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.

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.

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.

Perspective on antiferroelectrics for energy storage and conversion applications

As a close relative of ferroelectricity,antiferroelectricity has received a recent resurgence of interest driven by technological aspirations in energy-efficient applications,such as energy storage capacitors,solid-state cooling devices,explosive energy conversion,and displacement transducers.Though prolonged efforts in this area have led to certain progress and the discovery of more than 100 antiferroelectric materials over the last 70 years,some scientific and technological issues remain unresolved.Herein,we provide perspectives on the development of antiferroelectrics for energy storage and conversion applications,as well as a comprehensive understanding of the structural origin of antiferroelectricity and field-induced phase transitions,followed by design strategies for new lead-free antiferroelectrics.We also envision unprecedented challenges in the development of promising antiferroelectric materials that bridge materials design and real applications.Future research in these directions will open up new possibilities in resolving the mystery of antiferroelectricity,provide opportunities for comprehending structure-property correlation and developing antiferroelectric/ferroelectric theories,and suggest an approach to the manipulation of phase transitions for real-world applications.

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.

Release of charges under external fields of PbLa(Zr,Sn,Ti)O_3 ceramic

This paper investigates the pyroelectric of poled antiferroelectric （AFE） ceramic Pbo.97Lao.02 （Zro.69Sno.196 Ti0.114）03 and its remnant polarization dependence of hydrostatic pressure. The results show that the bound charges of poled sample can be released in short time by temperature field or pressure field. The released charge abruptly forms a large pulse current. The phenomena of released charge under external fields result in the ferroelectric-AFE phase transition induced by temperature or hydrostatic pressure.

Study of RAINBOW Actuators Made of PSZT

A new type of large\|displacement actuator called RAINBOW (Reduced And Internally Biased Oxide Wafer) was fabricated by a chemical reduction of PSZT antiferroelectric ceramic. It is found that PSZT was easily reduced and the optimal conditions for producing RAINBOW samples were determined to be 870℃ for 2~3 h. The AFE\|FE phase transitions occur at lower field strength in RAINBOWs compared with normal PSZT. Larger axial displacement (about 190μm) was obtained from the RAINBOWs by application of electric ...

Electric properties and phase transition behavior in lead lanthanum zirconate stannate titanate ceramics with low zirconate content

The phase transitions, dielectric properties, and polarization versus electric field （P-E） hysteresis loops of Pbo.97Lao.02（Zr0.42Sn0.58-xTix）O3 （0.13≤ x ≤0.18） （PLZST） bulk ceramics were systematically investigated. This study exhibited a sequence of phase transitions by analyzing the change of the P-E hysteresis loops with increasing temperature. The anfiferroelectric （AFE） to ferroelectric （FE） phase boundary of PLZST with the Zr content of 0.42 was found to locate at the Ti content between 0.14 and 0.15. This work is aimed to improve the ternary phase diagram of lanthanum-doped PZST with the Zr content of 0.42 and will be a good reference for seeking high energy storage density in the PLZST system with low-Zr content.

Geometric and Electronic Structure of Squaric Acid from DFT Calculation

The crystal and electronic structure of antiferroelectric squaric acid is studied using density functional theory method, and the exchange correlation effects are treated by the generalized approximation. In order to understand the ferroelectricity of H2SQ in the molecular plane and the antiferroelectricity in whole crystal, the density of states, charge density distribution and band structure are calculated. The result showed that O2p and C2p play important roles in the interactions between layers. The hybridizations of 02s-Hls and 02p-Hls are responsible for the tendency to ferroelectricity within each layer.

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.

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.

Dielectric Properties and the Phase Transition of Pure and Cerium Doped Calcium-Barium-Niobate

The complex dielectric constant of pure and cerium doped calcium-barium-niobate (CBN) was studied at frequencies 20 Hz ≤ f ≤ 1 MHz in the temperature range 300 K ≤ T ≤ 650 K and compared with the results for the well known ferroelectric relaxor strontium-barium-niobate (SBN). By the analysis of the systematically taken temperature and frequency dependent measurements of the dielectric constant the phase transition characteristic of the investigated materials was evaluated. From the results it must be assumed that CBN shows a slightly diffuse phase transition without relaxor behavior. Doping with cerium yields a definitely different phase transition characteristic with some indications for a relaxor type ferroelectric material, which are common from SBN.

