| Home | E-Submission | Sitemap | Login | Contact Us |  
top_img
J. Korean Ceram. Soc. > Volume 56(1); 2019 > Article
Peddigari, Palneedi, Hwang, and Ryu: Linear and Nonlinear Dielectric Ceramics for High-Power Energy Storage Capacitor Applications

Abstract

Dielectric materials with inherently high power densities and fast discharge rates are particularly suitable for pulsed power capacitors. The ongoing multifaceted efforts on developing these capacitors are focused on improving their energy density and storage efficiency, as well as ensuring their reliable operation over long periods, including under harsh environments. This review article summarizes the studies that have been conducted to date on the development of high-performance dielectric ceramics for employment in pulsed power capacitors. The energy storage characteristics of various lead-based and lead-free ceramics belonging to linear and nonlinear dielectrics are discussed. Various strategies such as mechanical confinement, self-confinement, core-shell structuring, glass incorporation, chemical modifications, and special sintering routes have been adopted to tailor the electrical properties and energy storage performances of dielectric ceramics. In addition, this review article highlights the challenges and opportunities associated with the development of pulsed power capacitors.

1. Introduction

Capacitors are widely employed as passive components in many electronic devices. They are used for carrying out a host of functions such as pulse discharging, filtering, voltage smoothing, coupling, de-coupling, dc blocking, power conditioning, snubbing, electromagnetic interference suppression, and commutation in pulsed power and power electronics applications.1) The technology of capacitors as storage media for electrical energy dates back to the beginning of the 20th century. Through the various stages of development, different materials such as glass, paper, mica, lacquer, polymers, and ceramics have been utilized as capacitor elements.2) In a dielectric capacitor, the insulating material placed between two parallel conductive plates becomes polarized and stores electrical charge in proportion to the electric potential between its terminals (Fig. 1).
In the past two decades, lots of efforts have been made towards the development of energy storage technologies such as batteries, electrochemical capacitors, and dielectric capacitors to meet the requirement of on-demand utilization of the electricity generated from renewable energy sources. As indicated by the Ragone plot shown in Fig. 2(a), there are significant differences in the energy density and power density of these storage devices, which are attributed to the differences in their energy storage mechanisms and charge-discharge processes. In contrast to the other storage devices, dielectric capacitors can release the stored energy in an extremely short period of time (microseconds-milliseconds) and generate an intensely pulsed current or voltage, which make them suitable for applications in pulsed power electronic systems. Further, unlike the cases of electrochemical capacitors and batteries with liquid electrolytes and involving chemical reactions, dielectric capacitors exhibit superior thermal and mechanical stability and can be operated under higher voltages (several hundred to thousand volts) for longer durations.
In view of their potential applications in pulsed power electronics for use in various commercial, civilian, and military systems, as well as considering the significantly increasing number of publications on dielectric capacitors for energy storage applications in recent years (Fig. 2(b)), this area of research is currently one of the hot topics in the domain of energy storage technologies. The applications of dielectric capacitor-based pulsed power electronics include medical equipment (defibrillators, pacemakers, surgical lasers, X-ray units), scientific research (nuclear effects simulations, high-power accelerators, high-intensity magnetic field experiments), commercial systems (camera flash, food sterilization, metal forming, cable fault detection equipment, underground oil and gas exploration), energy systems (grid-connected photovoltaics and wind turbine generators, power grid fluctuation suppression, high-frequency inverters), transportation (hybrid electric vehicles, electric trains, electric aircrafts), avionics (space-shuttle power systems, rocket propulsion systems), military (active armors, electrochemical guns, radars, high-power microwave devices, ballistic missiles), etc.
Although dielectric capacitors possess high power densities with fast discharge rates, their energy density should be further increased to reduce the volume of the capacitors. Currently, linear dielectric polymer materials with low dielectric constants but high breakdown fields are employed in commercial pulsed power capacitors, exhibiting energy density < 5 J/cm3. To be competitive with supercapacitors, the dielectric capacitors should offer energy density > 30 J/cm3.3) Hence, much of the research on emerging dielectric materials is being carried out in pursuit of enhanced energy density, which would make the dielectric capacitors useful for an even wider variety of applications. The energy storage performance of these capacitors is evaluated in terms of energy density and storage efficiency, which are related to permittivity (ɛ) and polarization (P) of the dielectric material and the external applied field (E) (Fig. 1). For linear dielectrics with negligible loss, the energy density (U) can be expressed as U=12ɛ0ɛrE2, where ɛ0 and ɛr are the vacuum permittivity and relative permittivity, respectively. For nonlinear dielectrics, which exhibit some energy dissipation, the stored (or charge) energy density (Ust) and recoverable (or discharge) energy density (Urec) can be determined from the polarization-electric field (P-E) hysteresis measurements through the following equations:
(1)
Ust=0PmaxEdP
(2)
Urec=PrPmaxEdP
where Pr and Pmax are the remnant and maximum polarizations, respectively. The energy loss density (Uloss) is equal to the hysteresis loss, i.e., the area of the P-E loop. Accordingly, the energy storage efficiency of the capacitor is represented by the ratio between Urec and Ust as follows:
(3)
η=UrecUst=UrecUrec+Uloss
It can be concluded from the above equations that high values of permittivity, maximum (saturation) polarization, and breakdown strength (BDS) will lead to larger energy densities, while low dielectric/hysteresis losses and low remnant polarizations will facilitate greater energy storage efficiencies of dielectric materials. In addition, the material should possess low electronic/ionic conductivity for sustaining high electric fields. However, attaining all these desired qualities in a single dielectric material is a challenging task. An increase in the dielectric constant is often accompanied by an increase in the dielectric loss, leading to thermal management problems. On the other hand, an increase in the applied field stress can lead to early failure and low reliability of the capacitors.4) For maintaining the physical integrity, effective thermal management, and reliable operation of dielectric capacitors over a long time period, high electric fatigue endurance (> 106 cycles) and good thermal stability (−90°C to 250°C) of the dielectric material are essential (Fig. 1). Through a better understanding of the physical phenomena governing the properties of the dielectrics, efforts can be directed to realize an optimum combination of the aforementioned criteria.
To achieve high energy storage performances, various dielectric materials based on polymers, glasses, and ceramics have been studied. Polymer dielectrics exhibit high breakdown field (> 7 MV/cm), but low dielectric permittivity (< 10) and poor thermal stability (< 100°C). In order to improve their permittivity, recently, several polymer-based composites dispersed with dielectric ceramic fillers in different shapes and quantities have been developed.5) Glass-based oxide dielectrics possess greater permittivities and larger breakdown fields (> 10 MV/cm) compared to those of polymer dielectrics. Dielectric ceramics in bulk form exhibit permittivity in the range 10-2000 and their breakdown fields are of the order of 0.1-1 MV/cm. Depending on their dipolar/domain structures and electric-field-dependent changes in the polarization behavior, dielectric materials can be categorized into five major classes, namely, linear dielectrics (LD), paraelectrics (PE), ferroelectrics (FE), relaxor ferroelectrics (RFE), and antiferroelectrics (AFE) (Fig. 3). Each of these dielectric materials has its own advantages and limitations with regard to energy storage capability.
Although many review papers have been published on the dielectric capacitors based on polymers and their composites, reports dedicated to dielectric ceramics are rare.2,3,5,7-13) Recently, Yao et al.3) reviewed the energy storage performances of homogeneous/inhomogeneous-structured dielectrics of polymers, glasses, and ceramics. Chauhan et al.13) presented a review on anti-ferroelectric ceramics for energy storage capacitors. The present review covers most of the literature on dielectric ceramics and provides a comprehensive overview of the studies on the energy storage properties of the bulk ceramics belonging to LD, PE, FE, RFE, and AFE.

2. Dielectric Ceramics for Energy Storage Capacitors

2.1. Linear dielectrics

LD offer high BDS and linear polarization response to an applied electric field with minimal dielectric loss, which allows for large recoverable energy densities and efficiencies. Therefore, various LD ceramic compositions have been investigated for achieving high energy storage performance; some of the compositions are listed in Table 1. It is well known that the energy storage density of the linear dielectric is linearly proportional to the permittivity of the medium and the square of the maximum applied field. A larger BDS contributes more to achieving a high energy storage density. Since the BDS is mainly affected by the phase purity and microstructural features of the ceramics, many efforts have been made to improve it by using suitable dopants/oxide additives,14-18) low melting glasses,19) novel sintering technologies,20) utilizing the core-shell structures of initial particles,21) etc.
Shay et al.14) investigated the energy storage properties of pure and Mn-doped 0.8CaTiO3-0.2CaHfO3 (CHT) capacitors fabricated via tape casting. For the evaluation of the high electric field behavior of the CHT ceramics, single layers of CHT capacitors (thickness of 9 μm) consisting of Pt internal electrodes were fabricated. Pure CHT ceramics displayed a large energy density of 9 J/cm3 at 1200 kV/cm at room temperature (RT) owing to their high BDS and low hysteresis loss, however, a drastic reduction in the energy density was observed at elevated temperatures (Fig. 4(a)). Further, incorporation of Mn dopants into the CHT matrix significantly enhanced the BDS up to 1300 kV/cm and resulted in a much higher energy density of 9.6 J/cm3. Moreover, the temperature dependence of BDS and the ionic and electronic conductivities of the CHT ceramics were minimized (Fig. 4(b)).
In another study, Zhou et al.16) investigated the energy storage properties of Zr-doped CaTiO3 (CT) ceramics prepared by the conventional sintering method. With increasing concentration of Zr4+, the dielectric constant was found to decrease, while the BDS of the CT ceramics increased from 435 kV/cm to 756 kV/cm. As a result, the highest energy storage density of 2.7 J/cm3 was achieved for the CaZr0.4Ti0.6O3 system. The larger BDS achieved in the Zr-contained CT system is attributed to the decreased average field strength at the grain boundaries owing to its smaller grain size. Similarly, Mg-modified SrTiO3 (ST) ceramics exhibited finer grains with reduced grain activation energies, leading to much improved BDS (362 kV/cm) than pure ST ceramics (279 kV/cm); as a result, a larger Urec of 1.86 J/cm3 along with a higher efficiency (η) of 89.3% were achieved in the Sr0.99Mg0.01TiO3 system.18)
Since the BDS greatly depends on grain size, many researchers anticipated that grain size reduction is a feasible way to increase the DBS of a system. Zhao et al.19) produced fine-grained ST ceramics with an average grain size of 400 nm through the addition of SiO2, which led to an improvement in the BDS from 242 kV/cm to 361 kV/cm and resulted in a high Urec of 1.15 J/cm3. The addition of low temperature sintering aids such as ZnNb2O6 (ZN) and NiNb2O6 (NN) also decreased the grain size of ST-based ceramics, along with significant reductions in dielectric constant and dielectric loss. Moderate addition (6 wt.%) of ZN to Sr0.97Nd0.02TiO3 ceramics resulted in a high Urec of 2.37 J/cm3 at the applied electric field of 493 kV/cm.15) On the other hand, the addition of NN to Sr0.97La0.02TiO3 ceramics enhanced the BDS by boosting the grain boundary resistance, which led to an improved Urec of 1.36 J/cm3 (at 324 kV/cm).17)
Surface modifications of particles through high-resistance coatings were also employed to enhance the BDS of dielectric ceramics, where the coating acts as a shell and controls the grain growth occurring during sintering. Zeng et al.21) adopted the core-shell method to improve the BDS of ST ceramics by using SiO2 as a coating layer. The SiO2 layers with controlled thicknesses (2-13 nm) were coated on fine-grained ST particles by using Stöber process. The inter-diffusion occurring between the SiO2 shell and the ST cores during sintering facilitated grain growth suppression and secondary phase (Sr2TiSi2O8) formation, which resulted in enhanced BDS with reduced polarization. As the concentration of SiO2 increased, an enhancement in the BDS was observed up to 3 wt.% SiO2; above this concentration, BDS decreased due to abnormal grain growth. Optimized energy storage properties (Urec of 1.2 J/cm3 and η of 78.1% at 310 kV/cm) were realized for ST coated with 2.5 wt.% SiO2.
On the other hand, by taking advantage of doping with high permittivity (or high polarization) materials, it could be possible to enhance the energy storage properties of LD materials. In this fashion, Yang et al. obtained a high Urec of 2.59 J/cm3 along with an η of 85% even at the low electric field of 323 kV/cm in ST ceramics by doping with Bi0.48La0.02Na0.48Li0.02Ti0.98Zr0.02O3 (BLNLTZ).22) As shown in Fig. 4(c), the incorporation of BLNLTZ in ST ceramics significantly enhanced the saturation polarization from 7.95 μC/cm2 to 30.35 μC/cm2 by decreasing the BDS of the ST ceramics. In another study, substitution of BiScO3 into the crystal lattice of CaTiO3 resulted in improved dielectric and ferroelectric properties with enhanced BDS, which resulted in a higher Urec of 1.55 J/cm3 and η of 90.4% at 270 kV/cm, along with a power density of 1.79 MW/cm3 in 0.9CaTiO3-0.1BiScO3 ceramics.23) The enhanced energy storage properties were attributed to the enlarged bandgap caused by a strong hybridization between the O2p and Ti3d in the valence and conduction bands, as well as O2p and Sc3d hybridization in the conduction band.
Usually, enhancement in energy storage properties is achieved in LDs by compromising BDS or ɛr. It would be more beneficial if there is an improvement in both BDS and ɛr or an improvement in one property by maintaining the other property constant, though it is challenging. In this regard, few attempts have been made to improve the BDS as well as ɛr to realize high energy density properties. Zhou et al.20) produced fine-grained (~ 1 μm) high-density (99% of theoretical density) CaTiO3 (CT) ceramics by employing spark plasma sintering (SPS) technique. The SPS samples exhibited significantly improved dielectric properties (Fig. 4(d)) along with high BDS (Fig. 4(e)), resulting in a greatly enhanced Urec of 6.9 J/cm3 at the applied electric field of 910 kV/cm compared to that of conventionally sintered CT ceramics (Urec of 1.5 J/cm3 at 435 kV/cm). These remarkable properties of SPS-CT ceramics are attributed to the presence of discontinuous breakdown channels and microcrack networks, and the improved resistivity and thermal conductivity associated with small and uniform microstructures. In addition, with the introduction of amorphous alumina thin films in between the SPS-CT ceramic and the electrodes (SPS2), as shown in Fig. 4(f), a much improved BDS of 1188 kV/cm and Urec of 11.8 J/cm3 were obtained.

