Domain size and charge defects affecting the polarization switching of antiferroelectric domains

The switching behavior of antiferroelectric domain structures under the applied electric field is not fully understood.In this work,by using the phase field simulation,we have studied the polarization switching property of antiferroelectric domains.Our results indicate that the ferroelectric domains nucleate preferably at the boundaries of the antiferroelectric domains,and antiferroelectrics with larger initial domain sizes possess a higher coercive electric field as demonstrated by hysteresis loops.Moreover,we introduce charge defects into the sample and numerically investigate their influence.It is also shown that charge defects can induce local ferroelectric domains,which could suppress the saturation polarization and narrow the enclosed area of the hysteresis loop.Our results give insights into understanding the antiferroelectric phase transformation and optimizing the energy storage property in experiments.

Manufacture of large displacement antiferroelectric ceramic and its properties

Reduced and internally biased oxide wafer (RAINBOW) Pb (Sn, Zr, Ti) O3 (PSZT) antiferroelectric ceramics are fabricated by chemical reduction. It is a kind of large displacement actuating materials composed of reduced and unreduced layers. It is found that PSZT is easily reduced and the optimal conditions for producing RAINBOW samples are determined to be 870°C for 2 to 3 h, which results in a reduced layer composed of metallic lead and refractory oxides (PbO, ZrO2 and ZrTiO4). The phase transitions from antiferroelectric state to ferroelectric state occur at lower field strength in RAINBOW samples compared with normal PSZT ceramics. Larger axial displacement is also obtained from RAINBOW samples by application of electric fields exceeding the phase switching level. However, the actuating properties of RAINBOW samples are dependent on the manner of applying load on it.

Electromechanical-induced antiferroelectric-ferroelectric phase transition in PbLa(Zr,Sn,Ti)O_3 ceramic

Antiferroelectric ferroelectric （AFE-FE） phase transition in ceramic Pbo.97Lao.02（Zro.75Snon36Tion14）O3 （PLZST） was studied by dielectric spectroscopy as functions of frequency （102-105 Hz） and pressure （0-500 MPa） under a DC electric field. The hydrostatic pressure-dependent remnant polarization and dielectric constant were mea- sured. The results show that remnant polarization of the metastable rhombohedral ferroelectric PLZST poled ceramic decreases sharply and depoles completely at phase transition under hydrostatic pressure. The dielectric constant um dergoes an abrupt jump twice during a load and unload cycle under an electric field. The two abrupt jumps correspond to two phase transitions, FE AFE and AFE-FE.

Enhanced energy storage behaviors in free-standing antiferroelectric Pb(Zr_(0.95)Ti_(0.05))O_3 thin membranes

Free-standing antiferroelectric Pb（Zr0.95Ti0.05O3（PZT（95/5）） thin film is fabricated on 200-nm-thick Pt foil by using pulsed laser deposition.X-ray diffraction patterns indicate that free-standing PZT（95/5） film possesses an α-axis preferred orientation.The critical electric field for the 300-nm-thick free-standing PZT（95/5） film transiting from antiferroelectric to ferroelectric phases is increased to 770 kV/cm,but its saturation polarization remains almost unchanged as compared with that of the substrate-clamped PZT（95/5） film.The energy storage density and energy efficiency of the substrate-clamped PZT（95/5） film are 6.49 J/cm^3 and 54.5%,respectively.In contrast,after removing the substrate,the energy storage density and energy efficiency of the free-standing PZT（95/5） film are enhanced up to 17.45 J/cm^3 and 67.9%,respectively.

Effects of precursor solution concentration on dielectric properties of (Pb,La)(Zr,Ti)O_3 antiferroelectric thick films by sol-gel processing

Pb0.97La0.02Zr0.95Ti0.05O3(PLZT)antiferroelectric thick films derived from different precursor solution concentrations are prepared on platinized silicon substrates by sol-gel processing.The films present polycrystalline perovskite structure with a(100)preferred orientation by X-ray diffraction(XRD)analysis.The antiferroelectricity of the films is confirmed by the double hysteresis behaviors of polarization and double-bufferfly response of dielectric constant under the applied electrical field.Antiferroelectric properties and dielectric constant are improved while the polarization characteristic values are reduced with the increase of precursor solution concentration.The films at higher precursor solution concentration exhibit excellent dielectric properties.

