Lead-free Ceramics Research Articles

Innovative Design of BNKT-xSLZT Ceramics: Maximizing the Polarization Difference for Enhanced Energy Storage.

Lead-free relaxor ferroelectric ceramics with outstanding energy-storage (ES) density (Wrec) and high ES efficiency (η) are crucial for advanced pulse-power capacitors. This study introduces a strategic approach to maximizing the polarization difference (ΔP) by inducing a transition from the ferroelectric phase to the ergodic relaxor (ER) phase. By employing this strategy, a series of ceramics, (1 - x)(Bi0.5Na0.4K0.1)TiO3-x(Sr0.85La0.1)(Zr0.5Ti0.5)O3 (BNKT-xSLZT), with varying SLZT content (x = 0.05, 0.10, 0.15, and 0.20), were designed. The addition of SLZT enhances cationic disorder, induces vacancies at A sites, and disrupts long-range ferroelectric order, facilitating the formation of polar nanoregions and enhancing relaxor ferroelectric behavior. Furthermore, a viscous polymer process (VPP) technology is employed to optimize the ceramics' structure, aiming to increase the breakdown strength (Eb) and enhance ΔP. Ultimately, enhanced ES performance is demonstrated in BNKT-0.15SLZTVPP, achieving a remarkable Wrec of 6.85 J/cm3 and η of 84% under 470 kV/cm. This composition demonstrates excellent stability with minimal variations in Wrec (3.0%) and η (4.4%) over the temperature range of 20-110 °C. Additionally, BNKT-0.15SLZTVPP exhibits exceptional pulse charge-discharge properties, featuring a high discharge density of 3.72 J/cm3, a large power density of 164.2 MW/cm3, and a short discharge time (t0.9) of 193 ns under 300 kV/cm. The study validates the practicality of BNKT-0.15SLZTVPP for pulse capacitors and underscores the potential to enhance ES performance through A-site donor doping and VPP technology. This work provides a comprehensive understanding of the interplay among composition, structure, and ES properties in lead-free relaxor dielectric ceramics, laying the groundwork for innovative advancements in the field.

Enhanced relaxation behavior and energy storage properties in (Al0.5Nb0.5)4+ complex ions modified Na0.5Bi0.5TiO3-based ceramics under low electric field

In recent decades, high polarization and low residual polarization lead-free relaxor ferroelectric ceramics have attracted lots of focus due to their great potential in dielectric capacitors for energy storage. In this work, Na0.35Bi0.35Sr0.3Ti(1-x)(Al0.5Nb0.5)xO3 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05) lead-free ceramics have been fabricated by the traditional solid-stated reaction method. By doping (Al0.5Nb0.5)4+ complex ions into 0.7Na0.5Bi0.5TiO3-0.3SrTiO3, pure perovskite phases and reduced grain sizes are obtained. Increasing the AN concentration not only moves the Ts toward the lower temperature, but also keeps the permittivity at a high average value, which shows a good thermal stability of the dielectric properties (εr150°C ∼ 3903 ± 15% in the range of 42–232 °C). Furthermore, Na0.35Bi0.35Sr0.3Ti(1-x)(Al0.5Nb0.5)xO3 presents a reduced residual polarization due to the improved relaxor behavior, and achieves a moderate energy storage property at low electric field of 155 kV/cm (when x = 0.04 Wrec is 1.85 J/cm3, and η is 89.0%). More importantly, the ceramic also possesses great frequency, temperature and cycle stability. Hence, the (Al0.5Nb0.5)4+ modified 0.7Na0.5Bi0.5TiO3-0.3SrTiO3 ceramics have exhibited a potential application in dielectric capacitors for energy storage.