2.2. Paraelectric ceramics

In contrast to LD, nonlinear dielectrics such as PE ceramics having Curie temperatures below room temperature (RT) exhibit moderate ɛr and BDSs with low dielectric losses and weakly nonlinear P-E hysteresis that are promising for energy storage applications. Initially, Fletcher et al.24) demonstrated the feasibility of achieving the maximum energy storage density by using PE ceramic compositions (Sr-doped BaTiO3; BST) and realized energy storage of up to 8 J/cm3 at 1000 kV/cm. Afterwards, many efforts have been made to improve the energy storage performance of PE ceramics. Dong et al.25) investigated the energy storage properties of ZnO-doped Ba0.3Sr0.7TiO3 (BST + x wt.% ZnO (x = 0-5)) ceramics prepared by conventional sintering. The doping of ZnO to BST promoted densification and grain size reduction. As a result, improvements in the ɛr and BDS and a reduction in tanδ were observed at the optimal composition of BST + 1.6 wt.% ZnO, leading to a higher Urec of 3.9 J/cm3 at 400 kV/cm. In another study, enhancement in DBS and reduction in tanδ were observed at the expense of ɛr in BST ceramics doped with MgO nanopowder.26) The sample with the composition 0.7BST-0.3MgO exhibited the maximum Urec of 1.14 J/cm3 at 331 kV/cm.
Many studies have been conducted on the effect of grain size on the energy storage properties of BST-based ceramics as a result of the increasing requirement of miniaturization of electronic components.27-29) Song et al.27) prepared BST ceramics with different grain sizes (in the range 0.5-5.6 μm) by using the conventional sintering method and varying the sintering temperature. As the grain size decreased from 5.6 μm to 0.5 μm, ɛr decreased with the appearance of a diffuse-type transition (due to internal stress effect and polar nanoregions (PNRs)), whereas the BDS and maximum polarization were significantly enhanced. The improvement in the BDS is attributed to the enhanced grain boundary density. As a result, an improved Urec of 1.28 J/cm3 at 243 kV/cm was achieved in BST ceramics with an average grain size of 0.5 μm. In another study, BST ceramics of various grain sizes (0.405-1.635 μm) were synthesized by oxalate co-precipitation method and conventional and plasma-activated sintering (PAS) methods.28) Although the BST ceramics prepared through the PAS method exhibited small grains (0.405-0.550 μm) with a dense microstructure, the BDS (154-191 kV/cm) and Urec (0.63-0.94 J/cm3) values are very small owing to the smaller relative grain boundary resistance that resulted from residual oxygen vacancies (Rgb/(Rg+Rgb), where Rg and Rgb are the resistances of the grains and grain boundaries). On the other hand, the conventionally sintered samples displayed larger Rgb/(Rg+Rgb) values than the PAS samples, and showed an increasing trend with decreasing grain size, resulting in a larger Urec of 1.70 J/cm3 at 281 kV/cm that was obtained for the BST ceramic with grain size 0.66 μm.
Grain refinement had a great impact on the improvement of dielectric strength; however, it is difficult to achieve fine grains with uniform microstructures by using the conventional sintering route due to the uncontrolled grain growth that occurs during sintering. In this regard, various other sintering techniques such as microwave sintering (MWS)30) and SPS31,32) techniques have been employed to improve the energy storage properties of BST PE ceramics. Zhe et al.30) produced fine-grained (~ 0.65 ± 0.17 μm) BST ceramics with a dense and uniform microstructure by using the MWS method. The as-sintered MWS sample (at 990°C) exhibited high tanδ (> 0.1) and further thermal annealing in air at 1100°C for 10 h improved both the dielectric properties (ɛr ~ 910 and tanδ ~ 0.01) and the insulation properties. As a result, the thermally annealed MWS sample exhibited the maximum BDS of 180 kV/cm, compared to the conventionally sintered samples (130-154 kV/cm), which resulted in a larger Urec of 1.15 J/cm3 with an efficiency of 82%. In another study, Huang et al.31) investigated the SPS effect on the energy storage properties of BST ceramics. For this, ultrafine BST powders (45-105 nm) synthesized by sol-gel method and calcined at various temperatures (750-1050°C for 3 h) have been used. Further, the samples were sintered at 1000°C for 5 min. The rapid densification promoted by SPS allows direct grain boundary diffusion at higher temperatures by circumventing the surface diffusions that occur at low temperatures. As a result, highly dense microstructures (relative densities above 99%) with fine grains (173-238 nm) and few pores and cracks were obtained in the SPS sample. With increasing calcination temperature, enhancement in ɛr and BDS and reduction in tanδ were observed up to 950°C, which resulted in a maximum Urec of 1.23 J/cm3 at 240 kV/cm and efficiency of 94.5%; above this temperature, the properties slightly decreased. Usually, electrical breakdown in ceramics tends to occur at the weak links through the penetration of electrical currents at sufficiently high electric fields. However, electrical breakdown occurred in the SPS sample at relatively higher electric fields through the melting of grains rather than through the weak links. This significantly enhanced the BDS of the SPS sample containing fine grains with a pore-free microstructure, resulting in improved energy storage properties (Urec of 1.13 J/cm3 and η of 86.8%) compared to those of the conventionally sintered sample.32)
Since the sintering atmosphere also affects the microstructural and electrical properties of ceramic capacitors, some attempts have been made to investigate the effect of sintering atmosphere on the energy storage properties of BST-based paraelectric ceramics.33,34) Jin et al.33) synthesized BST powders by the hydrothermal method and subsequently sintered the ceramics in N2, air, and O2 atmospheres. The ceramics sintered in N2 and air atmospheres exhibited higher average grain sizes in the range 1.09-1.11 μm, whereas the sample sintered in O2 displayed an average grain size of 0.44 μm. The smaller grains with a homogenous microstructure in the O2-sintered sample could be attributed to the reduction in oxygen vacancies, which hindered grain growth as well as mass transport during sintering. Consequently, the O2-sintered sample displayed relaxor-like behavior with diffused-type transition (diffuseness coefficient = 1.618) and improved saturation polarization and BDS, which led to enhanced Urec of 1.08 J/cm3 and η of 73.8% at 167.5 kV/cm compared to the samples sintered in other atmospheres.
Gao et al.35) achieved high energy storage properties in Ba0.7Sr0.3TiO3-SrTiO3 (BST-ST) multilayer ceramics by taking advantage of the high polarization of BST ceramics and the high BDS of ST ceramics. A series of BST-ST multilayer ceramics have been fabricated by laminating various periodic combinations of the BST and ST layers. Introduction of the ST layer greatly decreased the dielectric loss and enhanced the BDS, however, a further increase in the number of ST layers drastically increased the leakage current due to the large accumulation of space charges and oxygen vacancies at the heterogeneous interfaces. At the optimal combination of B5S (i.e., a periodic combination of 5 BST layers and 1 ST layer), the multilayer ceramic exhibited a high BDS of 220 kV/cm and Urec of 2.3 J/cm3. Moreover, the BST-ST ceramics displayed good temperature- and frequency-stable dielectric properties.
In order to enhance the breakdown strength of the BST ceramics, the core-shell structure has been widely employed. Highly insulating oxides such as Al2O3 and SiO2 were used as coatings on PE particles.36-38) Huang et al. prepared core-shell structures of BST@SiO2 nanoparticles through the wet-chemical method and further sintered them by using the SPS technique.38) Upon increasing the SiO2 concentration of BST + x mol% SiO2 (i.e., x = 0, 5, 8, 12.5, 25, and 50), the average thickness of the SiO2 layer increased monotonously from 2.5 nm to 35 nm. The SPS sintered sample displayed a significant amount of the secondary phase (Ba,Sr)2TiSi2O8, and it’s intensity was enhanced with increasing SiO2 concentration. At lower concentrations (x ≤ 12.5) of SiO2, the BDS of the BST@SiO2 ceramics significantly improved up to 400 kV/cm at the expense of Pmax. However, excess amount of the SiO2 coating worsened both the BDS and Pmax of the BST@SiO2 ceramics. The BST ceramics containing 8 mol% SiO2 were the optimal combinations owing to their large Urec of 1.6 J/cm3 and η of 90.9%. In another study, BST nanoparticles coated with SiO2 and sintered using conventional sintering exhibited much improved energy storage properties such as a large Urec of 2 J/cm3 and an η of 80% even at the low electric field of 290 kV/cm.37) On the other hand, the BST ceramics fabricated from the nanoparticles coated with both Al2O3 and SiO2 layers could withstand a larger electric field of up to 493 kV/cm, as a result, an enormous energy storage density of 5.09 J/cm3 was achieved.36) Since glasses exhibit large BDS values, some attempts have been made to produce BST ceramics that can withstand higher electric fields by adding glasses. In this regard, Yang et al.39) studied the effect of glass (Bi2O3-B2O3-SiO2; BBS) addition on the energy storage properties of BST ceramics. The addition of glass to BST ceramics decreased the sintering temperature effectively and improved the frequency stability, BDS, and Pmax. The BST ceramics containing 9 wt% BBS exhibited excellent energy storage properties of Urec 1.98 J/cm3 and η 90.57% at 279 kV/cm.
With respect to the other family of BST ceramics, Zhang et al.40) attempted to study the energy storage properties of Ca-doped ST ceramics. The incorporation of Ca ions at the Sr-sites of the ST ceramics led to improvements in ɛr and BDS, while a reduction in tan δ was observed. At the applied electric field of 333 kV/cm, the Sr0.98Ca0.02TiO3 sample revealed a Urec of 1.95 J/cm3, with η being 72.3%, which is 2.8 times larger than that of pure ST ceramics.
Since the materials with a PE phase at RT display outstanding energy storage properties, many researchers explored the idea of shifting the Curie temperature (TC) of ferroelectrics through intentional doping. Zhou et al.41) succeeded in reducing the TC of the (Ba0.85Ca0.15)(Zr0.10Ti0.90)O3 (BCZT) ceramics to below RT by doping with a B-site (Ni1/3Nb2/3)4+ (NN) complex ion. The BCZT-NN ceramics showed a single-phase perovskite structure and good frequency and temperature stability. Furthermore, doping with NN reduced the P-E hysteresis loss and enhanced the BDS of BCZT ceramics. The maximum Urec of 0.66 J/cm3 with an η of 88.1% at 200 kV/cm was achieved in the case of BCZT-0.3NN. In another study, YNbO4 (YN) dopant was used to tailor the dielectric and ferroelectric properties of BT ceramics.42) With increasing YN concentration, the TC of (1-x)BT-xYN (x = 0-15%) ceramics was shifted from 130°C to below RT, along with a significant suppression in the dielectric nonlinearity and the P-E loops becoming slimmer with lower Pr and enhanced BDS values; as a result, a maximum Urec of 0.614 J/cm3 with an η of 86.8% at 173 kV/cm was obtained for 0.93BT-0.07YN, which was 2.4 times larger than that of the pure BT ceramic.

2.3. Ferroelectric ceramics

FE ceramics exhibiting nonlinear electric field dependent polarization characteristics with high saturation polarizations (high permittivities) are of particular interest in achieving superior energy storage properties under smaller electric fields. However, the high dielectric loss and fat P-E hysteresis loops resulting from domain switching enforce the low BDS as well as smaller energy storage density of FE ceramics. Among the various FE ceramics, a few efforts have been made to improve the energy storage properties of (Bi, Na)TiO3 (BNT),43-45) Ba(Zr, Ti)O3 (BZT),46-48) BaTiO3 (BT),49-52) and (K, Na)NbO3 (KNN)53) based ceramics. Gao et al.43) studied the effect of tetragonality ratio (c/a ratio) on the energy storage properties of (0.9-x) Bi0.5Na0.5TiO3-xBa-TiO3-0.1K0.5Na0.5NbO3 (x = 0.060-0.069) [BNT-BT-KNN] ceramics by varying the BNT/BT ratio. As the BNT/BT ratio increased, the c/a ratio also increased initially (up to x = 0.063), and then decreased. The sample having a larger c/a ratio (~ 0.709) exhibited the maximum value of Ps-Pr, which led to an enhanced Urec of 0.424 J/cm3 at 50 kV/cm. The c/a ratio dependence of the Urec of BNT-BT-KNN ceramics is depicted in Fig. 5(a), which reveals an almost linear relation. In another study, highly dense BCT and BZT ceramics prepared by conventional sintering exhibited larger c/a ratios of 1.027 and 1.002, as a result, much improved energy densities of 1.41 J/cm3 (η of 61%) and 0.71 J/cm3 (η of 19%) at 150 kV/cm, respectively, were realized.47) On the contrary, in spite of the decrease in the c/a ratio from 1.010 to 1.003, NaNbO3 (NN) modified 0.92BaTiO3-0.08K0.5Bi0.5TiO3 (BTKBT) ceramics displayed much improved energy storage properties (Urec of 1.96 J/cm3 and η of 67.4% at the electric field of 220 kV/cm) due to the reduction in grain size that was facilitated by the defect dipoles ( VNa-VO¨-VNa) induced during sintering.52)
Sreenivas et al.46) investigated the energy storage properties of (1-x) BZT-x BCT (x = 0.10-0.30) based ceramic capacitors sintered at 1600°C. For all compositions, the ceramics exhibited a single-phase perovskite structure without any secondary phases and the average grain sizes were in the range 20-30 μm. The ceramic corresponding to x = 0.15 displayed a relatively higher ɛr (8400) with low tan δ and large BDS of 170 kV/cm, leading to an enhanced Urec of 0.68 J/cm3 with an η of 72%.
Microstructural modification of FE nanoparticles was also adopted for improving the energy storage properties of FE ceramics. Ma et al.50) utilized the double coating technique to prepare multilevel core-shell structures of BT@La2O3@SiO2 particles. The combined effects of structural distortion, which led to an improvement in the dielectric property due to La2O3 and the acceleration of sintering, as well as density promotion by SiO2, led to enhanced energy storage properties (Urec of 0.54 J/cm3 and η of 85.7% at 136 kV/cm) in BT@La2O3@SiO2 ceramics containing 9 wt% SiO2. However, excess amounts of SiO2 (> 9 wt%) promoted the interface reaction and the formation of the Ba2TiSi2O8 secondary phase, which lead to the collapse of the energy storage properties.
It is well known that fine grains with pore-free structures are favorable for improving the BDS and energy density properties of ceramics. Since the microstructural features of ceramics are affected by the fabrication method, many researchers have attempted to tailor the energy storage properties of the FE ceramics fabricated by various methods.45,51) Xu et al.45) investigated the energy storage properties of (1-x) 0.93BNT-0.07BT-x KNbO3 (x = 0-0.07) (BNTBT-KN) ceramics synthesized via wet-chemical method and sintered using the conventional method. Initially, the BNT-BT and KN powders were synthesized by sol-gel and hydrothermal methods to obtain fine powders and the stoichiometric mixtures were sintered at 1050-1175°C for 2 h. The ceramic with x = 0.05 (5KN) exhibited the maximum Urec of 1.72 J/cm3 owing to its higher BDS (168 kV/cm), increased ɛr (1550), and reduced grain size (1.03 μm) compared to those of pure BNTBT ceramics. Moreover, the wet-chemical synthesized 5KN ceramics displayed an almost 90% enhanced BDS and 74% enhanced recoverable energy density compared with the 5KN ceramics prepared via the solid-state method (Urec of 0.99 J/cm3 at 88.5 kV/cm). In another study, Ma et al.51) demonstrated the feasibility of achieving fine-grained highly dense BT ceramics even at sufficiently low temperatures by employing the cold sintering method. The pellets were prepared from hydrothermal precursors of BT nanoparticles and cold sintered at 180°C for different dwelling times (15-120 min). Subsequently, all sintered samples were dried and annealed in air at 900°C for 3 h to induce densification. Among all the samples, that sintered for 60 min exhibited a relatively high density (96.8%) and improved dielectric properties (ɛr of 2332 and tan δ of 0.01 at 1 kHz). The fine grains associated with the high density resulted in an improved energy density of 1.45 J/cm3 with an η of 85.6% at the applied electric field of 90 kV/cm.
By utilizing the potential of sintering aids to reduce the sintering temperature, Qu et al.53) produced highly dense fine-grained 0.9(K0.5Na0.5)NbO3-0.1Bi(Mg2/3Nb1/3)O3 (KNN-BMN) ceramics through liquid phase sintering. The sintering temperatures of the KNN-BMN ceramics were effectively decreased from 1150°C to 930°C with the addition of CuO, as shown in Fig. 5(b). Moreover, CuO-modified KNN-BMN (KNN-BMN-1.0 mol% CuO) ceramics could withstand high electric fields of up to 400 kV/cm owing to their dense microstructure without any porosity and displayed a large polarization difference (Ps-Pr) due to the strong hybridization between Bi6p and O2p, leading to exceptional energy storage properties (Urec of 4.02 J/cm3 and η of 57.3%) (Fig. 5(c-d)).

2.4. Relaxor ferroelectric ceramics

RFE ceramics are drawing much attention for energy storage applications owing to their outstanding dielectric and FE properties. Similar to the FE, RFE materials also exhibit large permittivities and saturation polarizations, but possess lower remnant polarizations and slimmer hysteresis loops, which are essential for realizing extremely high energy densities and efficiencies. These materials are mainly characterized by the broad frequency-dependent peak of the temperature-dependent dielectric susceptibility and the slim P-E hysteresis loops. The RFE behavior is assumed to originate from the PNR, which usually appears below Burn’s temperature.

2.4.1. Lead-based RFE ceramics

Quite a few lead-based relaxor ceramics such as PbZrO3-(SrTiO3),54) Pb(Mn1/3Nb2/3)O3-PbTiO3,55-57) and La-doped Pb(Zr, Ti)O358-60) were examined for energy storage applications by considering the human health and environmental concerns and their thermal stabilities. Recently, Zhang et al.54) investigated the energy storage performance of (1-x) PbZrO3-x SrTiO3 (PZ-ST) (x = 10-30 mol%) ceramics prepared by the solid state reaction method. The incorporation of ST in the PZ matrix induced relaxor behavior by transforming the macrodomains of PZ into microdomains, which resulted in slim hysteresis loops with enhanced saturation polarizations. As a result, a maximum Urec of 0.46 J/cm3 with an η of 79.3% at the applied electric field of 79.3 kV/cm was achieved in 0.7PZ-0.3ST relaxor ceramics. Moreover, 0.7PZ-0.3ST ceramics displayed oxygen-vacancy (Vö)-induced high-temperature dielectric relaxation. In another study, Zhang et al.57) reported relaxor behavior in Pb(Mn1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics that was induced by the formation of complex defect dipoles Vö-Nb4+. Li et al.58) investigated the effect of excess amount of lead (PbO) on the energy storage properties of (Pb0.97(1+x)La0.02)(Zr0.95Ti0.05)O3 (PLZT2/95/5) (x = 0-15%) ceramics. As the concentration of PbO increased, the Urec of the PLZT2/95/5 ceramics increased from 0.36 J/cm3 to 1.94 J/cm3 at the electric field of 90 kV/cm due to the increased dielectric relaxation resulting from the volatilization of PbO during sintering. Further, Urec also showed temperature dependence and reached a maximum value of 2.12 J/cm3 (η of 92.98%) at 120°C due to the AFE to RFE phase transition in the PLZT2/95/5 ceramics containing more than 10% PbO. Besides, Gao et al.59) reported that the (Pb0.9La0.1)(Zr0.65Ti0.35)O3 (PLZT10/65/35) ceramics displayed good temperature stability with a slight variation in Urec (< 15%) over the temperature range 24-83°C, when measured at 25 kV/cm. This temperature stability results from the continuous formation and growth of PNRs with temperature, as well as the applied electric field. In addition, the other PLZT ceramics ((Pb0.88La0.08)(Zr0.91Ti0.09)O3; PLZT8/91/9) also exhibited good fatigue lives of up to 105 electric field cycles without any significant degradation.60) Moreover, the PLZT8/91/9 ceramics were able to withstand large electric fields of up to 170 kV/cm, leading to the realization of a superior Urec of 3.04 J/cm3 and an η of 92%.

