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.

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.

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.

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.

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.

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.

AgNbO_(3) antiferroelectric film with high energy storage performance

Antiferroelectric materials with double hysteresis loops are attractive for energy storage applications,which are becoming increasingly important for power electronics nowadays.Among them,AgNbO_(3) based lead-free ceramics have attracted intensive interest as one of promising environmental-friendly candidates.However,most of the AgNbO_(3) based ceramics suffers from low dielectric breakdown strength(Eb).The limitation of low Eb is broken to some extent in this work.Here,AgNbO_(3) epitaxial films were fabricated by pulsed laser deposition,which possess high Eb of 624 kV/cm.The(001)AgNbO_(3) epitaxial film reveals typical antiferroelectric hysteresis loops when the applied electric fields are over 300 kV/cm.A recoverable energy density of 5.8 J/cm^(3) and an energy efficiency of 55.8%are obtained at 600 kV/cm,which demonstrates the great promise of the AgNbO_(3) film for energy storage applications.

Phase engineering in NaNbO_(3) antiferroelectrics for high energystorage density

The NaNbO_(3) antiferroelectrics have been considered as a potential candidate for dielectric capacitorsapplications. However, the high-electric-field-unstable antiferroelectric phase resulted in low energystorage density and efficiency. Herein, good energy storage properties were realized in (1-x)NaNbO_(3)- xNaTaO_(3) ceramics, by building a new phase boundary. As a result, a high recoverable energy density(Wrec) of 2.2 J/cm3 and efficiency (h) of 80.1% were achieved in 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic at300 kV/cm. The excellent energy storage performance originates from an antiferroelectric-paraelectricphase boundary with simultaneously high polarization and low hysteresis, by tailoring the ratio ofantiferroelectric and paraelectric phases. Moreover, the 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic also exhibitedgood temperature and frequency stability, together with excellent charge-discharge performance. Theresults pave a good way of designing new NaNbO_(3)-based antiferroelectrics with good energy storageperformance.

Achieving stable relaxor antiferroelectric P phase in NaNbO_(3)-based lead-free ceramics for energy-storage applications

Compared with antiferroelectric(AFE)orthothombic R phases,AFE orthothombic P phases in Na NbO_(3)(NN)ceramics have been rarely investigated,particularly in the field of energy-storage capadtors.The main bottlenedk is closely related to the contradiction between d fficultly achieved stable relaxor AFE P phase and easily induced P-R phase transition during modifying dhemical compositions.Herein,we reporta novel lead-free AFE ceramic of(1-x)NN-x(Bi_(0.5)K_(0.5))ZrO_(3)((1-x)NN-xBKZ)with a pure AFE P phase str ucture,which exhibits excellent energy-storage characteristics,such as an ultrahigh recoverable energy density(W_(rec))-4.4 J/cm^(3) at x=0.11,a large powder density P_(D)-104 MW/cm^(3) and a fast discharge rate t_(0.9)-45 ns.The analysis of polarization-field response,Raman spectrum and transmission elecron microscopy demonstrates that the giant amplification of W_(rec) by≥177% should be ma inly ascribed to the simultaneously and effectively enhanced AFE P phase stbility and its relaxor dharacteristics,resulting in a diffused reversible electric field-induced AFE P-ferroelectric phase transition with concurrently incre.ased driving electric fields.Different from mast(1-x)NN-xABO_(3) systems,it was found that the reduced polarizability of B-site cations dominates the enhanced AFE P-phase stability in(1-x)NN-xBKZ ceramics,but the almost unchanged tolerance factor tends to ause the AFE R phase to be induced at a relatively high x value.

NaNbO_(3) modulated phase transition behavior and antiferroelectric stability evolution in 0.88(Bi_(0.5)Na_(0.5))TiO_(3)-0.12BaTiO_(3) lead-free ceramics

Giant strains in(Bi_(0.5)Na_(0.5))TiO_(3) based ceramics are usually attributed to electric field induced nonpolar to polar phase transition.Whether it is an ergodic relaxor R3c/P4mm ferroelectric(FE)to long-range ordered FE phase transformation or a reversible P4bm antiferroelectric(AFE)to FE phase transition is still unclear.Herein,lead-free(0.88-x)(Bi_(0.5)Na_(0.5))TiO_(3)-0.12BaTiO_(3-x)NaNbO_(3) ceramics exhibit a compositionmodulated FE tetragonal P4mm to relaxor AFE tetragonal P4bm phase transition,in which double hysteresis loop,sprout-shaped S-E curves,near-zero quasi-static d33 together with a large volume change suggest the AFE characteristics of P4bm phase.An interesting finding is that the reversibility of fieldinduced AFE P4bm phase to FE P4mm phase transition strongly depends on the NN content,from being completely irreversible at x=0.01e0.02,to partially reversible at x=0.03e0.05,and finally to completely reversible at x=0.06e0.08.It is indicated that the variation of reversibility should be attributed to the change of relative free energy caused by decreasing the FE to AFE phase transition temperature with increasing the NN content.