Structural phase coexistence enhances the energy storage density of (Bi0.5Na0.5)0.8Ba0.2Ti1-ySnyO3 lead-free ceramics

In the present study, BaSnO3 was introduced into polycrystalline NBT-BT ferroelectric ceramics and conducted a comprehensive investigation into the structural, dielectric, ferroelectric, and energy storage characteristics of the (Bi0.5Na0.5)0.8Ba0.2Ti1-ySnyO3 (BNBTS) ceramics. The coexistence of structural phases P4mm and Amm2 was observed through Rietveld refinement and also confirmed by Raman analysis. The formation energy decreases with an increase in substitution concentration favouring the formation of the orthorhombic phase. The SEM analysis revealed a denser microstructure characterised by smaller grain sizes, which favourably enhances energy storage density. Furthermore, Raman spectroscopic analysis unveiled a softening of Ti–O bonds, indicating the emergence of macroscopic relaxor behaviour. Dielectric studies provided evidence of a transition from ferroelectric to relaxor behaviour, an observation further confirmed by P-E loop measurements. This transition can be linked to the partial substitution of Sn4+ ions for Ti4+ ions, disrupting the ferroelectric long-range order within the matrix phase. Notably, the polarization-electric field (P-E) loop of BNBTS2 ceramics exhibited a substantial value of polarization (Ps) 30 μC/cm2 with a reduced value of remnant polarization (Pr) 2.29 μC/cm2. These characteristics contributed to the achievement of higher energy recovery (Wrec) and lower energy loss (Wloss) values, measuring 1.184 J/cm3 and 0.142 J/cm3, respectively, with a notable efficiency of 88.8%. Consequently, the system of ternary ceramics demonstrates promise as a potential option for energy storage ceramics among NBT-BT-based materials.

Enhanced dielectric, ferroelectric and piezoelectric properties of lead-free (Ba,Ca)(Sn,Ti)O3 ceramics by optimisation of sintering temperature

Lead-zirconate-titanate [Pb(Zr,Ti)O3 PZT] crystals possess superior ferroelectric, dielectric and piezoelectric properties. However, due to the toxicity of lead there is a demand for lead-free alternatives. In the present work, we focus on the production of the lead-free (Ba,Ca)(Sn,Ti)O3 (BCST) ceramics via solid-state synthesis method. BCST ceramics calcined at 1050°C, 1100°C, 1150°C, 1200°C and 1250°C were characterized using XRD analysis which showed that at temperatures above 1150°C the structure was free from impurities. Rietveld refinements confirmed a tetragonal structure with P4mm space group for the material calcined at 1150°C. Scanning electron microscopy image analysis of samples sintered at 1200°C, 1250°C and 1300°C showed an increase in grain size and density with temperature. The material sintered at 1300°C had a higher dielectric constant compared to other ceramics. A larger grain size facilitated high ferroelectric polarisation (3.38 μC/cm2), dielectric constant (6100) and d33 piezoelectric coefficient (236 pC/N) for the ceramics. This study demonstrates the potential for using lead-free BCST ceramics for device applications, such as piezoelectric actuators, transducers and ultrasonic motors.

Piezoelectric response and figure of merit assessment in lead-free (Ba1-xSrx)(Zr0.025Ti0.975)O3 ceramics with low-level Sr2+ substitutions

This study investigates the effects of low-level Sr2+ substitutions on the microstructures and electrical properties of BSZT ceramics with formula (Ba1-xSrx)(Zr0.025Ti0.975)O3. The ability of BSZT ceramics to convert energy is assessed based on the piezoelectric coefficient, d33 associated with the figure of merit (FOM). BSZT ceramics with 0.00 ≤ x ≤ 0.10 were sintered at 1350 °C for 2 h. The XRD measurement confirmed the formation of a single-crystalline phase in all ceramics. All ceramics stabilized in tetragonal crystal structures with progressive decline in tetragonality. It was found that the ceramic with low-level Sr2+ substitutions demonstrated excellent dielectric, piezoelectric and ferroelectric behaviours before gradually deteriorated at higher contents. Systematic deviation of Sr2+ atomic percentage signified broad dielectric curves compared to pristine Ba(Zr0.025Ti0.975)O3. A significant increase of remnant polarization, Pr value (11.21 ± 0.12 μC/cm2) was recorded when x = 0.02, in line with its highest as-sintered density and tetragonality. High d33 and low ε33 values contributed to an optimum value of piezoelectric voltage, g33 coefficient. Consequently, a high FOM comparable to PZT was obtained. The current work successfully demonstrated the preparation of lead-free ceramics based on BaTiO3 with great potential for energy conversion applications.