2.4.2. Lead-free RFE ceramics

(a) BaTiO3-based RFE ceramics

BaTiO3-based RFE ceramics and solid solutions are considered as one of the most promising candidates for energy storage applications. Ogihara et al.61) demonstrated the high-temperature stable energy storage properties of 0.7Ba-TiO3-0.3BiScO3 (BTBS) ceramics prepared via the tape casting method. From Fig. 6(a), the appearance of diffusive and dispersion phase transitions is indicative of the relaxor behavior of BTBS ceramics, which is also evidenced from the slim P-E loops (Fig. 6(b)). Further, the BDS was found to increase with decreasing thickness of the capacitor, and relatively high BDS (730 kV/cm) and Urec (6.1 J/cm3) were obtained for a 15 μm thick BTBS single layer capacitor. Moreover, the BTBS capacitors exhibited good thermal stability over a wide temperature range 0-300°C (Fig. 6(c)), and the obtained results are superior to those of the commercially available capacitors. Since then, many researchers have investigated the energy storage performance of various BT-based RFE solid solutions such as BaTiO3-Bi(Mg2/3Nb1/3)O3,62,63) BaTiO3-Bi(Mg1/2Nb1/2)O3,64,65) BaTiO3-Bi(Zn2/3Nb1/3)O3,66) and BaTiO3-Bi0.5Na0.5TiO3-Na0.73Bi0.09NbO3.67) Wang et al.62) reported that the addition of Bi(Mg2/3Nb1/3)O3 (BMN) to BT ceramics induced relaxor behavior that was attributed to the large difference in ionic radii of B-site cations and A-site cations. With increasing concentration of BMN, the diffused phase transition became flat and exhibited good temperature stability (ɛr ~ 628-787) over a wide temperature range (−50-300°C). Moreover, the decrease in ɛr and increase in resistivity with BMN concentration leads to an improvement in the BDS of BT-BMN ceramics, which helps to enhance the Urec. The highest Urec of 1.13 J/cm3 with an η of 96% at the applied electric field of 143.5 kV/cm was achieved for 0.9BT-0.1BMN. Li et al.63) prepared MnCO3-doped 0.9BT-0.1BMN ceramics to improve the energy storage properties by mitigating the dielectric as well as ferroelectric losses. As reported, acceptor (Mn2+) doping-induced dipoles ( Mn2+-Vo) can generate an internal electric field, which can act as a restoring force to return the domain to its original state after removing the external field. Therefore, the Pmax-Pr and BDS improved significantly with an increase in MnCO3 concentration, while ɛr and tan δ slightly decreased. However, further increasing the MnCO3 concentration resulted in both Pmax-Pr and BDS of 0.9BT-0.1BMN being reduced. The optimum energy storage properties were achieved in 0.9BT-0.1BMN-3 wt% MnCO3 ceramics with Urec of 1.7 J/cm3 and η of 88.6% at the applied electric field of 210 kV/cm. Solid solution modification of BT with Bi(Mg1/2Ti1/2)O3 (BMT) has led to a dispersive and temperature-independent ɛr behavior over the temperature range −50-300°C.64,68) The maximum Urec of 1.81 J/cm3 with an efficiency of 88% at the electric field of 287 kV/cm was obtained in 0.88BT-0.12BMT ceramics.64) In another study, the addition of B2O3-SiO2 glass to 0.88BT-0.12BMT ceramics further enhanced the BDS as well as thermal stability and improved the energy density from 1.64 J/cm3 to 1.97 J/cm3, with η being above 94%.65) In a separate study, the addition of Bi(Zn2/3Nb1/3)O3 (BZN) enhanced the insulation ability of BT ceramics by increasing the activation energies of both the grains and grain boundaries.66) Moreover, a significant reduction in dielectric nonlinearity and linear-like P-E loops with negligible hysteresis loss were noticed at higher concentrations of BZN. Among the ceramics of various compositions, a maximum Urec of 0.79 J/cm3 with η 93.5% at 131 kV/cm was realized in the case of 0.85BT-0.15BZN. Yang et al.67) considered the doping of Na0.73Bi0.09NbO3 (NBN) to be a good choice to improve the Pmax-Pr and BDS of 0.65BaTiO3-0.35Bi0.5Na0.5TiO3 (0.65BT-0.35BNT) ceramics. With increasing NBN content, the degree of relaxor behavior increased despite the increase in grain size from 0.21 μm to 0.56 μm. Meanwhile, the dielectric as well as energy storage properties of (1-x) 0.65BT-0.35BNT- xNBN (x = 0-0.14) ceramics initially improved and then decreased. A high Urec of 1.70 J/cm3 with η 82% at 172 kV/cm was achieved in 0.92(0.65BT-0.35BNT)-0.08NBN ceramic. Wu et al.69) adopted the microstructural modification of BT particles with BiScO3 (BS) coating by employing the core-shell method to tailor the energy storage properties. With the BS coating, grain size suppression, BDS improvement, conductivity reduction, and broadened peaks with sequential disappearance of structural transitions were observed. Moreover, the local compositionally graded structures arose from the diffusion of Bi and Sc into the BT matrix that resulted in temperature-independent dielectric properties. All these factors improved the energy storage properties (Urec of 0.68 J/cm3 and η of 81% at 120 kV/cm) of 3 mol% BS-coated BT ceramics.

(b) (Na, Bi)TiO3-based RFE ceramics

Among the lead-free ceramics, (Na, Bi)TiO3 (NBT)-based FE ceramics were extensively studied owing to their excellent ferroelectric properties that can be ascribed to the (Na, Bi)2+ ions, especially the lone-pair 6s2 electronic configuration of Bi3+.71) At RT, NBT exhibits a rhombohedral FE structure that transforms to a weakly polar tetragonal phase at elevated temperatures, which is either a RFE or an AFE phase. Therefore, many efforts have been made to induce relaxor behavior and improve the BDS of the NBT ceramics by doping and forming binary/ternary solutions.
Recently, Liu et al.72) reported the energy storage properties of BNT-based binary solutions such as Ba0.06Na0.47Bi0.47TiO3-Ln1/3NbO3 (BNBT-LnN, Ln = La, Nd, Sm) ceramics. The introduction of LnN in BNBT ceramics significantly reduced the polarizations (Pr and Pmax) and promoted the relaxor behavior, which lead to a maximum Urec of 1.239 J/cm3 at 100 kV/cm in the case of 0.98BBNT-0.02SmN. The deliberate doping of Sr0.85Bi0.1TiO3 (SBT) in NBT ceramics induced ergodic relaxor behavior with reduced Pr and improved Pmax, as a result, a larger Urec of 1.5 J/cm3 and an η of 73% were achieved under a relatively lower electric field (85 kV/cm).73) In addition, the BDS and ionic conductivity of the BBNT ceramics were enhanced, whereas the Pr, Pmax, and electronic conductivity reduced with SrZrO3 (SZ) doping.74)
Pu et al.75) investigated the effect of Sn4+ doping on the energy storage properties of 0.55Bi0.5Na0.5TiO3-0.45Ba0.85-Ca0.15Ti0.9Zr0.1O3 (0.55BNT-0.45BCTZ) ceramics. With the increase in Sn4+ concentration, a diffuse-type phase transition with broad plateau-like dielectric constant maxima over a wide temperature range was observed. In addition, the low ionic polarizability of Sn4+ facilitated the softening of the current peaks and the reduction of hysteresis loss. As a consequence, improved energy storage properties (Urec of 1.21 J/cm3 and η of 72.29% at 130 kV/cm) were realized in 0.55Bi0.5Na0.5TiO3-0.45Ba0.85Ca0.15Ti0.85Zr0.1Sn0.05O3 (0.55BNT-0.45BCTZS) ceramics. In an extension of this study, the energy storage properties of BNT-BCTZ were further enhanced by doping with MgO and utilizing microwave sintering.76,77)
Since reduction in leakage current is an effective way to enhance the BDS of ceramics, Yang et al.70) considered La3+ doping for minimizing the remnant polarization and leakage current of BNT-based ceramics. With increasing La3+ concentration in Bi(0.5-x)Lax(Na0.82K0.18)0.5Ti0.96Zr0.02Sn0.02O3 (BNKTZS-xL) (x = 0-0.18) ceramics, a gradual decrease in grain size, as well as structural transition with enhanced relaxor behavior, was noticed. Moreover, BNKTZS-xL (x = 0.06-0.18) samples exhibited good temperature stability with improved temperature coefficient of capacitance (≤ ± 15% at 150°C). The polarization (Pr and Pmax) properties and leakage current density (Fig. 6(d)) of BNKTZS-xL ceramics decreased continuously with increasing x, as a result, the hysteresis loss decreased, while the BDS was enhanced from 80 kV/cm to 155 kV/cm. A maximum Urec of 1.95 J/cm3 with an η of 71% was obtained for BNKTZS-0.1L. In another study, the introduction of BaSnO3 (BSN) into NBT ceramics also suppressed the phase transition temperature as well as the leakage current peaks and increase the ability of the ceramics to withstand higher electric fields, which in turn resulted in the BDS increasing from 140 kV/cm to 240 kV/cm and yielded a maximum Urec of 1.91 J/cm3 and η of 86.4% for 0.75NBT-0.25BSN.78)
On the other hand, BNT-based ternary systems based on the solid solutions of various ABO3-type ferro/non-ferroelectrics at the morphotrophic phase boundary (MPB) were also extensively studied to expand the thermal stability range as well as to increase the energy storage capacity by shifting the transition temperature (especially Tm) towards RT.79) Among the BNT-based ternary systems, (Bi0.5Na0.5)TiO3-(Bi0.5K0.5)TiO3-(K0.5Na0.5)NbO3,80) Bi0.5Na0.5TiO3-BaTiO3-Na0.73Bi0.09NbO3,81) BiTi0.5Zn0.5O3-Bi0.5Na0.5TiO3-BaTiO3,82) Bi0.5Na0.5TiO3-NaNbO3-Ba(Zr0.2Ti0.8)O3,83) Bi0.5Na0.5TiO3-BaTiO3-NaTaO3,84) Na0.5Bi0.5TiO3-BaTiO3-NaNbO3,85) and Bi0.48La0.02Na0.48Li0.02Ti0.98Zr0.02O3-Na0.73Bi0.09NbO386) exhibited excellent energy storage properties (> 1 J/cm3) with good temperature stability and fatigue-free behavior.

(c) (K0.5Na0.5)NbO3 (KNN)-based RFE ceramics

A Few studies have been dedicated to improving the DBS of KNN-based ceramics through compositionally controlled grain size and porosity reduction.87-91) Qu et al. achieved a high energy storage density in Sr(Sc0.5Nb0.5)O3 (SSN)-doped fine-grained KNN ceramics ((1-x)KNN-xSSN, x = 0-0.3) prepared by conventional sintering.87) The crystal structure of the KNN ceramics gradually transformed from orthorhombic symmetry to cubic symmetry, accompanied by a decrease in grain size from 4 μm to 0.4 μm, and a strong frequency dispersion of ɛr with diffuse phase transitions were observed with increasing concentration of SSN. Moreover, the small grain size together with reduced porosity favored good transparency in the visible region as well as enhanced DBS up to 295 kV/cm, as a result, a larger Urec of 2.02 J/cm3 with an η of 81.4% were realized in 0.8KNN-0.2SSN ceramics. The addition of a sintering aid such as ZnO further enhanced the DBS from 295 kV/cm to 400 kV/cm, resulting in an improved Urec of 2.6 J/cm3 and an η of 73.2% for 0.8KNN-0.2SSN ceramics containing 0.5 mol% ZnO.89) Inspired by these results, different dopants such as ST,88) Sr(Zn1/3Nb2/3)O3 (SZN),90) Bi2O3,92) and Bi(Mg2/3Nb1/3)O3 (BMN)91) were used to reduce the average grain size and improve the BDS of KNN ceramics and obtain the maximum Urec (η) values of 4.03 J/cm3 (52%) at 400 kV/cm, 1.5 J/cm3 (50%) at 175 kV/cm, 1.04 J/cm3 at 189 kV/cm, and 4.08 J/cm3 (62.7%) at 300 kV/cm.

(d) Other lead-free RFE ceramics

This section provides an overview of the energy storage performances of various solid solutions of BiFeO393-95) and ST96-103) based lead-free RFE ceramics. A few attempts have been made to study the doping effect of low dielectric loss materials such as Ba(Mg1/3Nb2/3)O3 (BMN)93) and La(Mg1/2Ti1/2)O3 (LMT)94) on the energy storage performance of 0.67BiFeO3-0.33BaTiO3 (0.67BF-0.33BT) ceramics. The doping of these materials favored the decrease in the size of PNRs and enhanced their dynamics, consequently, a steady decrease in Pr and shifting of temperature (Tm) corresponding to the ɛr maxima towards RT with the increase in dielectric relaxation behavior (i.e., increased values of γ and ΔTrelax = Tm@1kHz - Tm@1MHz with increasing dopant concentration) and temperature stability were observed. Moreover, the coexistence of ergodic and non-ergodic behaviors at RT in optimal compositions lead to improved energy storage properties (Urec = 1.56-1.66 J/cm3 and η = 75-82%) even under small electric fields (125-130 kV/cm). In another study, the doping of the less polarizable Nd in Bi-sites stabilized the pseudocubic phase of BF-BT ceramics, with decreases in Tm and ferroelectricity.95) At the optimal composition of 0.75(Bi0.85Nd0.15)FeO3-0.25BaTiO3 + 0.1 wt.% MnO2 (BN15F-BT), a maximum Urec of 1.82 J/cm3 with an η of 41.3% at 170 kV/cm was achieved. By utilizing the advantage of interfacial modification in improving the BDS of BN15F-BT ceramics, the authors fabricated a multilayer capacitor (of thickness 0.78 mm) by using an optimized composition of BN15F-BT and Pt internal electrodes, which helped the ceramics withstand electric fields of up to 540 kV/cm and yielded a much improved Urec of 6.74 J/cm3 and η of 77%. Moreover, the multilayered BN15F-BT capacitor exhibited fast discharging (τ0.9 ~ 4 μs, the time required to release 90% of its total stored energy) and good thermal stability (ΔUrec ~ 15%) in the temperature range 30-125°C.95)
It is well known that ST possesses high BDS and η, but low Pmax. In order to achieve a high Urec along with high η, many researchers adopted compositional modification to improve the Pmax (or ɛr) of ST-based ceramics.96-103) For example, the incorporation of (Na0.5Bi0.5)2+ and Ba2+ in the A-sites of ST ceramics increased the lattice disorder as well as the growth of PNRs, which in turn enhanced the relaxor behavior along with improved polarization properties.98,99,102,103) Further, the addition of ZrO2 improved the BDS by stabilizing the pseudocubic phase and charge on Ti and suppressing the dissociation of oxygen during the sintering of 0.6ST-0.4NBT ceramics.100) As the ZrO2 concentration increased from 0.1 mol% to 0.5 mol%, the BDS increased from 220 kV/cm to 285 kV/cm, as a result, a maximum Urec of 2.84 J/cm3 with an η of 71.54% has been achieved. Similarly, Sn4+ doping also effectively reduced the average grain size and dielectric loss and improved the BDS as well as the energy storage properties of 0.45ST-0.2NBT-0.35BT ceramics.103)
Yan et al.96) reported that doping of 0.95Bi0.5Na0.5TiO3-0.05BaAl0.5Nb0.5O3 (NBT-BAN) significantly enhanced the Pmax (from 4.70 μC/cm2 to 41.81 μC/cm2), with a slight increase in Pr, which was accompanied by a 10.39 times improvement in the dielectric constant of the ST ceramics; this led to the realization of a high Urec of 1.89 J/cm3 with η being 77% at 190 kV/cm for the 0.5ST-0.5(NBT-BAN) system. Yang et al.101) reported an improvement in the energy storage properties (Urec of 2.83 J/cm3 and η of 85% at 320 kV/cm) of 0.93Bi0.5Na0.5TiO3-0.07Ba0.94La0.04Zr0.02Ti0.98O3 (NBT-BLZT)-doped ST ceramics due to the improvement in Pr-Pmax and grain size.

2.5. Antiferroelectric ceramics

The absence of FE dipoles at smaller electric fields and the field-induced reversible FE phase at higher fields lead to low remnant and high saturation polarizations in AFE materials, which make them promising for energy storage applications.13,104) Among the various AFE materials, PbZrO3 (PZ), (Na, Bi)TiO3 (NBT), and AgNbO3 (AN) based ceramics have been widely investigated for their suitability for energy storage applications. Since a large switching electric field (EAFE-FE) and slim hysteresis (i.e., small ΔE = EAFE-FE-EFE-AFE) along with large polarization are required to obtain high energy storage densities in AFE ceramics, various approaches such as chemical modification, different fabrication methods, and mechanical confinement have been adopted.