FABRICATION AND PROPERTIES OF ANTIFERROELECTRIC RAINBOW ACTUATOR

A new type of large-displacement actuator called reduced and internally biased oxide wafer （RAINBOW） is fabricated by chemical reduction of Pb（Sn, Zr, Ti）O3（PSZT） antiferroelectric ceramics and its properties are investigated. It is found that PSZT is easily reduced and the optimal conditions for producing RAINBOW samples are determined to be 870 ℃ for 2-3 h. The antiferroelectrics-ferroelectrics phase transitions occur at lower field strength in RAINBOW actuators compared with normal PSZT actuators. Large axial displacements are also obtained from the RAINBOW actuator by application of electric fields exceeding the phase switching level. However, the field-induced displacement of the RAINBOW actuator is dependent on the manner of applying load on the samples.

Relaxor antiferroelectric-relaxor ferroelectric crossover in NaNbO_(3)-based lead-free ceramics for high-efficiency large-capacitive energy storage

Relaxor ferroic dielectrics have garnered increasing attention in the past decade as promising materials for energy storage.Among them,relaxor antiferroelectrics(AFEs)and relaxor ferroelectrics(FEs)have shown great promise in term of high energy storage density and efficiency,respectively.In this study,a unique phase transition from relaxor AFE to relaxor FE was achieved for the first time by introducing strong-ferroelectricity BaTiO_(3)into NaNbO_(3)-BiFeO_(3)system,leading to an evolution from AFE R hierarchical nanodomains to FE polar nanoregions.A novel medium state,consisting of relaxor AFE and relaxor FE,was identified in the crossover of 0.88NaNbO_(3)–0.07BiFeO_(3)–0.05BaTiO_(3)ceramic,exhibiting a distinctive core-shell grain structure due to the composition segregation.By harnessing the advantages of high energy storage density from relaxor AFE and large efficiency from relaxor FE,the ceramic showcased excellent overall energy storage properties.It achieved a substantial recoverable energy storage density W_(rec)~13.1 J/cm^(3)and an ultrahigh efficiencyη~88.9%.These remarkable values shattered the trade-off relationship typically observed in most dielectric capacitors between W_(rec)andη.The findings of this study provide valuable insights for the design of ceramic capacitors with enhanced performance,specifically targeting the development of next generation pulse power devices.

Designing silver niobate-based relaxor antiferroelectrics for ultrahigh energy storage performance

AgNbO_(3)(AN)and modified AgNbO_(3) have been extensively investigated as promising lead-free antiferroelectric(AFE)energy storage materials.Previous studies have focused mainly on the use of an ion dopant at the A/B site to obtain a stabilized AFE phase;however,simultaneous improvements in the recoverable energy storage density(Wrec)and efficiency(n)are stll difficult to realize.Herein,we innovatively constructed a AgNbO_(3)-NaNbO_(3)-(Sr_(0.7)Bi_(0.2))TiO_(3)(AN-NN-SBT)ternary solid solution to achieve a relaxor AFE in AgNbO_(3)-based materials.The coexistence of antiferroelectric(M3)and paraelectric(O)phases in 0.8(0.7AgNbO_(3)-0.3NaNbO_(3))-0.2(Sro.7Bio.2)TiO_(3) confirms the successful realization of a relaxor AFE,attributed to multiple ion occupation at the A/B sites.Consequently,a high Wrec of 7.53 J.cm^(-3) and n of 74.0% are acquired,together with superior stability against various temperatures,frequencies,and cycling numbers.Furthermore,a high power density(298.7 MW·cm^(-3))and fast discharge speed(41.4 ns)are also demonstrated for the AgNbO_(3)-based relaxor AFE.This work presents a promising energy storage AgNbO_(3)-based ternary solid solution and proposes a novel strategy for AgNbO_(3)-based energy storage via the design of relaxor AFE materials.