Enhanced energy storage properties of silver niobate antiferroelectric ceramics with A-site Eu3+ substitution and their structural origin

AgNbO3 (AN)-based lead-free antiferroelectric ceramics are widely studied for their use as dielectric capacitor materials. In this study, Eu3+-doped AN ceramics were prepared and the results show that Eu3+ diffused into the AN lattice. The ceramics were formed by M1 and M2 phases coexisting at room temperature, as distinct from the M1 (M: monoclinic) phase of pure AN. Electrical properties and structural characterization showed that the antiferroelectric stability of the ceramics increases with the increase in Eu3+ levels. At room temperature, Ag0.94Eu0.02NbO3 ceramic exhibited a good energy storage density of 5.3 J/cm3 and a high efficiency of 71.9%. When the temperature rises from room temperature to 140 °C, the efficiency of the sample decreases from 80.4% to 67.1% and Wr decreases from 2.1 to 2.0 J/cm3, which indicates that the sample has good temperature stability. The time constant (t0.9) of this sample was less than 60 ns and the power density (PD) was 51.3 MW/cm3, indicating excellent charge–discharge capabilities. This novel ceramic is expected to be used as a new dielectric capacitor material for pulsed power supplies.

Structural and electrical investigation of rare-earth doped lead-free SrBi4Ti4O15 ceramics

Structural and electrical investigation of rare-earth doped lead-free SrBi4Ti4O15 ceramics

High energy storage performance of (1-x)Ba0.5Sr0.5TiO3-xK0.5Na0.5NbO3 ceramics via a combined strategy of fine grains and multiphase polar nanoregions

Electrostatic dielectric capacitors have received great attention due to their ultrafast charging-discharging speed and ultrahigh power density. However, the low energy storage density and efficiency are the main obstacles to their practical applications. In this work, solid solution relaxor ceramics with different proportions of lead-free ferroelectrics Ba0.5Sr0.5TiO3 (BST) and K0.5Na0.5NbO3 (KNN) were prepared. Superior energy storage performance was achieved in the 0.7BST-0.3KNN ceramics with a breakdown strength (Eb) of 510 kV/cm, a recoverable energy storage density (Wrec) of 4.10 J/cm3, and an energy storage efficiency (η) of 80 %, which was fairly stable over the temperature range of 30–100 °C. Since multiple cations with different valence and radius coexist on the equivalent sites (A or B sites) of the solid solutions, the chemical disorder and the corresponding lattice distortion induced the coexistence of cubic, tetragonal, and orthorhombic phases, as well as the appearance of the multiphase polar nanoregions (PNRs), making the ferroelectric hysteresis loops linear. At the same time, ultrafine grains in the ceramics greatly improved the Eb. For achieving excellent energy storage performance, this work demonstrates a potential candidate of (1-x)BST-xKNN lead-free solid solution ceramics and a combined strategy of fine grains and multiphase PNRs.