2.5.1. Lead-based AFE ceramics

Sawaguchi et al. demonstrated that AFE behavior in PZ originated from the antiparallel displacement of Pb2+ in the plane perpendicular to the c-axis.105) For the stabilization of the AFE phase in PZ ceramics, various dopants such as Ba, La, Sr, Sm, or Y in the Pb-sites and Nb, Sn, or Ti in the Zr-sites have been used. Among the various lead-based materials, (Pb, La)(Zr, Ti)O3 (PLZT),106,107) (Pb, La)(Zr, Sn, Ti)O3 (PLZST),108-120) Pb(Nb, Zr, Sn, Ti)O3 (PNZST),121,122) (Pb, La) (Nb, Zr, Sn, Ti)O3 (PLNZST),123) (Pb, La, Ba)(Zr, Sn, Ti)O3 (PLBZST),124-130) (Pb, La, Ba, Y)(Zr, Sn, Ti)O3 (PLBYZST),131-134) (Pb, Sm)(Zr, Sn, Ti)O3 (PSZST),135) and Pb(Tm, Nb)O3-Pb(Mg, Nb)O3 (PTN-PMN)136) based AFE ceramics have been considered as promising candidates for energy harvesting applications.
After the establishment of the triaxial phase diagram of the La3+-doped Pb(Zr, Sn, Ti)O3 system,137) the PLZST-based AFE system has been extensively investigated for energy storage applications.108-120) At RT, the PLZST AFE ceramics exist in either the tetragonal (AFET) phase or the orthorhombic (AFEO) phase, depending on the composition; the ceramics with the AFEO phase display relatively higher EAFE-FE than those with the AFET phase. In this regard, some efforts have been made to improve the stability of the AFEO phase of the PLZST ceramics via compositional modification.112,114,116,118,120) For example, Wang et al.112) tailored the Zr/Sn and Zr/Ti ratios of PLZST ceramics and realized improved energy storage properties for Zr-rich compositions due to the increase in AFEO phase stability. A higher EAFE-FE (227 kV/cm) along with a square-type hysteresis loop (ΔE ~ 90 kV/cm) and maximum polarization (30 μC/cm2) were achieved for Zr/Sn = 90/05. Although larger EAFE-FE (275 kV/cm) and slanted hysteresis (ΔE ~ 28 kV/cm) loops were realized in Zr/Ti = 92/03 composition, Pmax was quite low. The composition of Pb0.97La0.02(Zr0.90Sn0.05Ti0.05)O3 was optimal owing to its high Urec of 4.426 J/cm3 at 300 kV/cm with an η of 61.2%. In another study, Zhang et al.118) reported that the substitution of Zr4+ for Sn4+ transformed the crystal structure of PLZST ceramics from AFET to AFEO and shifted the AFE-FE and FE-AFE transitions towards higher electric fields, which led to an improvement in Urec from 3.18 J/cm3 to 4.38 J/cm3. In a recent study, Liu et al.120) studied the effect of different concentrations of Zr and Ti on the phase transition behavior and energy storage performance of tetragonal structured Pb0.97La0.02(ZrxSn0.925-xTi0.075)O3 (x = 0.58-0.82) and Pb0.97La0.02(Zr0.58Sn0.42-yTiy)O3 (y = 0.07-0.11) systems. Both systems exhibited small EAFE-FE and EFE-AFE, with large DE values at the MPB compositions. As the Zr concentration increased (at a fixed Ti concentration), both EAFE-FE and EFE-AFE linearly decreased, while DE increased; as a result, Urec as well as η were reduced. On the other hand, decreasing the Ti concentration (at a fixed Zr concentration) resulted in improved energy storage properties (Urec ~ 2.35 J/cm3 and η ~ 86% for y = 0.07) due to increases in both EAFE-FE and EFE-AFE. A few attempts have been made to replace Pb2+ (1.49 Å) with smaller ionic radii elements (Sr and Sm) to reduce the tolerance factor, which can help to improve the stability of the AFE phase of PLZST ceramics.116,117,135) Zhang et al.116) reported that with the incorporation of the inert-gas-type outermost electron configuration (4s24p6) of Sr2+ in Pb2+ (6s2, non-inert type), the crystal structure of (Pb0.97-xSrxLa0.02)(Zr0.75Sn0.195Ti0.055)O3 (x = 0-0.025) changed from AFET to AFEO, ɛrm and Pmax decreased, and the Tm and switching fields (EAFE-FE and EFE-AFE) increased. As a result, the Urec increased with increasing Sr2+ concentration and reached a maximum of 5.56 J/cm3, with the η being 67.9% at 350 kV/cm for x = 0.015. In addition, the PLZST-based ceramics exhibited good temperature stability and released their stored energy in less than 200 ns.115-117)
A few studies have attempted to investigate the effect of Ba doping on the energy storage properties of PLZST ceramics.124,128) The doping of Ba2+ in Pb2+ sites led to enhanced energy storage properties due to the improvements in ɛr and Pmax, however, significant decreases in the switching fields and phase transition temperatures were noticed. On the other hand, the incorporation of the smaller ion Y3+ to substitute Pb2+ lead to decreases in oxygen vacancies and the grain size of (Pb0.87Ba0.1La0.02) (Zr0.65Sn0.3Ti0.05)O3 + x mol% Y (PBLZST-xY, x = 0-1.25) ceramics, which facilitated an increase in the internal stress between the grains; therefore, higher switching fields and smaller ΔE were observed.131) For low concentrations (up to 0.75 mol%) of Y, the Urec of the PBLZST ceramics increased from 2.20 J/cm3 to 2.75 J/cm3, however, at higher concentrations, it decreased due to the reduction in Pmax. Since the electrical properties of Pb-based AFE ceramics are mainly affected by the density and lead loss during sintering, Zhang et al.127) adopted the hot-press (HP) method and added excess PbO to improve the electrical properties of PBLZST + 0.75 mol% Y ceramics. The HP samples exhibited improved microstructures, with relative densities of more than 98%, and enhanced resistivity compared to the samples obtained by the conventional sintering method. Moreover, hot-pressed PBLZST + 0.75 mol% Y with an appropriately excess amount of PbO (6 mol%) displayed a much higher BDS and Pmax, leading to a high Urec of 3.2 J/cm3 (at 180 kV/cm), which is almost twice that of the CS sample (1.6 J/cm3).
The AFET ceramics can possess larger Pmax but smaller switching fields compared to those of the AFEO ceramics; by utilizing the large switching field (or large BDS) of the AFEO ceramics, it could be possible to obtain improved Urec in AFET and AFEO two-phase composite ceramics. In this context, Zhang et al.132) investigated the energy storage properties of (Pb0.858Ba0.1La0.02Y0.008)(Zr0.65Sn0.3Ti0.05)O3-x(Pb0.97La0.02) (Zr0.9Sn0.05Ti0.05)O3 (PLBYZST-PLZST, x = 0-100 wt%) AFE composite ceramics. As the PLZST concentration was increased from 0 to 50 wt%, EAFE-FE increased from 80 kV/cm to 130 kV/cm without a significant decrease in Pmax, resulting in an improved Urec of 4.65 J/cm3 with an η of 60% at 200 kV/cm. Moreover, the dielectric temperature stability was enhanced through the shifting of both the dielectric peaks (AFEO-AFET and AFET-PE) towards higher temperatures. However, both EAFE-FE and Pmax decreased when the PLZST concentration exceeded 50 wt%, due to enhanced compositional heterogeneity and the appearance of a secondary phase. In order to suppress the diffusion occurring between the two phases of PLBYZST-PLZST AFE composite ceramics during sintering, the SPS method and glass-aided sintering (GAS) have been employed.133,134) As can be seen from Fig. 7(a), there is a clear split in the (002) and (200) peaks for the SPS and GAS samples compared with the case of the conventionally sintered samples, indicating reduced diffusion, which helped in improving the contributions of both the AFEO and AFET phases.134) As a result, much higher Urec were realized for the SPS (6.46 J/cm3) and GAS (5.46 J/cm3) samples compared to the conventionally sintered sample (4.65 J/cm3) that can be attributed to the increased AFE-FE transition and improved saturation polarization (Fig. 7(b)). In addition, the SPS sample displayed good temperature stability (25-125°C) relative to the other samples owing to its higher AFEO-AFET transition temperature.
It is well known that Pb-based complex perovskites such as Pb(B1/2Nb1/2)O3 (B = Lu, In, Yb, Tm) exhibit typical AFE characteristics and good temperature stability, though not many studies have been dedicated to evaluating their energy storage properties owing to their low saturation polarization. Recently, Xu et al.136) used Pb(Mg1/3Nb2/3)O3 (PMN) as a dopant to stabilize the perovskite phase and modulate the polarization and switching fields of Pb(Tm1/2Nb1/2)O3 (PTmN) ceramics. All the (1-x)PTmN-xPMN (x = 0.02-0.18) specimens exhibited the pure perovskite structure with an orthorhombic phase. Continuous decreases in the unit cell volume, structural ordering of the B-site cations, TC, and EAFE-FE and progressive improvements in Pmax and ɛr with increasing concentration of PMN were observed. This continuous increase in Pmax and the decrease in EAFE-FE led to the maximum Urec of 3.11 J/cm3 at x = 0.08, which decreased with increasing PMN concentration.
Since the AFE-FE phase transition accompanied by volumetric expansion is sensitive to the applied stress, many researchers have utilized the mechanical confining effect to improve the energy storage properties.106,121,122) Patel et al.106) reported that the application of a mechanical stress reduces hysteresis loss and increases the AFE-FE transition by suppressing FE switching and initiating domain pinning. Gradual decreases in Pr and Pmax along with an increase in the EAFE-FE of (Pb0.96La0.04)(Zr0.90Ti0.1)0.99O3 ceramics were observed with an increase in the applied mechanical stress from 20 MPa to 300 MPa, which improved the Urec and η by 38% and 25%, respectively. On the other hand, the Urec of Pb0.99Nb0.02 [(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 ceramics was enhanced by 23% (at 75 MPa) when a uniaxial stress was applied, whereas 17% (at 90 MPa) enhancement was observed for the application of a radial compressive stress.122) In another study, Young et al.121) demonstrated that mechanical self-confinement led to an improvement in the energy storage density of partially electroded Pb0.99Nb0.02[(Zr0.57Sn0.43)1-yTiy]0.98O3 (y = 0.050-0.064) ceramics. A phase-field model was used to simulate the coevolution of polarization and stress and revealed that the partially electroded sample (0.5A) exhibited a larger Pmax along with a higher as well as steeper AFE-FE transition than the fully electroded sample (1.0A), as shown in Fig. 7(c). The possible reasons for the enhanced properties such as larger polarization is due to the electrostatic fringe effect and the higher AFE-FE transition that is a result of the combined effect of mechanical self-confinement and relatively low defect concentration. The simulated stress distribution of the 0.5 A sample under the peak electric field (~ 70 kV/cm) is shown in Fig. 7(d), and the maximum stress that the sample experienced is approximately 30 MPa. All these effects resulted in a 9.2% enhancement in Urec (1.30 J/cm3 for the 0.5A sample and 1.19 J/cm3 for the 1.0A sample), though the η remained unchanged.

2.5.2. Lead-free AFE ceramics

Quite a few lead-free ceramics exhibit AFE behavior at RT; among them, (Bi, Na)TiO3 (BNT)-based138-151) and AgNbO3 (AN)-based152-156) ceramics have been extensively studied for energy storage applications. It is well known that BNT undergoes a structural transition from the rhombohedral phase to the tetragonal phase via an intermediate AFE-like phase at around 190°C (depolarization temperature, Td); however, this can be shifted to a lower temperature through compositional modification. In this regard, BT-modified BNT system has been extensively studied to stabilize the AFE phase by modulating the FE-AFE transition temperature.157) Li et al.143) modulated the antiferroelectricity and corresponding energy storage properties of 0.94Bi0.5-xNa0.5-xTiO3-0.06BaTiO3 (BNTx-BT) ceramics by tailoring the Bi/Na ratio. The composition corresponding to excess amounts of Bi3+ and/or deficiency in Na+ displayed a reduced Td with a well-developed AFE-like phase at RT, which resulted in double hysteresis loops with enhanced saturation polarization. As a result, a maximum energy storage density of 1.76 J/cm3 was achieved for x = 0.05 of the BNTx-BT ceramics.
Xu et al.144) reported that Pr and EC decreased while the BDS and ac-resistivity increased with the incorporation of La3+ in the BNT-BT matrix (i.e., [(Bi0.5Na0.5)0.93Ba0.07]1-xLax-TiO3, BNBLT7). In this study, two kinds of dopants, namely La2O3 (x = 0-0.04) and La(NO3)3 (x = 0.04) powders, were used. Since the ionic radius of La3+ (1.06 Å) is smaller than those of Bi3+ (1.36 Å) and Na+ (1.39 Å), shifting of diffraction peaks towards higher angles and a reduction in grain size were noticed with increasing La3+ concentration. Moreover, decreases in Pr from 44.90 μC/cm2 to 2.19 μC/cm2, EC from 34.0 kV/cm to 5.70 kV/cm, and an increase in the amount of the AFE-like phase of the BNBLT ceramics upon shifting the Td to below RT were observed. Consequently, improved energy storage densities of 1.09 J/cm3 (at 80 kV/cm) and 1.21 J/cm3 (at 100 kV/cm) were realized in La2O3 and La(NO3)3) doped BNT-BT samples, respectively. In another study, Li et al.147) reported that the incorporation of La3+ changed the crystal structure of BNT-BT ceramics from the FE rhombohedral phase to the AFE-like tetragonal phase and reduced the Pr and Pmax progressively. The La3+-modified BNT-BT ((Bi1/2Na1/2)0.94Ba0.06]La(1-x)ZrxTiO3, BNBLT6) ceramics exhibited a maximum strain of 0.53% and a strain coefficient of 707 pm/V for x = 0.03, while a larger Urec of 1.66 J/cm3 at 105 kV/cm was obtained for x = 0.05. Furthermore, addition of Zr increased the BDS and reduced the hysteresis loss of the BNBLT ceramics, thus, the energy storage properties were significantly improved.139,141) Recently, Kandula et al.149) investigated the effect of Nd3+ on the energy storage properties of BNT-BT AFE ceramics. The doping of 1 mol% Nd3+ in the BNT-BT matrix induced relaxor-like behavior (γ = 1.84) with improved permittivity (~ 3500@5kHz at Tm). With increasing temperature, both Urec and η gradually increased due to the increase in domain wall mobility and the ease of domain reorientation, which resulted in the large value of Urec of ~ 1.53 J/cm3 and an η of 93% at 73 kV/cm and 105°C.
Cao et al.138) demonstrated defect dipole-induced slim and double hysteresis loop behavior in the Mn2+-doped 0.7[0.94NBT-0.06BT]-0.3ST (NBBST) ternary system for enhanced energy storage properties. It was reported that the incorporation of the acceptor-type Mn2+ dopant for substituting Ti4+ resulted in the formation of oxygen vacancies to ensure charge balance and the production of defect dipoles (PD). According to the symmetry-conforming property of point defects, the symmetry of PD follows the crystal symmetry under the equilibrium condition. On application of an external electric field, PS tries to align in the direction of the field, but PD shows resistance to such a change (Fig. 7(e)). Moreover, PD can act as an internal electric field and help the new domains get back to their original state after the field is removed. Therefore, Mn2+-doped NBBST ceramics exhibit double hysteresis loop behavior with enlarged Pmax - Pr values (Fig. 7(f) and 7(g)). As a consequence, a maximum value of Urec (1.06 J/cm3 at 95 kV/cm) was obtained at 11 mol% Mn doping due to the large Pmax - Pr value (37 μC/cm2). Mishra et al.145) investigated the energy storage properties of BiFeO3 (BF) and K0.5Na0.5NbO3 (KNN) modified BNT-BT ceramics. In order to reduce the leakage current, 0.1 wt% of MnO2 was added to all the ceramics. The ternary system with the composition of 0.50BNTBT-0.50BFBT was optimal on account of its better energy storage properties (Urec = 0.77 J/cm3 and η = 67% at 50 kV/cm) compared to the other systems such as 0.25BNTBT-0.75BFBT and 0.75BNTBT-0.25BFBT. Further, doping of 1 mol% KNN to the optimized composition significantly increased the η from 67% to 90.3% at the cost of Urec (0.38 J/cm3). In addition, the 0.50BNTBT-0.50BFBT ceramics sintered using the SPS technique displayed a Urec of 1.3 J/cm3, which was 69% larger than that of the CS sample.
The other doped BNT system of (Bi, Na)TiO3-(Bi, K)TiO3 (BNT-BKT or BNKT) has been extensively studied owing to its enhanced piezoelectric and ferroelectric properties at the rhombohedral-tetragonal MPB. A few attempts have been made to improve the energy storage density properties of BNT-BKT ceramics by doping and/or forming ternary solid solutions with other perovskites.140,142,146,148) Zhao et al.140) reported that the addition of KNN improved the AFE phase stability and energy storage properties of 0.84Na0.5Bi0.5TiO3-0.16K0.5Bi0.5TiO3 (0.84BNT-0.16BKT) ceramics. As the x of (1-x)(0.84BNT-0.16BKT)-xKNN ceramics was increased (x = 0-0.15), the Td gradually decreased from 140°C to 75°C due to an increase in oxygen vacancies upon the substitution of the pentavalent Nb5+ (KNN) for the tetravalent Ti4+ (BNT-BKT) sites, which facilitated the increase in the contribution of the AFE phase; therefore, the P-E loops became slim and exhibited the double hysteretic behavior at RT. The ceramic of composition x = 0.09 exhibited the maximum Urec of 1.56 J/cm3 with an η of 64.5% and good temperature stability (ΔUrec/Urec@100 °C ≤ ± 20%) due to its uniform microstructure and slim double hysteresis loops. On the other hand, doping of a complex ion (Al0.5Nb0.5)4+ improved the BDS of the BNT-BKT ceramics.142) The substitution of Al3+ and Nb5+ for Ti4+ led to the creation of oxygen vacancies, as well as cation vacancies that compensated the charge imbalance, which increased the ability to withstand larger electric fields (~ 116 kV/cm). Moreover, (Al0.5Nb0.5)4+-containing BNT-BKT ceramics revealed reduced values of Pr, Pmax, and ionic and electronic conductivities. Therefore, the Urec continuously increased with (Al0.5Nb0.5)4+ concentration and reached a maximum value of 1.41 J/cm3 at 105 kV/cm when the doping was 8 mol%. Similarly, co-doping of Li+, Nb5+, Sr2+, and Ta5+ resulted in shifting the Td to below RT, relaxor-like behavior, reduced Pr, Pmax, and EC, and enhanced BDS of the BNT-BKT ceramics.148) All these effects made it possible to achieve the largest Urec of 1.60 J/cm3 at 90 kV/cm for ((Bi0.5[(Na0.8K0.2)0.90Li0.10]0.5)0.96Sr0.04)(Ti0.975Ta0.025Nb0)O3 (BNLKSTTN-0.10/0.04/0.025/0). In addition, BNLKSTTN-0.10/0.04/0.025/0 ceramics exhibited good bipolar fatigue endurances up to 107 polarization switching cycles and good thermal stability over the temperature range 20-200°C. In another study, Yu et al.146) reported that the incorporation of BiAlO3 (BA) changed the crystal structure of 0.75BNT-0.25BKT ceramics from the tetragonal phase to the pseudocubic phase and improved the AFE order. TEM observations of BA-doped 0.75BNT-0.25BKT ceramics revealed the existence of AFE features based on the appearance of ½(ooe) spots, which belong to the in-phase a0a0c+ oxygen octahedron tilt system with P4bm space group. The incorporation of BA destroyed the long-range FE order, which is evidenced by the decrease in Pr, Pmax, and EC and the appearance of pinched and slim hysteresis loops. At the optimal composition of 0.94(0.75BNT-0.25BKT)-0.06BA, the maximum value of 1.15 J/cm3 with an η of 73.2% at 105 kV/cm has been achieved.
Recently, Li et al.150) investigated the effect of doping of the AFE material NaNbO3 (NN) on the energy storage properties of 0.7Bi0.5Na0.5TiO3-0.3Bi0.2Sr0.7TiO3 (0.7BNT-0.3BST) AFE ceramics. With the incorporation of NN, increases in the grain size and BDS and decreases in ɛr, Pmax, and hysteresis loss were observed. Additionally, the doping of NN hindered the transformation of nanopolar clusters to macropolar clusters and resulted in slim double hysteresis loops even under large applied electric fields. Therefore, the existence of relaxor and AFE behaviors with large BDS enhanced the energy storage properties (Urec ~ 1.03 J/cm3 and η ~ 85.8% at 85 kV/cm) for 1 mol% NN-doped (0.7BNT-0.3BST) ceramics.
In the family of lead-free AFE ceramics, AgNbO3 (AN) is considered as a promising AFE candidate for energy storage applications owing to its inherently higher BDS and polarization properties.152-156) Tian et al.153) demonstrated the structure-property relation and energy storage properties of AN ceramics prepared via conventional sintering. Temperature-dependent FE measurements of the AN ceramics revealed the existence of two types of polar regions, one of which was stable up to 70°C and the other was stable up to 170°C. Earlier reports suggested that the transition at 170°C represents the freezing temperature of the antipolar dipoles of the Pbcm lattice. At RT, AN ceramics exhibited the typical AFE-like double hysteresis P-E loop with a Pmax of 40 μC/cm2 and a BDS of 175 kV/cm, which led to the realization of a maximum Urec value of ~ 2.1 J/cm3, though the η was too low (< 50%). Further, Zhao et al.152) considered MnO2 doping (0-0.3 wt%) to improve the η of AN ceramics. The addition of MnO2 reduced the sintering temperature, promoted densification, and improved the dielectric properties of AN ceramics. With increasing MnO2 concentration, the Pr decreased and both the switching fields increased monotonically, while the Pmax increased first and then decreased at the turning point of x = 0.1. The reduced Pr and ΔE and enhanced Pmax at x = 0.1 resulted in the Urec increasing from 1.6 J/cm3 to 2.5 J/cm3 and η from 37% to 57%. In addition to the improved Urec and η, Mn-doped AN ceramics displayed excellent temperature stability over the temperature range 20-180°C. Inspired by the above results, various dopants such as Ta2O5,154) WO3,155) and Bi2O3156) were introduced into AN ceramics to reduce the Pr and ΔE and increase the Pmax and switching fields, which succeeded in realizing larger values of Urec (2.6-4.2 J/cm3) and η (50-86%).