High energy storage density in NaNbO_(3) antiferroelectrics with double hysteresis loop

Antiferroelectrics(AFEs)possess great potential for high performance dielectric capacitors,due to their distinct double hysteresis loop with high maximum polarization and low remnant polarization.However,the well-known NaNbO3 lead-free antiferroelectric(AFE)ceramic usually exhibits square-like P–E loop related to the irreversible AFE P phase to ferroelectric(FE)Q phase transition,yielding low recoverable energy storage density(Wrec).Herein,significantly improved Wrec up to 3.3 J/cm^(3) with good energy storage efficiency(η)of 42.4% was achieved in Na_(0.7)Ag_(0.3)Nb_(0.7)Ta_(0.3)O_(3)(30Agsingle bond30Ta)ceramic with well-defined double P–E loop,by tailoring the A-site electronegativity with Ag+and B-site polarizability with Ta^(5+).The Transmission Electron Microscope,Piezoresponse Force Microscope and in-situ Raman spectra results verified a good reversibility between AFE P phase and high-field-induced FE Q phase.The improved stability of AFE P phase,being responsible for the double P–E loop and improved Wrec,was attributed to the decreased octahedral tilting angles and cation displacements.This mechanism was revealed by synchrotron X-ray diffraction and Scanning Transmission Electron microscope.This work provides a good paradigm for achieving double P–E loop and high energy storage density in NaNbO_(3)-based ceramics.

Substitution of Pb with (Li_(1/2)Bi_(1/2)) in PbZrO_(3)-based antiferroelectric ceramics

PbZrO_(3)-based antiferroelectric(AFE)ceramics are promising dielectrics for high-energy-density capacitors due to their reversible phase transitions during charge-discharge cycles.In this work,a new composition series,[Pb_(0.93-x)La_(0.02)(Li_(1/2)Bi_(1/2))_(x)Sr_(0.04)][Zr_(0.57)Sn_(0.34)Ti_(0.09)]O_(3),with Li^(+)and Bi^(3+)substitution of Pb^(2+)at x=0,0.04,0.08,0.12,0.16 is investigated for the microstructure evolution,ferroelectric(FE)and dielectric properties.It is found that Li^(+) and Bi^(3+) substitution can significantly reduce the sintering temperature and simultaneously enhance the dielectric breakdown strength.An ultrahigh energy efficiency(94.0%)and a large energy density(3.22 J/cm^(3))are achieved in the composition of x=0.12 with a low sintering temperature(1075℃).

Achieving a high energy storage density in Ag(Nb,Ta)O_(3) antiferroelectric films via nanograin engineering

Due to its lead-free composition and a unique double polarization hysteresis loop with a large maximum polarization(Pmax)and a small remnant polarization(Pr),AgNbO_(3)-based antiferroelectrics(AFEs)have attracted extensive research interest for electric energy storage applications.However,a low dielectric breakdown field(Eb)limits an energy density and its further development.In this work,a highly efficient method was proposed to fabricate high-energy-density Ag(Nb,Ta)O_(3) capacitor films on Si substrates,using a two-step process combining radio frequency(RF)-magnetron sputtering at 450℃and post-deposition rapid thermal annealing(RTA).The RTA process at 700℃led to sufficient crystallization of nanograins in the film,hindering their lateral growth by employing short annealing time of 5 min.The obtained Ag(Nb,Ta)O_(3) films showed an average grain size(D)of~14 nm(obtained by Debye-Scherrer formula)and a slender room temperature(RT)polarization-electric field(P-E)loop(Pr≈3.8 mC·cm^(−2) and P_(max)≈38 mC·cm^(−2) under an electric field of~3.3 MV·cm^(−1)),the P-E loop corresponding to a high recoverable energy density(W_(rec))of~46.4 J·cm^(−3) and an energy efficiency(η)of~80.3%.Additionally,by analyzing temperature-dependent dielectric property of the film,a significant downshift of the diffused phase transition temperature(T_(M2-M3))was revealed,which indicated the existence of a stable relaxor-like AFE phase near the RT.The downshift of the T_(M2-M3) could be attributed to a nanograin size and residual tensile strain of the film,and it led to excellent temperature stability(20-240℃)of the energy storage performance of the film.Our results indicate that the Ag(Nb,Ta)O_(3) film is a promising candidate for electrical energy storage applications.

