )BaTiO 3 [ x BA–(1 − x )BT] polycrystalline ceramics were prepared by solid-state reaction method and sol–gel method, respectively. The ceramics were in tetragonal phase when x ≤ 0.1, transformed to pseudocubic at x > 0.1. The temperature stability of the dielectric constant for BA–BT was improved with BA contents increasing. Of particular interest was that the ceramics prepared by sol–gel method had less secondary phase, exhibiting much improved dielectric behavior. Among them, 0.3BA–0.7BT met the requirement of capacitance variation (Δ C / C ≤ ±15%) in the temperature range of −55 to 440 °C with moderate dielectric constant ( ɛ = 660) and low dielectric loss (tan δ = 1.2%) at room temperature (1 kHz). Nb-doped 0.2BA–0.8BT ceramics were investigated to improve the dielectric temperature stability at high-temperature end. It is found that all samples with 0.01–0.04 mol Nb addition satisfied the X8R specification.

Microwave-sintering (MWS) technique was employed to fabricate dense (Ba0.4Sr0.6)TiO3 (BST) ceramics. With respect to the high dielectric loss at room temperature, induced by the formation of oxygen defects during the MWS under vacuum atmosphere (−60 kPa), the as-sintered samples were thermally annealed in air to reduce tanδ and recover the insulating performance. Accompanied by the decreased tanδ, the energy storage properties for annealed MWS BST were optimized, with increasing energy density (γ) from 0.77 to 1.15 J/cm3 and energy efficiency (η) from 60% to 82%. The lower oxygen vacancy concentrations were believed to account for the enhanced insulating characteristics of grain boundaries and contribute to the improved properties after annealing. Electrical characterization of grain and grain boundary by impedance spectroscopy demonstrated that the annealing preferentially modified the grain boundary. In addition, resistances extracted from the high temperature impedance analysis were found to be inadequate for evaluating the electrical characteristics of materials affected by extrinsic mechanisms, such as the interfacial polarization. For comparison, annealing effect on energy storage properties were also discussed for conventionally sintered BST.

The effects of TiO 2 additives on microstructure and microwave dielectric properties of α -CaSiO 3 –2 wt%Al 2 O 3 ceramics have been investigated in detail. Specifically, the TiO 2 addition results in the presence of two distinct phases, e.g. CaTiO 3 and CaTiSiO 5 , which can inhibit the growth of α -CaSiO 3 grains by surrounding their boundaries and also improve the bulk density of α -CaSiO 3 –2 wt%Al 2 O 3 ceramics. However, the TiO 2 addition undermines the microwave dielectric properties of the title ceramics because the derived phases of CaTiO 3 and CaTiSiO 5 have poor quality factor. The τ f value is strongly correlated to the compositions and can be controlled through the compositional ratio. The α -CaSiO 3 –2 wt%Al 2 O 3 ceramics containing 2.5 wt% of TiO 2 sintered at 1250 °C showed excellent microwave dielectric properties (e r =7.88, Q × f =24,412 GHz and τ f =−0.52 ppm/°C).

MgO-doped 0.97BaTiO 3 –0.03BiYO 3 (0.97BT–0.03BY) polycrystalline ceramics were prepared by the solid-state sintering method. Then the structural, dielectric and resistant properties were investigated as functions of MgO addition. Microstructure was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). The results show that Bi 3+ , Y 3+ and Mg 2+ ions exhibit nonuniform distribution behavior in BT–BY ceramics, demonstrating the existence of a “core–shell” structure, which plays important roles in the capacitance-temperature characteristics, where 0.97BT–0.03BY with the addition 2.2–2.8 at% MgO meets the Electronic Industries Association (EIA) X8R (−55 to 150 °C, ΔC / C 25 °C =±15% or less) specification. Moreover, the fine-grained samples with core–shell structure show much higher bulk resistance than the coarse-grained samples over the studied temperature range, which is attributed to the higher proportion of grain boundaries and the lower concentration of the effective acceptor.

We investigated microstructures and energy storage properties of SiO 2 -coated BaTiO 3 ceramics that were prepared by the so-called Stober process. The thickness of coating layer of BaTiO 3 powders could be effectively controlled by the silica content. It could be observed that the secondary phases Ba 2 TiSi 2 O 8 appeared in the coated BaTiO 3 ceramics due to the interdiffusion reactions between SiO 2 and BaTiO 3 components under sintering. BaTiO 3 cores in the coated ceramics remained up to the original grain size indicating the coating layer as an inhibitor. The results showed that both breakdown strength and energy density were improved apparently. The homogeneity of silica coating in the ceramics should dominate contribution to breakdown strength, which can reduce the weak-point breakdown under high electric field. The optimized composition for BaTiO 3 ceramic coated with 2.0 wt% SiO 2 showed the maximum energy storage density of 1.2 J/cm 3 with energy storage efficiency of 53.8%, which is about three times higher than that of pure BaTiO 3 (0.37 J/cm 3 ).