Enhanced soft piezoelectric properties of Sb2O3 doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 materials

In this paper, we have studied the soft piezoelectric properties of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 doped with Sb2O3. The optimal piezoelectric charge constant and dielectric permittivity of the calcined and sintered 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 were determined by varying the Sb2O3 content. The mol% of Sb2O3 was set to 0, 0.05, 0.1, 0.15, and 0.2, and the doped ceramics were sintered at a temperature of 1475 °C. The piezoelectric charge constant d33, electromechanical coupling coefficient kp, and dielectric permittivity εr of the doped ceramics increased with the increasing Sb2O3 content, whereas their Curie temperature Tc slightly decreased. At 0.1 mol% of Sb2O3, the highest piezoelectric charge constant, electromechanical coupling coefficient, and dielectric permittivity values were obtained. Although the Curie temperature was slightly lowered, the dielectric permittivity improved. 0.5BZT-0.5BCT doped with Sb2O3 exhibited a high remnant polarization Pr even when a weak coercive electric field Ec was applied, resulting in an easy polarization. It can be seen that the improved electrical properties and the behavior of the P-E hysteresis loop through the dopant addition of Sb2O3 are close to the soft piezoelectric characteristics. Thus, the synthesized lead-free and Sb2O3-doped ceramics, with excellent piezoelectric properties and depolarization behaviors, are expected to replace lead-based ceramics and will be useful in energy converters, such as piezoelectric transformers.

Engineering Phase Separation in Niobate Glass through Ab Initio Molecular Dynamics for Enhanced Energy Storage Performance and Unprecedented Thermal Stability in Niobate-Based Glass Ceramics.

The advancement of lead-free glass ceramics (GCs) possessing appropriate energy storage characteristics is crucial for the renewable energy and electronics industry. In this study, we synthesized lead-free GCs predominantly composed of the tungsten bronze phase, Ba3.3Nb10O28.3. Ab initio molecular dynamics initially reveal nonuniform distribution within the Ba/Nb-O regions in niobite glassy melts, offering valuable insights for the subsequent crystallization process. The proposal of a B-site engineering strategy is suggested, which entails the concurrent reduction of grain size and augmentation of the band gap in tungsten bronze GCs doped with Ta. This approach results in a substantial enhancement of the dielectric breakdown strength (BDS). Phase-field simulations have indicated that the refinement of grain sizes plays a pivotal role in augmenting the local electric field distribution and breakdown path, thereby contributing to the enhancement of BDS. As a consequence of these modifications, a notably high recoverable energy density (Wrec) of 5.23 J/cm3 can be achieved, accompanied by an ultrahigh efficiency (η) of 94%, and superior thermal stability in energy storage. These outcomes are particularly evident in the case of 2 mol % Ta2O5-doped P2O5-K2O-BaO-Bi2O3-TeO2-Nb2O5 (PKBBTN-T) GCs, where the Wrec and η can be determined to be 2.87 ± 3% J/cm3 and 95.46 ± 4%, respectively, over a temperature range spanning from 20 to 150 °C. Additionally, this specimen exhibits an exceptionally high discharge energy density (Wdis) of 4.01 J/cm3. This comprehensive investigation, comprising experimental and theoretical analyses, establishes an effective pathway and paradigm for the development of dielectric materials with ultrahigh energy storage properties.

Enhanced temperature stability in AgNbO3 lead-free antiferroelectric ceramics through texture engineering

Lead-free dielectric materials with excellent temperature stability are critical to meet ever-increasing demands for practical energy storage applications. Herein, good temperature stability was achieved in AgNbO3 (AN) antiferroelectric ceramics through texture engineering by using NaNbO3 (NN) as template. The 3% <001>-oriented NN modified AN (AN-3NN) textured ceramic showed an optimized grain orientation degree of ∼97% by using a templated grain growth technique. Interestingly, the AN-3NN textured ceramic possessed excellent temperature stability for both Wrec and energy storage efficiency (η) with respective variations below 0.7% and 0.6% over a temperature range of 20–130 ºC, significantly higher than the non-textured one with respective variations around 7% and 14%. The increased grain orientation and decreased defect concentration for texture engineering contribute to the improved thermal stability.