3. Conclusions and Future Prospects

The recent developments in pulsed power technology and hybrid electric vehicles propel the exploration of highly efficient energy storage materials having large energy storage and power densities, sustainability, and good fatigue lives. Dielectric ceramics are of particular interest for energy storage applications owing to their moderate energy storage density, large power density, fast charging/discharging, good mechanical and temperature stability, and good fatigue endurance. In this work, an overview of the technological developments towards improving the energy storage properties of various types of dielectric ceramics, including LD, PE, FE, RFE, and AFE materials have been presented. To achieve high energy storage properties in dielectric ceramics, various approaches such as chemical modification, grain refinement, core-shell structuring, the use of special sintering techniques, multilayered structures, interfacial engineering, mechanical confinement, self-confinement, and the fabrication of materials in which different phases coexist (near the MPB) have been utilized.
Even though significant progress has been made in realizing high energy storage properties, a few challenges remain to be resolved, including obtaining high ɛr, low tanδ, high BDS, low Pr, and high Pmax in the same dielectric material. Therefore, careful control of the processing parameters and design of a new dielectric material that can balance high polarization, low hysteresis, and high BDS are highly essential. Most of the studies have concentrated on improving the BDS rather than simultaneously improving both ɛr and BDS. However, the application of large electric fields to realize large Urec causes several safety issues. Moreover, for practical applications, high η is essential along with high Urec, therefore, the fabrication of high-permittivity nano-crystalline materials and/or materials in which the RFE and AFE phases coexist are highly recommended. In addition, the fabrication of multilayered structures consisting of appropriate combinations of high permittivity and low loss (or high BDS) layers is also a feasible route to high Urec as well as high η. Recently, Xu et al.158) reported their first-principle based theoretical predictions on the energy storage features of the rare-earth element Nd-modified BiFeO3 system, which is capable of achieving very high energy densities (100-150 J/cm3) and efficiencies (80-88%) even at practically available electric fields (2000-3000 kV/cm). Likewise, several theoretical studies combined with experimental strategies are required to design a material with enormous energy storage properties. Furthermore, the development of a standard evaluation system is required for replacing the currently used static and dynamic methods.

Acknowledgments

This study was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2016R1A2B4011663).

Fig. 1
Schematic of a dielectric capacitor, wherein the separation and alignment of electric charges is accomplished by an applied electric field. The different types of dielectric materials and the key parameters used for the evaluation of their energy storage performances are also indicated.
kcers-2019-56-1-02f1.gif
Fig. 2
(a) Ragone plot showing a comparison of the power densities and energy densities of dielectric capacitors, electrochemical capacitors, and batteries. (b) Bar chart showing the number of articles published on dielectric capacitors that are related to energy storage each year for the past ten years (from 2008 to 2017) (Source: Web of Science database; Keyword searched: dielectric capacitor (filter: energy storage)).
kcers-2019-56-1-02f2.gif
Fig. 3
Electric field dependent polarization characterizations of (a) linear dielectric, (b) paraelectric, (c) normal ferroelectric, (d) relaxor ferroelectric, and (e) antiferroelectric materials. The inset shows the dipole/domain structures of the corresponding materials.6)
kcers-2019-56-1-02f3.gif
Fig. 4
P-E hysteresis loops of (a) pure and (b) Mn-doped 0.8CaTiO3-0.2CaHfO3 ceramics measured at different temperatures.14) (c) P-E loops of (1-x)SrTiO3-x Bi0.48La0.02Na0.48Li0.02Ti0.98Zr0.02O3 (x = 0-0.4) ceramics.22) (d) Frequency dependence of the dielectric properties and (e) Weibull distribution of the dielectric breakdown strength of CaTiO3 ceramics subjected to conventional sintering and spark plasma sintering (the inset shows a schematic of the layered capacitor devices). (f) Cross-sectional SEM image of the amorphous alumina coating deposited on the surface of the CaTiO3 ceramic.20)
kcers-2019-56-1-02f4.gif
Fig. 5
(a) c/a ratio (marked in black dots)-dependent energy storage density of Bi0.5Na0.5TiO3-xBaTiO3-0.1K0.5Na0.5NbO3 (x = 0.060-0.069) ceramics; here, the calculated result is indicated by the red line, whereas the linear fitting result is indicated by the blue line. The direction of arrow represents the increase in the BNT/BT ratio.43) (b) Variation in the relative density of 0.9(K0.5Na0.5)NbO3-0.1Bi(Mg2/3Nb1/3)O3-x mol% CuO (x = 0-1.5) ceramics as a function of sintering temperature. (c) and (d) illustrate the energy storage properties of 0.9KNN-0.1BMN-1.0% CuO ceramics.53)
kcers-2019-56-1-02f5.gif
Fig. 6
(a) Temperature dependence of the dielectric properties of 0.7BaTiO3-0.3BiScO3 ceramic measured at different frequencies, (b) P-E loop of the BT-BS ceramic measured at room temperature, and (c) the energy storage density of a thin BT-BS dielectric layer measured at different electric fields.61) (d) Leakage current density properties of Bi(0.5-x)Lax(Na0.82K0.18)0.5Ti0.96Zr0.02Sn0.02O3 (x = 0-0.18) ceramics, measured at room temperature.70)
kcers-2019-56-1-02f6.gif
Fig. 7
(a) XRD patterns and (b) temperature dependence of the energy storage density of (Pb0.858Ba0.1La0.02Y0.008)(Zr0.65Sn0.3Ti0.05)O3-(Pb0.97La0.02)(Zr0.9Sn0.05Ti0.05)O3 composite ceramics subjected to conventional sintering, glass-aided sintering, and spark plasma sintering.134) (c) Results of P-E modeling for fully electroded (1.0A) and partially electroded (0.5A) Pb0.99Nb0.02[(Zr0.57Sn0.43)0.95Ti0.05]0.98O3 ceramics. (d) Axisymmetric model based simulation results of the distributions of (1) ferroelectric defects, (2) radial stress, and (3) hoop stress in the partially electroded PNZST sample under the peak electric field.121) (e) Schematic illustration of the defect and crystal symmetries in the Mn-doped tetragonal structured 0.7[0.94NBT-0.06BT]-0.3ST system. P-E hysteresis loops of (f) pure and (g) Mn-doped NBBST ceramics.138)
kcers-2019-56-1-02f7.gif
Table 1
Energy Storage Properties Reported for Various Dielectric Ceramics. (Here, LD Refers to Linear Dielectric; PE, Paraelectric; RFE, Relaxor Ferroelectric; and AFE, Antiferroelectric)
Type Material Ust/Urec (J/cm3) η (%) BDS (kV/cm) Ref
LD Mn-doped CaTiO3-CaHfO3 9.5 - 1200 14)
LD Zr-doped CaTiO3 2.7 - 756 16)
LD CaTiO3 11.8 - 1188 20)
LD Bi0.48La0.02Na0.48Li0.02Ti0.98Zr0.02O3-doped SrTiO3 2.59 85 323 22)
PE ZnO-doped Ba0.3Sr0.7TiO3 3.9 - 400 25)
PE Ba0.3Sr0.7TiO3-SrTiO3 (multilayer) 2.3 220 35)
PE Al2O3 and SiO2 coated Ba0.4Sr0.6TiO3 5.09 - 493 36)
PE SiO2-coated Ba0.5Sr0.5TiO3 2 80 290 37)
FE KNbO3-doped Bi0.5Na0.5TiO3-BaTiO3 1.72 - 168 45)
FE NaNbO3-doped BaTiO3-K0.5Bi0.5TiO3 1.96 67 220 52)
FE Bi(Mg2/3Nb1/3)O3-doped K0.5Na0.5NbO3 4.02 ~ 57 400 53)
RFE BaTiO3-BiScO3 6.10 730 61)
RFE Mn-doped BaTiO3-Bi(Mg2/3Nb1/3)O3 1.70 90 210 63)
RFE Glass added BaTiO3-Bi(Mg1/2Ti1/2)O3 1.97 94 250 65)
RFE Na0.73Bi0.09NbO3-doped BaTiO3-Bi0.5Na0.5TiO3 1.70 82 172 67)
RFE La-doped Bi0.5(Na0.82K0.18)0.5Ti0.96Zr0.02Sn0.02O3 1.95 71 155 70)
RFE MgO-doped Bi0.5Na0.5TiO3-Ba0.85Ca0.15Ti0.85Zr0.1Sn0.05O3 1.62 79 190 77)
RFE BaSnO3-doped Na0.5Bi0.5TiO3 1.91 86 190 78)
RFE Ba(Zr0.2Ti0.8)O3-doped Bi0.5Na0.5TiO3-NaNbO3 1.69 78 175 83)
RFE Na0.73Bi0.09NbO3-doped Bi0.48La0.02Na0.48Li0.02Ti0.98Zr0.02O3 2.04 55 178 86)
RFE Sr(Sc0.5Nb0.5)O3-doped (K0.5Na0.5)NbO3 2.48 81 295 87)
RFE SrTiO3-doped (K0.5Na0.5)NbO3 4.03 ~ 52 400 88)
3.67 72 400
RFE ZnO-doped (K0.5Na0.5)NbO3- Sr(Sc0.5Nb0.5)O3 2.6 73 400 89)
RFE Bi(Mg2/3Nb1/3)O3-doped (K0.5Na0.5)NbO3 4.08 62 300 91)
RFE La(Mg1/2Ti1/2)O3-doped BiFeO3-BaTiO3 1.66 82 130 94)
RFE Bi0.5Na0.5TiO3-BaAl0.5Nb0.5O3-doped SrTiO3 1.89 77 190 96)
RFE (Na0.5Bi0.5)TiO3-doped SrTiO3 1.70 69 210 98)
RFE ZrO2-doped SrTiO3-(Na0.5Bi0.5)TiO3 2.84 71 285 100)
RFE Bi0.5Na0.5TiO3-Ba0.94La0.04Zr0.02Ti0.98O3-doped SrTiO3 2.83 85 320 101)
RFE BaTiO3-doped SrTiO3-Na0.5Bi0.5TiO3 1.78 77 170 102)
RFE SnO2-doped SrTiO3-Na0.5Bi0.5TiO3-BaTiO3 2.25 79 240 103)
RFE Nd-doped BiFeO3-BaTiO3 (multilayer) 1.82 41 180 95)
6.74 77 540
AFE Pb0.97La0.02(Zr0.90Sn0.05Ti0.05)O3 4.43 61 227 112)
AFE (Pb0.97La0.02)(Zr0.8Sn0.145Ti0.055)O3 4.38 ~ 72 ~ 250 118)
AFE Pb0.97La0.02(Zr0.50Sn0.44Ti0.06)O3 4.2 82 260 114)
AFE Pb0.97La0.02(Zr0.58Sn0.35Ti0.07)O3 2.35 86 ~ 120 120)
AFE Sr-doped (Pb0.97La0.02)(Zr0.75Sn0.195Ti0.055)O3 5.56 68 ~ 350 116)
AFE (Pb0.87Ba0.1La0.02)(Zr0.68Sn0.24Ti0.08)O3 3.2 - 180 127)
AFE Y-doped (Pb0.87Ba0.1La0.02) (Zr0.65Sn0.3Ti0.05)O3 2.75 71 130 131)
AFE (Pb0.858Ba0.1La0.02Y0.008)(Zr0.65Sn0.3 Ti0.05)O3-(Pb0.97La0.02)(Zr0.9Sn0.05Ti0.05)O3 4.65 ~ 60 200 132)
AFE (Pb0.858Ba0.1La0.02Y0.008)(Zr0.65Sn0.3Ti0.05)O3-(Pb0.97La0.02) (Zr0.9Sn0.05Ti0.05)O3 6.40 62 ~ 300 133)
AFE (Bi0.46Na0.46Ba0.05La0.02)Zr0.03Ti0.97 O3 1.89 - 83 141)
AFE Bi0.55Na0.45TiO3-BaTiO3 1.76 - ~ 80 143)
AFE La-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 1.66 - 105 147)
AFE AgNbO3 2.1 - 174 153)
AFE Ta-doped AgNbO3 4.2 69 240 154)
AFE MnO2-doped AgNbO3 2.5 56 150 152)
AFE W-doped AgNbO3 3.3 50 200 155)
AFE Bi-doped AgNbO3 2.45 55 175 156)