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℃).

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.

Role of polarization evolution in the hysteresis effect of Pb-based antiferroelecrtics

The electric field-induced irreversible domain wall motion results in a ferroelectric(FE) hysteresis. In antiferroelectrics(AFEs), the irreversible phase transition is the main reason for the hysteresis effects, which plays an important role in energy storage performance. Compared to the well-demonstrated FE hysteresis,the structural mechanism of the hysteresis in AFE is not well understood. In this work, the underlying correlation between structure and the hysteresis effect is unveiled in Pb(Zr,Sn,Ti)O_(3) AFE system by using in-situ electrical biasing synchrotron X-ray diffraction. It is found that the AFE with a canting dipole configuration, which shows a continuous polarization rotation under the electric field, tends to have a small hysteresis effect. It presents a negligible phase transition, a small axis ratio, and electric field-induced lattice changing, small domain switching. All these features together lead to a slim hysteresis loop and a high energy storage efficiency. These results offer a deep insight into the structure-hysteresis relationship of AFEs and are helpful for the design of energy storage material.

Combinatorial optimization of perovskite-based ferroelectric ceramics for energy storage applications

With the increasing impacts of climate change and resource depletion,dielectric capacitors,with their exceptional stability,fast charging and discharging rates,and ability to operate under more extreme conditions,are emerging as promising high-demand candidates for high-performance energy storage devices,distinguishing them from traditional electrochemical capacitors and batteries.However,due to the shortcomings of various dielectric ceramics(e.g.,paraelectrics(PEs),ferroelectrics(FEs),and antiferroelectrics(AFEs)),their low polarizability,low breakdown strength(BDS),and large hysteresis loss limit their standalone use in the advancement of energy storage ceramics.Therefore,synthesizing novel perovskite-based materials that exhibit high energy density,high energy efficiency,and low loss is crucial for achieving superior energy storage performance.In this review,we outline the recent development of perovskitebased ferroelectric energy storage ceramics from the perspective of combinatorial optimization for tailoring ferroelectric hysteresis loops and comprehensively discuss the properties arising from the different combinations of components.We also provide future guidelines in this realm.Therefore,the combinatorial optimization strategy in this review will open up a practical route toward the application of new high-performance ferroelectric energy storage devices.

Observation of stabilized negative capacitance effect in hafnium-based ferroic films

A negative capacitance(NC)effect has been proposed as a critical pathway to overcome the‘Boltzmann tyranny’of electrons,achieve the steep slope operation of transistors and reduce the power dissipation of current semiconductor devices.In particular,the ferroic property in hafnium-based films with fluorite structure provides an opportunity for the application of the NC effect in electronic devices.However,to date,only a transient NC effect has been confirmed in hafnium-based ferroic materials,which is usually accompanied by hysteresis and is detrimental to low-power transistor operations.The stabilized NC effect enables hysteresis-free and low-power transistors but is difficult to observe and demonstrate in hafnium-based films.This difficulty is closely related to the polycrystalline and multi-phase structure of hafnium-based films fabricated by atomic layer deposition or chemical solution deposition.Here,we prepare epitaxial ferroelectric Hf_(0.5)Zr_(0.5)O_(2) and antiferroelectric ZrO_(2) films with single-phase structure and observe the capacitance enhancement effect of Hf_(0.5)Zr_(0.5)O_(2)/Al_(2)O_(3) and ZrO_(2)/Al_(2)O_(3) capacitors compared to that of the isolated Al_(2)O_(3) capacitor,verifying the stabilized NC effect.The capacitance of Hf_(0.5)Zr_(0.5)O_(2) and ZrO_(2) is evaluated as−17.41 and−27.64 pF,respectively.The observation of the stabilized NC effect in hafnium-based films sheds light on NC studies and paves the way for low-power transistors.