Stable macro-performance at extreme cold region for KNN-based ceramics with modified phase boundary

High performance with good stability is important for practical application of electronic devices. As abundant researches related to the stability at room temperature and above have been adopted, the characteristic at extreme cold region is little concentrated on, impeding the development of plateau section. Herein, the stability of electrical properties is emphasized on at extreme cold region for the KNN ceramics with polycrystal phase boundary. Rhombohedral-orthorhombic (R-O) phase boundary is successfully formed from extreme cold region to room temperature. Notably, stable polarization is revealed with maintained R-O phase boundary. Little changed piezoelectric response is gained with modified R-O phase boundary, indicating that abundant O and lesser R phases coexistence is beneficial of improving temperature stability at extreme cold region. Thus, this work demonstrates a tool for optimizing performance at extreme cold region of lead-free ceramics, accelerating the application of electronic devices at plateau-climate regions.

Enhanced dielectric energy storage performance of Na0.5Bi0.5TiO3-LiTaO3-based lead-free relaxor ferroelectric ceramics through domain structural regulation and improved densification

Ceramic materials with relaxor dielectric properties, expressed as (1-x)(0.94Na0.5Bi0.5TiO3-0.06LiTaO3)-xCaTiO3 [(1-x)(NBT-LT)-xCT] with x values of 0.12, 0.15, 0.18, and 0.21, were synthesized through an A-site doping method to enhance energy storage capabilities. The linear dielectric CaTiO3 was chosen as the acceptor additive, and ceramic samples were prepared using conventional solid-phase and molding techniques. A comprehensive investigation evaluated the influence of different CT concentrations on the phase and energy storage/release characteristics of NBT-LT.Optimal performance was notably achieved with a 15% CT doping concentration, resulting in Wrec and η values of 2.16J/cm³ and 70%, respectively, for a 100 μm thick sample under a 210kV/cm voltage. When the film was rolled to a 60 μm thickness, the voltage strength increased to 330kV/cm, leading to enhanced Wrec (5.33J/cm³) and η (80%). Within the temperature range of 30 °C to 150 °C, only a marginal change in Wrec (less than 10%) was observed. Frequency conversion tests across the 1Hz to 100Hz range demonstrated the material's relative stability, with Wrec exhibiting minimal fluctuations. These findings emphasize the outstanding temperature and frequency stability of the material. During discharge, the material displayed a power density of up to 152MW/cm³, coupled with a discharge time of 0.3 μs, showcasing remarkable pulse discharge capabilities. The experimental results affirm the promising potential of (NBT-LT)-0.15CT lead-free relaxor ferroelectric ceramics for application in commercial capacitors.

Advancing energy storage capabilities in 0.7BNST(1-x)-0.3BLMNx lead-free dielectric ceramic materials

Lead-free ferroelectric ceramics with a composition of 0.7(Bi0.5Na0.5)0.7Sr0.3Ti(1-x)O3-0.3Ba0.94La0.04(Mg1/3Nb2/3)xO3 (abbreviated as 0.7BNST(1-x)-0.3BL(MN)x, 0 ≤ x ≤ 0.12) were prepared using solid-phase sintering method, involving co-substituting at A and B sites. High recoverable energy density (Wrec) of 3.54 J/cm3 and energy efficiency (η) 85.49% are achieved at an electric field of 270 kV/cm. Furthermore, these ceramics exhibited excellent temperature and cycle stability at 120 kV/cm (within 25 °C–150 °C, Wrec fluctuation range <14 %; under 1∼106 cycles, the Wrec fluctuation range <5 %). In terms of dielectric performance, they exhibited a high dielectric constant (εr∼4540), an extremely low dielectric loss tanδ of <0.04 (30 °C–300 °C), and good temperature stability with Δε/ε150 °C ≤ ±15 % (−19.5 °C–233.4 °C). During the charging and discharging process, these ceramics demonstrated a high energy density (Wd) of 1.2 J/cm3, a power density (PD) of 61.7 MW/cm3, and an extremely short discharge time (t0.9) of approximately ∼0.11 μs＀ This study has improved the dielectric energy storage performance of BNT-based lead-free piezoelectric ceramics, making them suitable for use in pulse power devices.