REFERENCES

1. CA. Randall, H. Ogihara, JR. Kim, GY. Yang, CS. Stringer, S. Trolier-McKinstry, and M. Lanagan, “High Temperature and High Energy Density Dielectric Materials,” pp. 346-351 In: Proceedings of the 2009 IEEE Pulsed Power Conference; IEEE, Washington, DC. 2009.
crossref
2. TD. Huan, S. Boggs, G. Teyssedre, C. Laurent, M. Cakmak, S. Kumar, and R. Ramprasad, “Advanced Polymeric Dielectrics for High Energy Density Applications,” Prog Mater Sci, 83 236-69 (2016).
crossref
3. Z. Yao, Z. Song, H. Hao, Z. Yu, M. Cao, S. Zhang, MT. Lanagan, and H. Liu, “Homogeneous/Inhomogeneous-Structured Dielectrics and Their Energy-Storage Performances,” Adv Mater, 29 [20] 1601727(2017).
crossref
4. JR. Laghari, and WJ. Sarjeant, “Energy-Storage Pulsed-Power Capacitor Technology,” IEEE Trans Power Electron, 7 [1] 251-57 (1992).
crossref
5. . Prateek, VK. Thakur, and RK. Gupta, “Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects,” Chem Rev, 116 [7] 4260-317 (2016).
crossref
6. H. Palneedi, M. Peddigari, G-T. Hwang, D-Y. Jeong, and J. Ryu, “High-Performance Dielectric Ceramic Films for Energy Storage Capacitors: Progress and Outlook,” Adv Funct Mater, 28 [42] 1803665(2018).
crossref
7. P. Barber, S. Balasubramanian, Y. Anguchamy, S. Gong, A. Wibowo, H. Gao, JH. Ploehn, and H-C. Zur Loye, “Polymer Composite and Nanocomposite Dielectric Materials for Pulse Power Energy Storage,” Materials, 2 [4] 1697-733 (2009).
crossref
8. X. Hao, “A Review on the Dielectric Materials for High Energy-Storage Application,” J Adv Dielectr, 03 [01] 1330001(2013).
crossref
9. Z-M. Dang, J-K. Yuan, S-H. Yao, and R-J. Liao, “Flexible Nanodielectric Materials with High Permittivity for Power Energy Storage,” Adv Mater, 25 [44] 6334-65 (2013).
crossref
10. Y. Shen, Y. Lin, and QM. Zhang, “Polymer Nanocomposites with High Energy Storage Densities,” MRS Bull, 40 [9] 753-59 (2015).
crossref
11. Q. Chen, Y. Shen, S. Zhang, and QM. Zhang, “Polymer-Based Dielectrics with High Energy Storage Density,” Ann Rev Mater Res, 45 [1] 433-58 (2015).
crossref
12. Z-M. Dang, M-S. Zheng, P-H. Hu, and J-W. Zha, “Dielectric Polymer Materials for Electrical Energy Storage and Dielectric Physics: A Guide,” J Adv Phys, 4 [4] 302-13 (2015).
crossref
13. A. Chauhan, S. Patel, R. Vaish, and RC. Bowen, “Anti-Ferroelectric Ceramics for High Energy Density Capacitors,” Materials, 8 [12] 8009-31 (2015).
crossref
14. DP. Shay, NJ. Podraza, and CA. Randall, “High Energy Density, High Temperature Capacitors Utilizing Mn-Doped 0.8CaTiO3-0.2CaHfO3 Ceramics,” J Am Ceram Soc, 95 [4] 1348-55 (2012).
crossref
15. J. Zheng, GH. Chen, X. Chen, QN. Li, JW. Xu, CL. Yuan, and CR. Zhou, “Dielectric Properties and Energy Storage Behaviors in ZnNb2O6-Doped Sr0.97Nd0.02TiO3 Ceramics,” J Mater Sci Mater Electron, 27 [4] 3759-64 (2016).
crossref pdf
16. HY. Zhou, XN. Zhu, GR. Ren, and XM. Chen, “Enhanced Energy Storage Density and Its Variation Tendency in CaZr x Ti1-x O3 Ceramics,” J Alloys Compd, 688 687-91 (2016).
crossref
17. ZC. Li, GH. Chen, CL. Yuan, CR. Zhou, T. Yang, and Y. Yang, “Effects of NiNb2O6 Doping on Dielectric Property, Microstructure and Energy Storage Behavior of Sr0.97La0.02TiO3 Ceramics,” J Mater Sci Mater Electron, 28 [2] 1151-58 (2017).
crossref pdf
18. Z. Yao, Q. Luo, G. Zhang, H. Hao, M. Cao, and H. Liu, “Improved Energy-Storage Performance and Breakdown Enhancement Mechanism of Mg-Doped SrTiO3 Bulk Ceramics for High Energy Density Capacitor Applications,” J Mater Sci Mater Electron, 28 [15] 11491-99 (2017).
crossref pdf
19. G. Zhao, Y. Li, H. Liu, J. Xu, H. Hao, M. Cao, and Z. Yu, “Effect of SiO2 Additives on the Microstructure and Energy Storage Density of SrTiO3 Ceramics,” J Ceram Process Res, 13 [3] 310-14 (2012).