Review on field-induced phase transitions in lead-free NaNbO_(3)-based antiferroelectric perovskite oxides for energy storage

Emerging new applications of antiferroelectric perovskite oxides based on their fascinating phase transformation between polar and nonpolar states have provided considerable attention to this class of materials even decades after the discovery of antiferroelectricity.After presenting the challenge of formulating a precise definition of antiferroelectric materials,we briefly summarize proposed applications.In the following,we focus on the crystallographic structures of the antiferroelectric and ferroelectric phases of NaNbO_(3),which is emerging as a promising alternative to PbZrO_(3)-based systems.The field-induced phase transition behavior of NaNbO_(3)-based AFE materials in the form of single crystals,bulk ceramics,and multilayer ceramic capacitors is reviewed.Recent advances in a group of materials exhibiting high energy storage performance and relaxor-like behavior are also covered.The influence of electrode geometry on phase transition behavior and thus on the energy storage property is briefly addressed.The review concludes with an overview of the remaining challenges related to the fundamental understanding of the scientific richness of AFE materials in terms of structure,microstructure,defect transport under high fields,and phase transition dynamics required for their future development and applications.

Ultrahigh energy storage performance realized in AgNbO_(3)-based antiferroelectric materials via multiscale engineering

Antiferroelectric(AFE)materials are promising for the applications in advanced high-power electric and electronic devices.Among them,AgNbO_(3)(AN)-based ceramics have gained considerable attention due to their excellent energy storage performance.Herein,multiscale synergistic modulation is proposed to improve the energy storage performance of AN-based materials,whereby the multilayer structure is employed to improve the breakdown strength(Eb),and Sm/Ta doping is utilized to enhance the AFE stability.As a result,ultrahigh recoverable energy storage density(Wrec)up to 15.0 J·cm^(-3) and energy efficiency of 82.8%are obtained at 1500 kV·cm^(-3) in Sm/Ta co-doped AN multilayer ceramic capacitor(MLCC),which are superior to those of the state-of-the-art AN-based ceramic capacitor.Moreover,the discharge energy density(Wa)in direct-current charge-discharge performance reaches 9.1 J·cm^(-3),which is superior to that of the reported lead-free energy storage systems.The synergistic design of composition and multilayer structure provides an applicable method to optimize the energy storage performance in all dielectric energy storage systems.

Regulating local electric field to optimize the energy storage performance of antiferroelectric ceramics via a composite strategy

Electrostatic energy storage technology based on dielectrics is the basis of advanced electronics and high-power electrical systems.High polarization(P)and high electric breakdown strength(Eb)are the key parameters for dielectric materials to achieve superior energy storage performance.In this work,a composite strategy based on antiferroelectric dielectrics(AFEs)has been proposed to improve the energy storage performance.Here,AlN is selected as the second phase for the(Pb_(0.915)Ba_(0.04)La_(0.03))(Zr_(0.65)Sn_(0.3)Ti_(0.05))O_(3)(PBLZST)AFEs,which is embedded in the grain boundaries to construct insulating networks and regulate the local electric field,improving the Eb.Meanwhile,it is emphasized that AFEs have the AFE–FE and FE–AFE phase transitions,and the increase of the phase transition electric fields can further improve the recoverable energy density(Wrec).As a result,the Eb increases from 180 to 290 kV·cm−1 with a simultaneous increase of the phase transition electric fields,magnifying the Wrec to~144%of the pristine PBLZST.The mechanism for enhanced Eb and the phase transition electric fields is revealed by the finite element simulation method.Moreover,the PBLZST:1.0 wt%AlN composite ceramics exhibit favorable temperature stability,frequency stability,and charge–discharge ability,making the composite ceramics a promising candidate for energy storage applications.