Fulfilling X9R specification in CeO2 modified BNBST-based relaxor ferroelectric energy storage ceramic capacitors

Future low-voltage driven capacitor devices are appealed to employ the eco-friendly ceramics featured with high-stable dielectric energy storage capabilities. Herein, the dielectric energy storage properties of (Bi0.5Na0.5)0.65(Ba0.3Sr0.7)0.35(Ti0.98Ce0.02)O3+8 wt% K0.5Na0.5NbO3+x wt% CeO2 (BNBSTCK + Cx) lead-free relaxor ferroelectric ceramics were comprehensively investigated. By maintaining the relaxor ferroelectric phases near room temperature and disrupting the ferroelectric long-range order via CeO2 additive, the EIA X9R specification was fulfilled at the best composition of x = 8 over a wide range of −74∼208 °C with a relatively high dielectric constant εr = 904 and low loss tanδ = 10−3 (@25 °C & 1 kHz). Meanwhile, the good recoverable energy storage density Wrec = 0.77 J/cm3 and high efficiency η = 91.6% were achieved only at a low electric field of 95 kV/cm. Furthermore, these ceramics exhibited exceptional frequency and cycle dependent energy storage stability, which could guide the design ideas of long-life X9R ceramic capacitors suitable for high and low working temperature environments in low-voltage driven energy storage applications.

Enhanced energy storage performance of Na0.5Bi0.5TiO3-based relaxor ferroelectric ceramics by synergistic optimization strategies

Despite the fact that Na0.5Bi0.5TiO3 (NBT) based lead-free ceramics have attracted widespread interest due to their various advantages, their lower recoverable energy storage density (Wrec) and energy storage efficiency (η) limit their development in pulsed power capacitors. In this work, we propose a synergistic optimization strategy to enhance the energy storage performance of 0.65Na0.5Bi0.5TiO3-0.35SrTiO3(NBST) based lead-free ceramics by introducing Bi0.8La0.2(Ni0.5Zr0.5)O3 (BLNZ) and employing viscous polymer process (VPP). The former converts the macroscopic domains into microscopic domains, limiting the polarization response hysteresis to give a large Pm–Pr. The latter reduces the thickness and porosity of the samples, resulting in a substantial increase in breakdown strength. Ultimately, by stepwise optimization of this strategy, the x = 0.15 ceramic by VPP (0.15VPP) achieves excellent energy storage performance (Wrec = 7.6 J/cm3, η = 92%) under 620 kV/cm and reliable temperature stability from 20-140 °C. The combined excellent results of this study show that our synergistic optimization strategy can effectively enhance the energy storage performance of NBT-based dielectric ceramics and could be further extended to other ceramic materials for pulsed power capacitors.

Improving the Energy Storage Performance of Barium Titanate-Based Ceramics through the Addition of ZnO-Bi2O3-SiO2 Glass

Lead-free ceramics with excellent energy storage performance are important for high-power energy storage devices. In this study, 0.9BaTiO3-0.1Bi(Mg2/3Nb1/3)O3 (BT-BMN) ceramics with x wt% ZnO-Bi2O3-SiO2 (ZBS) (x = 2, 4, 6, 8, 10) glass additives were fabricated using the solid-state reaction method. X-ray diffraction (XRD) analysis revealed that the ZBS glass-added ceramics exhibited a perovskite structure, with the maximum relative density achieved at x = 6. The average grain size reduced obviously as the glass additive wt% increased. Also, the dielectric constant decreased and the breakdown strength increased with increases in the glass additives. The optimal energy storage density of 1.39 J/cm3 with an energy storage efficiency of 78.3% was obtained at x = 6 due to high maximum polarization and enhanced breakdown strength. The results demonstrate that this material is a potential candidate for high-pulse-power energy storage devices.