20. HY. Zhou, XQ. Liu, XL. Zhu, and XM. Chen, “CaTiO3 Linear Dielectric Ceramics with Greatly Enhanced Dielectric Strength and Energy Storage Density,” J Am Ceram Soc, 101 [5] 1999-2008 (2017).
crossref
21. F. Zeng, M. Cao, L. Zhang, M. Liu, H. Hao, Z. Yao, and H. Liu, “Microstructure and Dielectric Properties of SrTiO3 Ceramics by Controlled Growth of Silica Shells on SrTiO3 Nanoparticles,” Ceram Int, 43 [10] 7710-16 (2017).
crossref
22. H. Yang, F. Yan, Y. Lin, and T. Wang, “Enhanced Recoverable Energy Storage Density and High Efficiency of SrTiO3-Based Lead-Free Ceramics,” Appl Phys Lett, 111 [25] 253903(2017).
crossref
23. B. Luo, X. Wang, E. Tian, H. Song, H. Wang, and L. Li, “Enhanced Energy-Storage Density and High Efficiency of Lead-Free CaTiO3-BiScO3 Linear Dielectric Ceramics,” ACS Appl Mater Interfaces, 9 [23] 19963-72 (2017).
crossref
24. NH. Fletcher, AD. Hilton, and BW. Ricketts, “Optimization of Energy Storage Density in Ceramic Capacitors,” J Phys D: Appl Phys, 29 [1] 253(1996).
crossref
25. G. Dong, S. Ma, J. Du, and J. Cui, “Dielectric Properties and Energy Storage Density in Zno-Doped Ba0.3Sr0.7TiO3 Ceramics,” Ceram Int, 35 [5] 2069-75 (2009).
crossref
26. Q. Zhang, L. Wang, J. Luo, Q. Tang, and J. Du, “Ba0.4Sr0.6TiO3/MgO Composites with Enhanced Energy Storage Density and Low Dielectric Loss for Solid-State Pulse-Forming Line,” Int J Appl Ceram Technol, 7 [s1] E124-28 (2009).
crossref
27. Z. Song, H. Liu, S. Zhang, Z. Wang, Y. Shi, H. Hao, M. Cao, Z. Yao, and Z. Yu, “Effect of Grain Size on the Energy Storage Properties of (Ba0.4Sr0.6)TiO3 Paraelectric Ceramics,” J Eur Ceram Soc, 34 [5] 1209-17 (2014).
crossref
28. Y. Shi, H. Liu, H. Hao, M. Cao, Z. Yao, Z. Song, G. Li, W. Tang, and J. Xie, “Investigation of Dielectric Properties for Ba0.4Sr0.6TiO3 Ceramics with Various Grain Sizes,” Ferroelectrics, 487 [1] 109-21 (2015).
crossref
29. Z. Song, H. Liu, H. Hao, S. Zhang, M. Cao, Z. Yao, Z. Wang, W. Hu, Y. Shi, and B. Hu, “The Effect of Grain Boundary on the Energy Storage Properties of (Ba0.4sr0.6)Tio3 Paraelectric Ceramics by Varying Grain Sizes,” IEEE Trans Ultrason Ferroelectr Freq Control, 62 [4] 609-16 (2015).
crossref
30. Z. Song, S. Zhang, H. Liu, H. Hao, M. Cao, Q. Li, Q. Wang, Z. Yao, Z. Wang, and T. Lanagan Michael, “Improved Energy Storage Properties Accompanied by Enhanced Interface Polarization in Annealed Microwave-Sintered BST,” J Am Ceram Soc, 98 [10] 3212-22 (2015).
crossref
31. YH. Huang, YJ. Wu, J. Li, B. Liu, and XM. Chen, “Enhanced Energy Storage Properties of Barium Strontium Titanate Ceramics Prepared by Sol-Gel Method and Spark Plasma Sintering,” J Alloys Compd, 701 439-46 (2017).
crossref
32. YJ. Wu, YH. Huang, N. Wang, J. Li, MS. Fu, and XM. Chen, “Effects of Phase Constitution and Microstructure on Energy Storage Properties of Barium Strontium Titanate Ceramics,” J Eur Ceram Soc, 37 [5] 2099-104 (2017).
crossref
33. Q. Jin, Y-P. Pu, C. Wang, Z-Y. Gao, and H-Y. Zheng, “Enhanced Energy Storage Performance of Ba0.4Sr0.6TiO3 Ceramics: Influence of Sintering Atmosphere,” Ceram Int, 43 S232-38 (2017).
crossref
34. XY. Ye, YM. Li, and JJ. Bian, “Dielectric and Energy Storage Properties of Mn-Doped Ba0.3Sr0.475La0.12Ce0.03TiO3 Dielectric Ceramics,” J Eur Ceram Soc, 37 [1] 107-14 (2017).
crossref
35. Y. Gao, H. Liu, Z. Yao, H. Hao, Z. Yu, and M. Cao, “Effect of Layered Structure on Dielectric Properties and Energy Storage Density in xBa0.7Sr0.3TiO3-SrTiO3 Multilayer Ceramics,” Ceram Int, 43 [11] 8418-23 (2017).
crossref
36. J. Wang, C. Xu, B. Shen, and J. Zhai, “Enhancing Energy Storage Density of (Ba, Sr)TiO3 Ceramic Particles by Coating with Al2O3 and SiO2 ,” J Mater Sci Mater Electron, 24 [9] 3309-14 (2013).
crossref
37. X. Lu, Y. Tong, H. Talebinezhad, L. Zhang, and ZY. Cheng, “Dielectric and Energy-Storage Performance of Ba0.5Sr0.5TiO3-SiO2 Ceramic-Glass Composites,” J Alloys Compd, 745 127-34 (2018).
crossref
38. YH. Huang, YJ. Wu, B. Liu, TN. Yang, JJ. Wang, J. Li, L-Q. Chen, and XM. Chen, “From Core-Shell Ba0.4Sr0.6TiO3@SiO2 Particles to Dense Ceramics with High Energy Storage Performance by Spark Plasma Sintering,” J Mater Chem A, 6 [10] 4477-84 (2018).
crossref
39. H. Yang, F. Yan, Y. Lin, and T. Wang, “Enhanced Energy Storage Properties of Ba0.4Sr0.6TiO3 Lead-Free Ceramics with Bi2O3-B2O3-SiO2 Glass Addition,” J Eur Ceram Soc, 38 [4] 1367-73 (2018).
crossref
40. G-F. Zhang, H. Liu, Z. Yao, M. Cao, and H. Hao, “Effects of Ca Doping on the Energy Storage Properties of (Sr, Ca)TiO3 Paraelectric Ceramics,” J Mater Sci Mater Electron, 26 [5] 2726-32 (2015).
crossref
41. M. Zhou, R. Liang, Z. Zhou, C. Xu, X. Nie, X. Chen, and X. Dong, “High Energy Storage Properties of (Ni1/3Nb2/3)4+ Complex-Ion Modified (Ba0.85Ca0.15)(Zr0.10Ti0.90)O3 Ceramics,” Mater Res Bull, 98 166-72 (2018).
crossref
42. X. Dong, H. Chen, M. Wei, K. Wu, and J. Zhang, “Structure, Dielectric and Energy Storage Properties of BaTiO3 Ceramics Doped with YNbO4 ,” J Alloys Compd, 744 721-27 (2018).
crossref
43. F. Gao, X. Dong, C. Mao, F. Cao, and G. Wang, “ c/a Ratio-Dependent Energy-Storage Density in (0.9-x)Bi0.5Na0.5TiO3-xBaTiO3-0.1K0.5Na0.5NbO3 Ceramics,” J Am Ceram Soc, 94 [12] 4162-64 (2011).
crossref
44. G. Viola, H. Ning, MJ. Reece, R. Wilson, TM. Correia, P. Weaver, MG. Cain, and H. Yan, “Reversibility in Electric Field-Induced Transitions and Energy Storage Properties of Bismuth-Based Perovskite Ceramics,” J Phys D: Appl Phys, 45 [35] 355302(2012).
crossref
45. Q. Xu, J. Xie, Z. He, L. Zhang, M. Cao, X. Huang, MT. Lanagan, H. Hao, Z. Yao, and H. Liu, “Energy-Storage Properties of Bi0.5Na0.5TiO3-BaTiO3-KNbO3 Ceramics Fabricated by Wet-Chemical Method,” J Eur Ceram Soc, 37 [1] 99-106 (2017).
crossref
46. VS. Puli, DK. Pradhan, DB. Chrisey, M. Tomozawa, GL. Sharma, JF. Scott, and RS. Katiyar, “Structure, Dielectric, Ferroelectric, and Energy Density Properties of (1-x)BZT-xBCT Ceramic Capacitors for Energy Storage Applications,” J Mater Sci, 48 [5] 2151-57 (2013).
crossref
47. VS. Puli, DK. Pradhan, BC. Riggs, DB. Chrisey, and RS. Katiyar, “Structure, Ferroelectric, Dielectric and Energy Storage Studies of Ba0.70Ca0.30TiO3, Ba(Zr0.20Ti0.80)O3 Ceramic Capacitors,” Integr Ferroelectr, 157 [1] 139-46 (2014).
crossref
48. Y. Zhang, Y. Li, H. Zhu, Z. Fu, and Q. Zhang, “Sintering Temperature Dependence of Dielectric Properties and Energy-Storage Properties in (Ba,Zr)TiO3 Ceramics,” J Mater Sci Mater Electron, 28 [1] 514-18 (2017).
crossref pdf
49. T. Wang, X. Wei, Q. Hu, L. Jin, Z. Xu, and Y. Feng, “Effects of ZnNb2O6 Addition on BaTiO3 Ceramics for Energy Storage,” Mater Sci Eng B, 178 [16] 1081-86 (2013).
crossref
50. R. Ma, B. Cui, M. Shangguan, S. Wang, Y. Wang, Z. Chang, and Y. Wang, “A Novel Double-Coating Approach to Prepare Fine-Grained BaTiO3@La2O3@SiO2 Dielectric Ceramics for Energy Storage Application,” J Alloys Compd, 690 438-45 (2017).
crossref
51. J-P. Ma, X-M. Chen, W-Q. Ouyang, J. Wang, H. Li, and J-L. Fang, “Microstructure, Dielectric, and Energy Storage Properties of BaTiO3 Ceramics Prepared Via Cold Sintering,” Ceram Int, 44 [4] 4436-41 (2018).
crossref
52. J. Wan, Y. Pu, C. Hui, C. Cui, and Y. Guo, “Synthesis and Characterizations of NaNbO3 Modified 0.92BaTiO3-0.08K0.5Bi0.5TiO3 Ceramics for Energy Storage Applications,” J Mater Sci Mater Electron, 29 [6] 5158-62 (2018).
crossref pdf
53. B. Qu, H. Du, Z. Yang, and Q. Liu, “Large Recoverable Energy Storage Density and Low Sintering Temperature in Potassium-Sodium Niobate-Based Ceramics for Multilayer Pulsed Power Capacitors,” J Am Ceram Soc, 100 [4] 1517-26 (2017).
crossref
54. TF. Zhang, XG. Tang, XX. Huang, QX. Liu, YP. Jiang, and QF. Zhou, “High-Temperature Dielectric Relaxation Behaviors of Relaxer-Like PbZrO3-SrTiO3 Ceramics for Energy-Storage Applications,” Energy Technol, 4 [5] 633-40 (2016).
crossref
55. AN. Bakshi, AAB. Moghal, NA. Madhar, S. Patel, and R. Vaish, “Effect of Stress on Energy Conversion and Storage Characteristics of (1-x-y)PIN-xPMN-yPT Single Crystals,” Ferroelectr Lett Sect, 42 [4-6] 107-14 (2015).
crossref
56. A. Chauhan, S. Patel, and R. Vaish, “Effect of Directional Mechanical Confinement on the Electrical Energy Storage Density in 68Pb(Mn1/3Nb2/3)O3-32PbTiO3 Single Crystals,” Ferroelectrics, 478 [1] 40-53 (2015).
crossref
57. TF. Zhang, XG. Tang, QX. Liu, YP. Jiang, XX. Huang, and QF. Zhou, “Energy-Storage Properties and High-Temperature Dielectric Relaxation Behaviors of Relaxor Ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 Ceramics,” J Phys D: Appl Phys, 49 [9] 095302(2016).
crossref
58. B. Li, Q-X. Liu, X-G. Tang, T-F. Zhang, Y-P. Jiang, W-H. Li, and J. Luo, “Antiferroelectric to Relaxor Ferroelectric Phase Transition in PbO Modified (Pb0.97La0.02)(Zr0.95Ti0.05)O3 Ceramics with a Large Energy-Density for Dielectric Energy Storage,” RSC Adv, 7 [68] 43327-33 (2017).
crossref
59. J. Gao, Y. Liu, Y. Wang, D. Wang, L. Zhong, and X. Ren, “High Temperature-Stability of (Pb0.9La0.1)(Zr0.65Ti0.35)O3 Ceramic for Energy-Storage Applications at Finite Electric Field Strength,” Scr Mater, 137 114-18 (2017).
crossref
60. HR. Jo, and CS. Lynch, “A High Energy Density Relaxor Antiferroelectric Pulsed Capacitor Dielectric,” J Appl Phys, 119 [2] 024104(2016).
crossref
61. H. Ogihara, A. Randall Clive, and S. Trolier-McKinstry, “High-Energy Density Capacitors Utilizing 0.7 BaTiO3-0.3BiScO3 Ceramics,” J Am Ceram Soc, 92 [8] 1719-24 (2009).
crossref
62. T. Wang, L. Jin, C. Li, Q. Hu, and X. Wei, “Relaxor Ferroelectric BaTiO3-Bi(Mg2/3Nb1/3)O3 Ceramics for Energy Storage Application,” J Am Ceram Soc, 98 [2] 559-66 (2014).
crossref
63. W-B. Li, D. Zhou, and L-X. Pang, “Enhanced Energy Storage Density by Inducing Defect Dipoles in Lead Free Relaxor Ferroelectric BaTiO3-Based Ceramics,” Appl Phys Lett, 110 [13] 132902(2017).
crossref
64. Q. Hu, L. Jin, T. Wang, C. Li, Z. Xing, and X. Wei, “Dielectric and Temperature Stable Energy Storage Properties of 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3 Bulk Ceramics,” J Alloys Compd, 640 416-20 (2015).
crossref
65. Q. Hu, T. Wang, L. Zhao, L. Jin, Z. Xu, and X. Wei, “Dielectric and Energy Storage Properties of BaTiO3-Bi(Mg1/2Ti1/2)O3 Ceramic: Influence of Glass Addition and Biasing Electric Field,” Ceram Int, 43 [1] 35-9 (2017).
crossref
66. L. Wu, X. Wang, and L. Li, “Lead-Free BaTiO3-Bi(Zn2/3Nb1/3)O3 Weakly Coupled Relaxor Ferroelectric Materials for Energy Storage,” RSC Adv, 6 [17] 14273-82 (2016).
crossref
67. H. Yang, F. Yan, Y. Lin, T. Wang, F. Wang, Y. Wang, L. Guo, W. Tai, and H. Wei, “Lead-Free Batio3-Bi0.5Na0.5TiO3-Na0.73Bi0.09NbO3 Relaxor Ferroelectric Ceramics for High Energy Storage,” J Eur Ceram Soc, 37 [10] 3303-11 (2017).
crossref
68. Y. Goh, B-H. Kim, H. Bae, and D-K. Kwon, “Improved Temperature Stability in Dielectric Properties of 0.8Ba-TiO3-(0.2-x)NaNbO3-xBi(Mg1/2Ti1/2)O3 Relaxors,” J Korean Ceram Soc, 53 [2] 178-83 (2016).
crossref pdf
69. L. Wu, X. Wang, and L. Li, “Core-Shell BaTiO3@BiScO3 Particles for Local Graded Dielectric Ceramics with Enhanced Temperature Stability and Energy Storage Capability,” J Alloys Compd, 688 113-21 (2016).
crossref
70. H. Yang, F. Yan, Y. Lin, and T. Wang, “Enhanced Energy-Storage Properties of Lanthanum-Doped Bi0.5Na0.5TiO3-Based Lead-Free Ceramics,” Energy Technol, 6 [2] 357-65 (2017).
crossref
71. H-P. Kim, CW. Ahn, Y. Hwang, H-Y. Lee, and W. Jo, “Strategies of a Potential Importance, Making Lead-Free Piezoceramics Truly Alternative to PZTs,” J Korean Ceram Soc, 54 [2] 86-95 (2017).
crossref pdf
72. X. Liu, C-L. Yuan, X-Y. Liu, F-H. Luo, Q. Feng, J. Xu, G-H. Chen, and C-R. Zhou, “Microstructures, Electrical Behavior and Energy-Storage Properties of Ba0.06Na0.47Bi0.47TiO3-Ln1/3NbO3 (Ln = la, Nd, Sm) Ceramics,” Mater Chem Phys, 181 444-51 (2016).
crossref
73. Q-N. Li, C-R. Zhou, J-W. Xu, L. Yang, X. Zhang, W-D. Zeng, C-L. Yuan, G-H. Chen, and G-H. Rao, “Ergodic Relaxor State with High Energy Storage Performance Induced by Doping Sr0.85Bi0.1TiO3 in Bi0.5Na0.5TiO3 Ceramics,” J Electron Mater, 45 [10] 5146-51 (2016).
crossref pdf
74. X. Zhou, C. Yuan, Q. Li, Q. Feng, C. Zhou, X. Liu, Y. Yang, and G. Chen, “Energy Storage Properties and Electrical Behavior of Lead-Free (1-x)Ba0.04Bi0.48Na0.48TiO3-xSrZrO3 Ceramics,” J Mater Sci Mater Electron, 27 [4] 3948-56 (2016).
crossref pdf
75. Y. Pu, M. Yao, L. Zhang, and P. Jing, “High Energy Storage Density of 055Bi0.5Na0.5TiO3-0.45Ba0.85Ca0.15Ti0.9-x Zr0.1Sn x O3 Ceramics,” J Alloys Compd, 687 689-95 (2016).
crossref
76. Y. Pu, L. Zhang, M. Yao, W. Ge, and M. Chen, “Improved Energy Storage Properties of Microwave Sintered 0.475BNT-0.525BCTZ-xwt%MgO Ceramics,” Mater Lett, 189 232-35 (2017).
crossref
77. Y. Pu, M. Yao, L. Zhang, and M. Chen, “Enhanced Energy Storage Density of 0.55Bi0.5Na0.5TiO3-0.45Ba0.85Ca0.15Ti0.85Zr0.1Sn0.05O3 with Mgo Addition,” J Alloys Compd, 702 171-77 (2017).
crossref
78. L. Zhang, X. Pu, M. Chen, S. Bai, and Y. Pu, “Influence of Basno3 Additive on the Energy Storage Properties of Na0.5Bi0.5TiO3-Based Relaxor Ferroelectrics,” J Eur Ceram Soc, 38 [5] 2304-11 (2018).
crossref
79. HS. Han, IK. Hong, Y-M. Kong, JS. Lee, and W. Jo, “Effect of Nb Doping on the Dielectric and Strain Properties of Lead-Free 0.94(Bi1/2Na1/2)TiO3-0.06BaTiO3 Ceramics,” J Korean Ceram Soc, 53 [2] 145-49 (2016).
crossref pdf
80. J. Hao, Z. Xu, R. Chu, W. Li, D. Juan, and F. Peng, “Enhanced Energy-Storage Properties of (1-x)[(1-y)(Bi0.5Na0.5)TiO3-y(Bi0.5K0.5)TiO3]-x(K0.5Na0.5)NbO3 Lead-Free Ceramics,” Solid State Commun, 204 19-22 (2015).
crossref
81. Q. Xu, MT. Lanagan, X. Huang, J. Xie, L. Zhang, H. Hao, and H. Liu, “Dielectric Behavior and Impedance Spectroscopy in Lead-Free BNT-BT-NBN Perovskite Ceramics for Energy Storage,” Ceram Int, 42 [8] 9728-36 (2016).
crossref
82. X. Liu, H. Du, X. Liu, J. Shi, and H. Fan, “Energy Storage Properties of BiTi0.5Zn0.5O3-Bi0.5Na0.5TiO3-BaTiO3 Relaxor Ferroelectrics,” Ceram Int, 42 [15] 17876-79 (2016).
crossref
83. W. Tang, Q. Xu, H. Liu, Z. Yao, H. Hao, and M. Cao, “High Energy Density Dielectrics in Lead-Free Bi0.5Na0.5TiO3-NaNbO3-Ba(Zr0.2Ti0.8)O3 Ternary System with Wide Operating Temperature,” J Mater Sci Mater Electron, 27 [6] 6526-34 (2016).
crossref pdf
84. Q. Xu, H. Liu, L. Zhang, J. Xie, H. Hao, M. Cao, Z. Yao, and MT. Lanagan, “Structure and Electrical Properties of Lead-Free Bi0.5Na0.5TiO3-Based Ceramics for Energy-Storage Applications,” RSC Adv, 6 [64] 59280-91 (2016).
crossref
85. Y. Yao, Y. Li, N. Sun, J. Du, X. Li, L. Zhang, Q. Zhang, and X. Hao, “Enhanced Dielectric and Energy-Storage Properties in ZnO-Doped 0.9(0.94Na0.5Bi0.5TiO3-0.06Ba-TiO3)-0.1NaNbO3 Ceramics,” Ceram Int, 44 [6] 5961-66 (2018).
crossref
86. H. Yang, F. Yan, Y. Lin, T. Wang, and F. Wang, “High Energy Storage Density over a Broad Temperature Range in Sodium Bismuth Titanate-Based Lead-Free Ceramics,” Sci Rep, 7 [1] 8726(2017).
crossref pdf
87. B. Qu, H. Du, and Z. Yang, “Lead-Free Relaxor Ferroelectric Ceramics with High Optical Transparency and Energy Storage Ability,” J Mater Chem C, 4 [9] 1795-803 (2016).
crossref
88. Z. Yang, H. Du, S. Qu, Y. Hou, H. Ma, J. Wang, J. Wang, X. Wei, and Z. Xu, “Significantly Enhanced Recoverable Energy Storage Density in Potassium-Sodium Niobate-Based Lead Free Ceramics,” J Mater Chem A, 4 [36] 13778-85 (2016).
crossref
89. B. Qu, H. Du, Z. Yang, Q. Liu, and T. Liu, “Enhanced Dielectric Breakdown Strength and Energy Storage Density in Lead-Free Relaxor Ferroelectric Ceramics Prepared Using Transition Liquid Phase Sintering,” RSC Adv, 6 [41] 34381-89 (2016).
crossref
90. Q. Chai, D. Yang, X. Zhao, X. Chao, and Z. Yang, “Lead-Free (K,Na)NbO3-Based Ceramics with High Optical Transparency and Large Energy Storage Ability,” J Am Ceram Soc, 101 [6] 2321-29 (2017).