Energy storage properties in Nd-doped AgNbTaO_(3) lead-free antiferroelectric ceramics with Nb-site vacancies

It is crucial to discover lead-free materials with ultrahigh recoverable energy density(Wrec)that can be employed in future pulse power capacitors.In this work,a high Wrec of 4.51 J/cm^(3) was successfully obtained in lead-free Nd-doped AgNb_(0.8)Ta_(0.2)O_(3) antifer­roelectric ceramics at an applied electric field of 290 kV/cm.It is discovered that Nd doping paired with Nb-site vacancies could stabilize the antiferroelectric phase by lowering the temperatures of the M1-M2 and M2-M3 phase transitions,which leads to higher energy storage efficiency.Furthermore,Nd and Ta co-doping will contribute to the electrical homogeneity and low elec­trical conductivity,resulting in large breakdown strengths.Aliovalent doping in Ag-site with Nb-site vacancies serves as a novel strategy for the construction of AgNbO_(3)-based ceramics with excellent energy storage performance.

Correlation between multi-factor phase diagrams and complex electrocaloric behaviors in PNZST antiferroelectric ceramic system

Ferroelectric(FE)phase transition with a large polarization change benefits to generate large electrocaloric(EC)effect for solid-sate and zero-carbon cooling application.However,most EC studies only focus on the single-physical factor associated phase transition.Herein,we initiated a comprehensive discussion on phase transition in Pb_(0.99)Nb_(0.02)[(Zr_(0.6)Sn_(0.4))1−xTix]_(0.98)O_(3)(PNZST100x)antiferroelectric(AFE)ceramic system under the joint action of multi-physical factors,including composition,temperature,and electric field.Due to low energy barrier and enhanced zero-field entropy,the multi-phase coexistence point(x=0.12)in the composition–temperature phase diagram yields a large positive EC peak of maximum temperature change(ΔT_(max))=2.44 K(at 40 kV/cm).Moreover,the electric field–temperature phase diagrams for four representative ceramics provide a more explicit guidance for EC evolution behavior.Besides the positive EC peaks near various phase transition temperatures,giant positive EC effects are also brought out by the electric field-induced phase transition from tetragonal AFE(AFET)to low-temperature rhombohedral FE(FER),which is reflected by a positive-slope boundary in the electric field–temperature phase diagram,while significant negative EC responses are generated by the phase transition from AFET to high-temperature multi-cell cubic paraelectric(PEMCC)with a negative-slope phase boundary.This work emphasizes the importance of phase diagram covering multi-physical factors for high-performance EC material design.

Local probing of the non-uniform distribution of ferrielectric and antiferroelectric phases

Piezoresponse force microscopy(PFM)is an indispensable tool in the investigation of local electromechanical responses and polarization switching.The acquired data provide spatial information on the local disparity of polarization switching and electromechanical responses,making this technique advantageous over macroscopic approaches.Despite its widespread application in ferroelectrics,it has rarely been used to investigate the ferrielectric(FiE)behaviors in antiferroelectric(AFE)materials.Herein,the PFM was utilized to study the local electromechanical behavior and distribution of FiE,and the AFE phases of PbZrO_(3)thin-film were studied,where only the FiE behavior is observable using a macroscopic approach.The FiE region resembles a ferroelectric material at low voltages but exhibits a unique on-field amplitude response at high voltages.In contrast,the AFE region only yields an observable response at high voltages.Phase-field simulations reveal the coexistence of AFE and FiE states as well as the phase-transition processes that underpin our experimental observations.Our work illustrates the usefulness of PFM as an analytical tool to characterize AFE/FiE materials and their phase-coexistence behavior,thereby providing insights to guide property modification and potential applications.