The microstructure, phase structure, ferroelectric, and dielectric properties of (1−x)Bi0.5Na0.5TiO3-xNaNbO3 [(1−x)BNT-xNN] ceramics conventionally sintered in the temperature range of 1080°C–1120°C were investigated as a candidate for capacitor dielectrics with wide temperature stability. Perovskite phase with no secondary impurity was observed by XRD measurement. With increasing NN content, (1−x)BNT-xNN was found to gradually transform from ferroelectric (x = 0–0.05) to relaxor (x = 0.10–0.20) and then to paraelectric state (x = 0.25–0.35) at room temperature, indicated by P–I–E loops analysis, associated with greatly enhanced dielectric temperature stability. For the samples with x = 0.25–0.35, the temperature coefficient of capacitance (TCC) was found

(1 − x)BaTiO3–xBi(Y0.5Yb0.5)O3 (BT–BYYb, x = 0.01–0.12) ceramics were prepared via solid-state processing techniques. The structure, dielectric and impedance properties of (1 − x)BT–xBYYb ceramics are studied. The studies show that the ceramics are in tetragonal phase when x ≤ 0.07, transform to pseudocubic phase at x ≥ 0.08. The grain growth is obviously suppressed for (1 − x)BT–xBYYb samples with x value. Dielectric properties are depressed and dielectric peaks are broadened with x. Tm first increases and then decreases. BT–BYYb system exhibits diffused phase transition and good temperature stability, which is due to the increased cation disorder, forming the local difference of the polar region due to the size and charge difference and inducing many different regions with different Curie points. The samples can meet the temperature requirements of X8R characteristics at 1 kHz with: e ~ 1330, tanδ ~ 0.0076, |△C/C| ≤ ±15 % (−55 to 150 °C) for x = 0.11 and e ~ 1032, tanδ ~ 0.012, |△C/C| ≤ ±15 % (−55 to 170 °C) for x = 0.12, respectively. The activation energy of the bulk material obtained from conduction and relaxation first increases and then decreases with increasing BYYb concentration. The different activation energy indicates various mechanisms are involved in the conduction and relaxation process, which may be due to the mixed conduction or doubly ionized oxygen and thermal motions of titanium ions (Ti4+) or doubly ionized oxygen, respectively.

The energy storage properties of Ca-doped (Sr, Ca)TiO3 (SCT) paraelectric ceramics have been intensively investigated by traditional solid state sintering method. Phase structures and morphology were detected by the X-ray diffraction and SEM, respectively. The electric field strength dependence of polarization was measured and employed to calculate the energy storage density. The doped SCT ceramics exhibit high permittivity, low loss, and higher breakdown strength. At 333 kV/cm electric field strength, the energy storage density of the 2 mol % Ca-doped SrTiO3 ceramics with fine grain can achieve 1.95 J/cm3, which is 2.8 times of pure SrTiO3 in the literature, and its energy storage efficiency reaches 72.3 %. Therefore, the SCT ceramics might be a kind of promising energy storage dielectric material.

(1 − x)BNTBT-xNN ceramics were prepared by conventional solid state reaction method. X-ray fluorescence analysis shows that the volatilization of Na element occurs during sintering process, the resulted concentration variation of V ′ Na − V O − V ′ Na defect dipoles facilitate the grain growth. XRD analysis and dielectric properties analysis indicate that rhombohedral polar phase and tetragonal weakly polar phase coexist in BNTBT ceramics at room temperature. By increasing the NN amount, the rhombohedral polar phase content sharply decreases, leading to a smaller remnant polarization. The dielectric anomaly corresponding to the depolarization temperature disappears from the temperature range investigated. According to the XRD results, the amount of tetragonal weakly polar phase decreases with increasing NN content and the structure evolves toward a pseudocubic symmetry. The phase structure change results in more slim P–E loops. The optimum energy storage properties was obtained for the composition of x = 0.10, with energy storage density of 0.71 J/cm3 at 7 kV/mm and a good temperature stability around 25–150 °C.