crossref
91. T. Shao, H. Du, H. Ma, S. Qu, J. Wang, J. Wang, X. Wei, and Z. Xu, “Potassium-Sodium Niobate Based Lead-Free Ceramics: Novel Electrical Energy Storage Materials,” J Mater Chem A, 5 [2] 554-63 (2017).
crossref
92. H. Tao, and J. Wu, “Optimization of Energy Storage Density in Relaxor (K, Na, Bi)NbO3 Ceramics,” J Mater Sci Mater Electron, 28 [21] 16199-204 (2017).
crossref pdf
93. D. Zheng, R. Zuo, D. Zhang, and Y. Li, “Novel BiFeO3-BaTiO3-Ba(Mg1/3Nb2/3)O3 Lead-Free Relaxor Ferroelectric Ceramics for Energy-Storage Capacitors,” J Am Ceram Soc, 98 [9] 2692-95 (2015).
crossref
94. D. Zheng, and R. Zuo, “Enhanced Energy Storage Properties in La(Mg1/2Ti1/2)O3-Modified BiFeO3-BaTiO3 Lead-Free Relaxor Ferroelectric Ceramics within a Wide Temperature Range,” J Eur Ceram Soc, 37 [1] 413-18 (2017).
crossref
95. D. Wang, Z. Fan, D. Zhou, A. Khesro, S. Murakami, A. Feteira, Q. Zhao, X. Tan, and I. Reaney, “Bismuth Ferrite-Based Lead-Free Ceramics and Multilayers with High Recoverable Energy Density,” J Mater Chem A, 6 [9] 4133-44 (2018).
crossref
96. F. Yan, H. Yang, Y. Lin, and T. Wang, “Dielectric and Ferroelectric Properties of SrTiO3-Bi0.5Na0.5TiO3-BaAl0.5Nb0.5O3 Lead-Free Ceramics for High-Energy-Storage Applications,” Inorg Chem, 56 [21] 13510-16 (2017).
crossref
97. H. Yang, F. Yan, Y. Lin, and T. Wang, “Improvement of Dielectric and Energy Storage Properties in SrTiO3-Based Lead-Free Ceramics,” J Alloys Compd, 728 780-87 (2017).
crossref
98. C. Cui, Y. Pu, Z. Gao, J. Wan, Y. Guo, C. Hui, Y. Wang, and Y. Cui, “Structure, Dielectric and Relaxor Properties in Lead-Free ST-NBT Ceramics for High Energy Storage Applications,” J Alloys Compd, 711 319-26 (2017).
crossref
99. H. Yang, F. Yan, Y. Lin, T. Wang, L. He, and F. Wang, “A Lead Free Relaxation and High Energy Storage Efficiency Ceramics for Energy Storage Applications,” J Alloys Compd, 710 436-45 (2017).
crossref
100. C. Cui, and Y. Pu, “Improvement of Energy Storage Density with Trace Amounts of ZrO2 Additives Fabricated by Wet-Chemical Method,” J Alloys Compd, 747 495-504 (2018).
crossref
101. H. Yang, F. Yan, Y. Lin, and T. Wang, “Novel Strontium Titanate-Based Lead-Free Ceramics for High-Energy Storage Applications,” ACS Sustainable Chem Eng, 5 [11] 10215-22 (2017).
crossref
102. C. Cui, Y. Pu, and R. Shi, “High-Energy Storage Performance in Lead-Free (0.8-x)SrTiO3-0.2Na0.5Bi0.5TiO3-xBa-TiO3 Relaxor Ferroelectric Ceramics,” J Alloys Compd, 740 1180-87 (2018).
crossref
103. C. Cui, and Y. Pu, “Effect of Sn Substitution on the Energy Storage Properties of 0.45SrTiO3-0.2Na0.5Bi0.5TiO3-0.35Ba-TiO3 Ceramics,” J Mater Sci, 53 [13] 9830-41 (2018).
crossref pdf
104. X. Hao, J. Zhai, LB. Kong, and Z. Xu, “A Comprehensive Review on the Progress of Lead Zirconate-Based Antiferroelectric Materials,” Prog Mater Sci, 63 1-57 (2014).
crossref
105. E. Sawaguchi, H. Maniwa, and S. Hoshino, “Antiferroelectric Structure of Lead Zirconate,” Phys Rev, 83 [5] 1078(1951).
crossref
106. P. Satyanarayan, C. Aditya, and V. Rahul, “Enhancing Electrical Energy Storage Density in Anti-Ferroelectric Ceramics Using Ferroelastic Domain Switching,” Mater Res Exp, 1 [4] 045502(2014).
crossref
107. B. Li, Q. Liu, X. Tang, T. Zhang, Y. Jiang, W. Li, and J. Luo, “High Energy Storage Density and Impedance Response of PLZT2/95/5 Antiferroelectric Ceramics,” Materials, 10 [2] 143(2017).
crossref
108. H. Zhang, X. Chen, F. Cao, G. Wang, X. Dong, Z. Hu, and T. Du, “Charge-Discharge Properties of an Antiferroelectric Ceramics Capacitor under Different Electric Fields,” J Am Ceram Soc, 93 [12] 4015-17 (2010).
crossref
109. J. Wang, T. Yang, S. Chen, and G. Li, “High Energy Storage Density Performance of Ba, Sr-Modified Lead Lanthanum Zirconate Titanate Stannate Antiferroelectric Ceramics,” Mater Res Bull, 48 [10] 3847-49 (2013).
crossref
110. R. Xu, Z. Xu, Y. Feng, X. Wei, and J. Tian, “Nonlinear Dielectric and Discharge Properties of Pb0.94La0.04[(Zr0.56-Sn0.44)0.84Ti0.16]O3 Antiferroelectric Ceramics,” J Appl Phys, 120 [14] 144102(2016).
crossref
111. H. Yu, J. Zhang, M. Wei, J. Huang, H. Chen, and C. Yang, “Enhanced Energy Storage Density Performance in (Pb0.97La0.02)(Zr0.5Sn0.44Ti0.06)-BiYO3 Anti-Ferroelectric Composite Ceramics,” J Mater Sci Mater Electron, 28 [1] 832-38 (2017).
crossref pdf
112. J. Wang, T. Yang, S. Chen, and X. Yao, “Small Hysteresis and High Energy Storage Power of Antiferroelectric Ceramics,” Funct Mater Lett, 07 [01] 1350064(2013).
crossref
113. Z. Liu, X. Chen, W. Peng, C. Xu, X. Dong, F. Cao, and G. Wang, “Temperature-Dependent Stability of Energy Storage Properties of Pb0.97La0.02(Zr0.58Sn0.335Ti0.085)O3 Antiferroelectric Ceramics for Pulse Power Capacitors,” Appl Phys Lett, 106 [26] 262901(2015).
crossref
114. X. Wang, J. Shen, T. Yang, Y. Dong, and Y. Liu, “High Energy-Storage Performance and Dielectric Properties of Antiferroelectric (Pb0.97La0.02)(Zr0.5Sn0.5-xTi x )O3 Ceramic,” J Alloys Compd, 655 309-13 (2016).
crossref
115. C. Xu, Z. Liu, X. Chen, S. Yan, F. Cao, X. Dong, and G. Wang, “High Charge-Discharge Performance of Pb0.98La0.02-(Zr0.35Sn0.55Ti0.10)0.995O3 Antiferroelectric Ceramics,” J Appl Phys, 120 [7] 074107(2016).
crossref
116. Q. Zhang, H. Tong, J. Chen, Y. Lu, T. Yang, X. Yao, and Y. He, “High Recoverable Energy Density over a Wide Temperature Range in Sr Modified (Pb,La)(Zr,Sn,Ti)O3 Antiferroelectric Ceramics with an Orthorhombic Phase,” Appl Phys Lett, 109 [26] 262901(2016).
crossref
117. R. Xu, Z. Xu, Y. Feng, J. Tian, and D. Huang, “Energy Storage and Release Properties of Sr-Doped (Pb,La)-(Zr,Sn,Ti)O3 Antiferroelectric Ceramics,” Ceram Int, 42 [11] 12875-79 (2016).
crossref
118. Q. Zhang, Y. Dan, J. Chen, Y. Lu, T. Yang, X. Yao, and Y. He, “Effects of Composition and Temperature on Energy Storage Properties of (Pb,La)(Zr,Sn,Ti)O3 Antiferroelectric Ceramics,” Ceram Int, 43 [14] 11428-32 (2017).
crossref
119. Z. Liu, X. Dong, Y. Liu, F. Cao, and G. Wang, “Electric Field Tunable Thermal Stability of Energy Storage Properties of PLZST Antiferroelectric Ceramics,” J Am Ceram Soc, 100 [6] 2382-86 (2017).
crossref
120. Z. Liu, Y. Bai, X. Chen, X. Dong, H. Nie, F. Cao, and G. Wang, “Linear Composition-Dependent Phase Transition Behavior and Energy Storage Performance of Tetragonal PLZST Antiferroelectric Ceramics,” J Alloys Compd, 691 721-25 (2017).
crossref
121. SE. Young, JY. Zhang, W. Hong, and X. Tan, “Mechanical Self-Confinement to Enhance Energy Storage Density of Antiferroelectric Capacitors,” J Appl Phys, 113 [5] 054101(2013).
crossref
122. S. Patel, A. Chauhan, and R. Vaish, “Enhanced Electrical Energy Storage Density in Mechanical Confined Antiferroelectric Ceramic,” Ferroelectrics, 486 [1] 114-25 (2015).
crossref
123. X. Chen, H. Zhang, F. Cao, G. Wang, X. Dong, Y. Gu, H. He, and Y. Liu, “Charge-Discharge Properties of Lead Zirconate Stannate Titanate Ceramics,” J Appl Phys, 106 [3] 034105(2009).
crossref
124. Q. Zhang, X. Liu, Y. Zhang, X. Song, J. Zhu, I. Baturin, and J. Chen, “Effect of Barium Content on Dielectric and Energy Storage Properties of (Pb,La,Ba)(Zr,Sn,Ti)O3 Ceramics,” Ceram Int, 41 [2] 3030-35 (2015).
crossref
125. L. Chen, X. Hao, Q. Zhang, and S. An, “Energy-Storage Performance of PbO-B2O3-SiO2 Added (Pb0.92Ba0.05La0.02)-(Zr0.68Sn0.27Ti0.05)O3 Antiferroelectric Ceramics Prepared by Microwave Sintering Method,” J Mater Sci Mater Electron, 27 [5] 4534-40 (2016).
crossref pdf
126. R. Xu, Z. Xu, Y. Feng, H. He, J. Tian, and D. Huang, “Temperature Dependence of Energy Storage in Pb0.90La0.04Ba0.04-[(Zr0.7Sn0.3)0.88Ti0.12]O3 Antiferroelectric Ceramics,” J Am Ceram Soc, 99 [9] 2984-88 (2016).
crossref
127. G. Zhang, D. Zhu, X. Zhang, L. Zhang, J. Yi, B. Xie, Y. Zeng, Q. Li, Q. Wang, and S. Jiang, “High-Energy Storage Performance of (Pb0.87Ba0.1La0.02)(Zr0.68Sn0.24Ti0.08)O3 Antiferroelectric Ceramics Fabricated by the Hot-Press Sintering Method,” J Am Ceram Soc, 98 [4] 1175-81 (2015).
crossref
128. X. Wang, J. Shen, T. Yang, Z. Xiao, and Y. Dong, “Phase Transition and Energy Storage Performance in Ba-Doped PLZST Antiferroelectric Ceramics,” J Mater Sci Mater Electron, 26 [11] 9200-4 (2015).
crossref
129. G. Zhang, P. Liu, B. Fan, H. Liu, Y. Zeng, S. Qiu, S. Jiang, Q. Li, Q. Wang, and J. Liu, “Large Energy Density in Ba Doped Pb0.97La0.02(Zr0.65Sn0.3Ti0.05)O3 Antiferroelectric Ceramics with Improved Temperature Stability,” IEEE Trans Dielectr Electr Insul, 24 [2] 744-48 (2017).
crossref
130. B. Guo, P. Liu, Y. Song, and D. Liu, “Effect of Ti Content on Energy Storage Properties of (Pb0.87Ba0.10La0.02)-(Zr0.60Sn0.40-x Ti x )O3 Bulk Ceramics,” Ferroelectrics, 510 [1] 152-60 (2017).
crossref
131. L. Zhang, S. Jiang, Y. Zeng, M. Fu, K. Han, Q. Li, Q. Wang, and G. Zhang, “Y Doping and Grain Size Co-Effects on the Electrical Energy Storage Performance of (Pb0.87Ba0.1La0.02)(Zr0.65Sn0.3Ti0.05)O3 Anti-Ferroelectric Ceramics,” Ceram Int, 40 [4] 5455-60 (2014).
crossref
132. L. Zhang, S. Jiang, B. Fan, and G. Zhang, “High Energy Storage Performance in (Pb0.858Ba0.1La0.02Y0.008)(Zr0.65Sn0.3Ti0.05)O3-(Pb0.97La0.02)(Zr0.9Sn0.05Ti0.05)O3 Anti-Ferroelectric Composite Ceramics,” Ceram Int, 41 [1] 1139-44 (2015).
crossref
133. L. Zhang, S. Jiang, B. Fan, and G. Zhang, “Enhanced Energy Storage Performance in (Pb0.858Ba0.1La0.02Y0.008)-(Zr0.65Sn0.3Ti0.05)O3-(Pb0.97La0.02)(Zr0.9Sn0.05Ti0.05)O3 Anti-Ferroelectric Composite Ceramics by Spark Plasma Sintering,” J Alloys Compd, 622 162-65 (2015).
crossref
134. J. Yi, L. Zhang, B. Xie, and S. Jiang, “The Influence of Temperature Induced Phase Transition on the Energy Storage Density of Anti-Ferroelectric Ceramics,” J Appl Phys, 118 [12] 124107(2015).
crossref
135. Q. Zhang, J. Chen, Y. Lu, T. Yang, X. Yao, and Y. He, “(Pb,Sm)(Zr,Sn,Ti)O3 Multifunctional Ceramics with Large Electric-Field-Induced Strain and High-Energy Storage Density,” J Am Ceram Soc, 99 [12] 3853-56 (2016).
crossref
136. L. Xu, C. He, X. Yang, Z. Wang, X. Li, HN. Tailor, and X. Long, “Composition Dependent Structure, Dielectric and Energy Storage Properties of Pb(Tm1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3 Antiferroelectric Ceramics,” J Eur Ceram Soc, 37 [10] 3329-34 (2017).
crossref
137. D. Berlincourt, “Transducers Using Forced Transitions between Ferroelectric and Antiferroelectric States,” IEEE Trans Sonics Ultrason, 13 [4] 116-24 (1966).
crossref
138. W. Cao, W. Li, Y. Feng, T. Bai, Y. Qiao, Y. Hou, T. Zhang, Y. Yu, and W. Fei, “Defect Dipole Induced Large Recoverable Strain and High Energy-Storage Density in Lead-Free Na0.5Bi0.5TiO3-Based Systems,” Appl Phys Lett, 108 [20] 202902(2016).
crossref
139. Y. Wang, Z. Lv, H. Xie, and J. Cao, “High Energy-Storage Properties of [(Bi1/2Na1/2)0.94Ba0.06]La(1-x)Zr x TiO3 Lead-Free Anti-Ferroelectric Ceramics,” Ceram Int, 40 [3] 4323-26 (2014).
crossref
140. J. Zhao, M. Cao, Z. Wang, Q. Xu, L. Zhang, Z. Yao, H. Hao, and H. Liu, “Enhancement of Energy-Storage Properties of K0.5Na0.5NbO3 Modified Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3 Lead-Free Ceramics,” J Mater Sci Mater Electron, 27 [1] 466-73 (2016).
crossref pdf
141. J. Cao, Y. Wang, and Z. Li, “Energy-Storage Properties and Electrical Behavior of Lead-Free Anti-Ferroelectric (Bi0.46Na0.46Ba0.05La0.02)Zr x Ti(1-x)O3 Ceramics,” Ferroelectrics, 505 [1] 17-23 (2016).
crossref
142. Y. Zhao, J. Xu, L. Yang, C. Zhou, X. Lu, C. Yuan, Q. Li, G. Chen, and H. Wang, “High Energy Storage Property and Breakdown Strength of Bi0.5(Na0.82K0.18)0.5TiO3 Ceramics Modified by (Al0.5Nb0.5)4+ Complex-Ion,” J Alloys Compd, 666 209-16 (2016).
crossref
143. Q. Li, C. Zhou, J. Xu, L. Yang, X. Zhang, W. Zeng, C. Yuan, G. Chen, and G. Rao, “Tailoring Antiferroelectricity with High Energy-Storage Properties in Bi0.5Na0.5TiO3-BaTiO3 Ceramics by Modulating Bi/Na Ratio,” J Mater Sci Mater Electron, 27 [10] 10810-15 (2016).
crossref pdf
144. J. Xu, X. Lu, L. Yang, C. Zhou, Y. Zhao, H. Zhang, X. Zhang, W. Qiu, and H. Wang, “Enhanced Electrical Energy Storage Properties in La-Doped (Bi0.5Na0.5)0.93Ba0.07TiO3 Lead-Free Ceramics by Addition of La2O3 and La(NO3)3 ,” J Mater Sci, 52 [17] 10062-72 (2017).
crossref pdf
145. A. Mishra, B. Majumdar, and R. Ranjan, “A Complex Lead-Free (Na,Bi,Ba)(Ti,Fe)O3 Single Phase Perovskite Ceramic with a High Energy-Density and High Discharge-Efficiency for Solid State Capacitor Applications,” J Eur Ceram Soc, 37 [6] 2379-84 (2017).
crossref
146. Z. Yu, Y. Liu, M. Shen, H. Qian, F. Li, and Y. Lyu, “Enhanced Energy Storage Properties of BiAlO3 Modified Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 Lead-Free Antiferroelectric Ceramics,” Ceram Int, 43 [10] 7653-59 (2017).
crossref
147. F. Li, Y. Liu, Y. Lyu, Y. Qi, Z. Yu, and C. Lu, “Huge Strain and Energy Storage Density of A-site La3+ Donor Doped (Bi0.5Na0.5)0.94Ba0.06TiO3 Ceramics,” Ceram Int, 43 [1] 106-10 (2017).
crossref
148. J. Yin, X. Lv, and J. Wu, “Enhanced Energy Storage Properties of {Bi0.5[(Na0.8K0.2)1-z Li z ]0.5}0.96Sr0.04(Ti1-x-y Ta x Nb y )O3 Lead-Free Ceramics,” Ceram Int, 43 [16] 13541-46 (2017).
crossref
149. KR. Kandula, K. Banerjee, SSK. Raavi, and S. Asthana, “Enhanced Electrocaloric Effect and Energy Storage Density of Nd-Substituted 0.92NBT-0.08BT Lead Free Ceramic,” Phys Status Solidi A, 215 [7] 1700915(2018).
crossref
150. Q. Li, Z. Yao, L. Ning, S. Gao, B. Hu, G. Dong, and H. Fan, “Enhanced Energy-Storage Properties of (1-x)(0.7Bi0.5Na0.5TiO3-0.3Bi0.2Sr0.7TiO3)-xNaNbO3 Lead-Free Ceramics,” Ceram Int, 44 [3] 2782-88 (2018).
crossref
151. P. Chen, and B. Chu, “Improvement of Dielectric and Energy Storage Properties in Bi(Mg1/2Ti1/2)O3-Modified (Na1/2Bi1/2)0.92Ba0.08TiO3 Ceramics,” J Eur Ceram Soc, 36 [1] 81-8 (2016).
crossref
152. L. Zhao, Q. Liu, S. Zhang, and J-F. Li, “Lead-Free AgNbO3 Anti-Ferroelectric Ceramics with an Enhanced Energy Storage Performance Using MnO2 Modification,” J Mater Chem C, 4 [36] 8380-84 (2016).
crossref
153. Y. Tian, L. Jin, H. Zhang, Z. Xu, X. Wei, ED. Politova, SY. Stefanovich, NV. Tarakina, I. Abrahams, and H. Yan, “High Energy Density in Silver Niobate Ceramics,” J Mater Chem A, 4 [44] 17279-87 (2016).
crossref
154. L. Zhao, Q. Liu, J. Gao, S. Zhang, and J-F. Li, “Lead-Free Antiferroelectric Silver Niobate Tantalate with High Energy Storage Performance,” Adv Mater, 29 [31] 1701824(2017).
crossref
155. L. Zhao, J. Gao, Q. Liu, S. Zhang, and J-F. Li, “Silver Niobate Lead-Free Antiferroelectric Ceramics: Enhancing Energy Storage Density by B-site Doping,” ACS Appl Mater Interfaces, 10 [1] 819-26 (2018).
crossref
156. Y. Tian, L. Jin, H. Zhang, Z. Xu, X. Wei, G. Viola, I. Abrahams, and H. Yan, “Phase Transitions in Bismuth-Modified Silver Niobate Ceramics for High Power Energy Storage,” J Mater Chem A, 5 [33] 17525-31 (2017).
crossref
157. BW. Eerd, D. Damjanovic, N. Klein, N. Setter, and J. Trodahl, “Structural Complexity of (Na0.5Bi0.5)TiO3-BaTiO3 as Revealed by Raman Spectroscopy,” Phys Rev B, 82 [10] 104112(2010).
crossref
158. B. Xu, J. Íñiguez, and L. Bellaiche, “Designing Lead-Free Antiferroelectrics for Energy Storage,” Nat Commun, 8 15682(2017).
crossref
TOOLS
PDF Links  PDF Links
PubReader  PubReader
ePub Link  ePub Link
Full text via DOI  Full text via DOI
Download Citation  Download Citation
CrossRef TDM  CrossRef TDM
  E-Mail
  Print
Share:      
METRICS
0
Crossref
0
Scopus
793
View
64
Download
Related article
Editorial Office
Meorijae Bldg., Suite # 403, 76, Bangbae-ro, Seocho-gu, Seoul 06704, Korea
TEL: +82-2-584-0185   FAX: +82-2-586-4582   E-mail: ceramic@kcers.or.kr
About |  Browse Articles |  Current Issue |  For Authors and Reviewers
Copyright © The Korean Ceramic Society. All rights reserved.                      developed in m2community