Achieving giant field-induced strain in BS-modified BNKT lead-free ferroelectric ceramics

Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BNT-BKT) binary systems with the morphotropic phase boundary (MPB) are promising candidates for piezoelectric actuators. However, pure BNT-BKT ceramics commonly exhibit unfavorable electric field-induced strain, which is insufficient to meet the requirements for actuator applications. Rare earth-containing dopants have been extensively explored to modify various materials due to their unique optical, magnetic, and electronic properties. Here, by introducing rare earth ion-containing dopants BiScO3 (BS), the electrical properties of Bi0.5(Na0.84K0.16)0.5TiO3 (BNKT) lead-free ferroelectric ceramics have been modified. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results suggest that the introduction of BS results in an increase in tetragonal (T) phases, reduced grain sizes, and uniform morphologies. Ferroelectric measurements demonstrate that the BS-containing ceramics show slimmer hysteresis loops. The BNKT-2BS ceramics show a noteworthy improvement in electric field-induced strain, with bipolar and monopolar strains of 0.58% and 0.68%, respectively, which are almost 4 times and 6 times higher than those of pure BNKT ceramics. Furthermore, the corresponding normalized strain (d33*) also achieves high values of 967 pm/V and 1133 pm/V, respectively. Temperature-dependent dielectric measurements reveal that BS-containing ceramics exhibit good relaxor characteristics with frequency dispersion and diffuse phase transitions. This study presents a sufficient and feasible strategy for the optimization of strain performance in large displacement actuator applications.

MnO2 doping enhances energy storage performances in lead-free BiFeO3-based ceramics

BiFeO3-based ferroelectric ceramics as promising candidates for energy storage devices have attracted a great deal of interest owing to the large ferroelectric polarization and high Curie temperature. However, the Bi volatilization induced oxygen vacancy and Fe2+/Fe3+ ionic hopping limit its energy storage performances (ESP). A charge compensated method by introducing multivalent oxide is proposed to inhibit the oxygen vacancy and Fe2+/Fe3+ ionic hopping, aiming to improve dielectric breakdown strength (BDS), polarization saturation and ESP. Here, we prepared a series of MnO2-modified Bi0.83Sm0.17Fe0.95Sc0.05O3-0.85BaTiO3-0.15Bi(Mg0.5Zr0.5)O3 [BSFS-BT-BMZ-x wt%MnO2] ceramics by traditional solid state sintering. It revealed that a large reversible energy storage density (Wrec) of ∼ 4.1 J/cm3 and a great efficiency (η) of ∼ 88% can be achieved at x = 2.1 ceramics. The improved ESP could be attributed mainly to the effective inhibition of Fe2+ by multi-fold valence states of Mn ions accompanying with the decreasing of oxygen vacancy and Fe3+/Fe2+ ionic hopping, leading to the refinement of grain size, and the enhancement of BDS and ferroelectric polarization. Moreover, the optimized ceramics exhibit the good frequency/thermal stability, excellent fatigue resistance and high powder density. These results demonstrate that a charge compensated method pays a route of improving ESP for dielectric ceramic capacitors.

Excellent energy storage properties in BNT-based relaxor ceramics via composition optimization strategy

In this work, lead-free energy storage ceramics, (1−x)(0.95Bi0.5Na0.5TiO3-0.05Ba0.85Ca0.15Zr0.1Ti0.9O3)-xSr0.7La0.2SnO3 (BNT-BZCT-xSLS, x = 0.05, 0.10, 0.15, and 0.20), were prepared. The crystal structure, microstructure, dielectric properties, ferroelectric properties, energy storage properties, and charge-discharge performance of BNT-BZCT-xSLS were systematically studied. Among the products, BNT-BZCT-0.15SLS exhibited the highest energy storage performances (W = 2.95 J/cm3, W rec = 2.09 J/cm3, and η = 71%) due to its dense microstructure, finer grain size, and improved relaxation. Furthermore, the BNT-BZCT-0.15SLS also showed an ultra-fast charge and discharge speed (t0.9 = 0.033 μs) and a large power density (P D = 28.0 MW/cm3).