Realizing simultaneously excellent energy storage and discharge properties in AgNbO_(3)based antiferroelectric ceramics via La^(3t)and Ta^(5+)co-substitution strategy

AgNbO_(3)based antiferroelectric(AFE)ceramics have large maximum polarization and low remanent polarization,and thus are important candidates for fabricating dielectric capacitors.However,their energy storage performances have been still large difference with those of lead-based AFEs because of their room-temperature ferrielectric(FIE)behavior.In this study,novel La^(3+)and Ta^(5+)co-substituted AgNbO_(3)ceramics are designed and developed.The introduction of La^(3+)and Ta^(5+)decreases the tolerance factor,reduces the polarizability of B-site cations and increases local structure heterogeneity of AgNbO_(3),which enhance AFE phase stability and refine polarization-electric field(PeE)loops.Besides,adding La^(3+)and Ta^(5+)into AgNbO_(3)ceramics causes the decrease of the grain sizes and the increase of the band gap,which contribute to increased Eb.As a consequence,a high recoverable energy density of 6.79 J/cm3 and large efficiency of 82.1%,which exceed those of many recently reported AgNbO_(3)based ceramics in terms of overall energy storage properties,are obtained in(Ag0.88La0.04)(Nb0.96Ta0.04)O_(3)ceramics.Furthermore,the discharge properties of the ceramic with discharge time of 16 ns and power density of 145.03 MW/cm3 outperform those of many lead-free dielectric ceramics.

Effect of rare-earth doping on the dielectric property and polarization behavior of antiferroelectric sodium niobate-based ceramics

The lead-free 0.96NaNbO_(3)-0.04CaSnO_(3) ceramics with rare-earth dopants(La,Sm and Lu)(NCLn100x)were prepared and characterized.It is found that a certain amount of La substitution stabilizes the antiferroelectric(AFE)phase but alleviates the lattice distortion in the fresh samples.Re-entrant-like characteristics are observed in the temperature e dielectric constant curves with the room temperature P phase gradually replaced by a possible R phase.Relaxor-like hysteresis loops with suppressed hysteresis loss and remanent polarization were obtained at high La content,achieving a relatively high Wre of 2.1 J/cm^(3) at a low electric field(250 kV/cm).The relaxation behaviors of the ferroelectric(FE)domain measured by piezoresponse force microscopy suggest an even long characteristic relaxation time of field-induced FE phase,which is different from the situations of other AFE perovskites.Via an explanatory defected diatomic chain model,we propose that a much larger mass of substitutive ion than the origin one helps to induce low-frequency localized mode,which is believed to be in favor of the formation of polar nano-regions and hence strengthens the dynamic stability of FE phase during electric field loading.Our research provides a further understanding of the tuning strategy for enhancing the antiferroelectricity of the NaNbO_(3)-based system.

Novel lead-free NaNbO_(3) -based relaxor antiferroelectric ceramics with ultrahigh energy storage density and high efficiency

The development of environmentally friendly ceramics for electrostatic energy storage has drawn growing interest due to the wide application in high power and/or pulsed power electronic systems.However,it is difficult to simultaneously achieve ultrahigh recoverable energy storage density(W rec>8 J/cm^(3))and high efficiency(η>80%),which restricts their application in the miniaturized,light weight and easy integrated electronic devices.Herein,the novel NaNbO_(3)-(Bi_(0.8)Sr_(0.2))(Fe_(0.9) Nb_(0.1))O_(3) relaxor antiferro-electric ceramics,which integrates the merits of antiferroelectrics and relaxors,are demonstrated to exhibit stabilized antiferroelectric phase and enhanced dielectric relaxor behavior.Of particular impor-tance is that the 0.88NN-0.12BSFN ceramic achieves giant electric breakdown strength E_(b)=98.3 kV/mm,ultrahigh W _(rec)=16.5 J/cm^(3) and high h=83.3%,as well as excellent frequency,cycling and thermal reliability simultaneously.The comprehensive energy storage performance of NN-BSFN not only out-performs state-of-the-art dielectric ceramics by comparison,but also displays outstanding potential for next-generation energy storage capacitors.