The Ginzburg-Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of re...The Ginzburg-Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of relaxor ferro-electrics. With the increase of random field, the dipole configuration evolves from the long-range ferroelectric order into the coexistence of short-range dipole-clusters and less polarized matrix. The dipole-cluster phase above the transition temperature and superparaelectric fluctuations far below this temperature are identified for the relaxor ferroelectrics. We investigate the frequency dispersion and the time-domain spectrum of the dielectric relaxation, demonstrating the Vogel-Fulcher relationship and the multi-peaked time-domain distribution of the dielectric relaxation.展开更多
The dielectric response of complex perovskite relaxor ferrolectrics Pb(Mg1/3Nb2/3) O3 with respect to temperature and frequency was carefully measured. Using a normalized method of the 'universal' many-body t...The dielectric response of complex perovskite relaxor ferrolectrics Pb(Mg1/3Nb2/3) O3 with respect to temperature and frequency was carefully measured. Using a normalized method of the 'universal' many-body theory, the relaxation process was analyzed around the temperature of dielectric absorption maximum. There is no structural phase transition near this temperature and the behavior is closely like that of a polar dipole medium. The functional relationship about frequency and temperature of dielectric pormittivity maximum was also fitted to discuss the dynamic behavior of polar microregion. It is confirmed that a new power exponential Arrhenius relation is better to characterize the relaxation behavior than the Vogel-Fulcher and Debye relations. Based on the polarization theory of polar dipoles, we analyzed the relaxation mechanism of ferroelectric microdomains of relaxor ferroelectrics, and get an ideal distribution function of relaxation time. Consequently, a simulated dielectric response dependence on temperature and frequencies can be expressed, which is well coincided with experiment results.展开更多
Ultrafast charge/discharge process and ultrahigh power density enable dielectrics essential components in modern electrical and electronic devices, especially in pulse power systems. However, in recent years, the ener...Ultrafast charge/discharge process and ultrahigh power density enable dielectrics essential components in modern electrical and electronic devices, especially in pulse power systems. However, in recent years, the energy storage performances of present dielectrics are increasingly unable to satisfy the growing demand for miniaturization and integration, which stimulates further researches on dielectrics with higher energy density and efficiency.Among various inorganic dielectrics, perovskite relaxor ferroelectrics are recognized as promising candidates for energy storage applications, with high permittivity and relatively high efficiency. Here, we focus on recent progress and achievements on optimizing perovskite relaxor ferroelectrics toward better energy storage capability through hierarchical design. The principles and key parameters of dielectric energy storage, together with the definition of majority types of dielectrics, are introduced at first. Strategies within various scales include domain, grain size, orientation, and composite engineering are summarized. The existing challenges are presented and future prospects are proposed in the end, with the background of both academic explorations and industrial applications.展开更多
Dielectric capacitors are independent in advanced electronics and pulse power systems as an energy storage and conversion medium.However,achieving high energy density at a low electric field remains challenging for di...Dielectric capacitors are independent in advanced electronics and pulse power systems as an energy storage and conversion medium.However,achieving high energy density at a low electric field remains challenging for dielectric materials to improve the safety of integrated electronic devices.In this work,the strategy of defect engineering-induced phase competition is proposed to improve the polarization behavior and strengthen dielectric temperature stability of(Bi,Na)TiO_(3)(BNT)-based relaxor ferroelectric,i.e.,Na_(0.325)Sr_(0.245)Ba_(0.105-1.5x)□0.5xBi_(0.325tx)TiO_(3)(NSB_(0.105-1.5x)□0.5xB_(0.325tx)T)ceramics by changing the ratio of Bi^(3+)/Ba^(2+).A high recoverable energy density(Wrec=3.6 J/cm^(3))is achieved at a relatively low electric field of 160 kV/cm for x=0.06 composition together with a high dielectric constant of 3142%±15%in a wide temperature range of 30-386℃,which exceeds other lead-free dielectric ceramics at the same electric field.The results demonstrate that NSB_(0.015)□0.03B_(0.385)T ceramics are desirable for advanced pulsed power capacitors and will push the development of defect-tuned functionality of dielectric ceramics for energy storage applications.展开更多
With the development of advanced electronic memory and the advocacy of environmental friendliness,lead-free relaxor ferroelectric capacitors with slim hysteresis loops have received great attention in high power energ...With the development of advanced electronic memory and the advocacy of environmental friendliness,lead-free relaxor ferroelectric capacitors with slim hysteresis loops have received great attention in high power energy storage applications.However,various emerging defects in Sr_(0.7)Bi_(0.2)TiO_(3)based relaxor ferroelectric films can result in inferior energy storage performance.In this work,Mn doping is utilized to modify the defects caused by the excessive Bi compensation in the Sr_(0.7)Bi_(0.2)TiO_(3)relaxor ferroelectric thin films.Those Mn doped Sr_(0.7)Bi_(0.2)TiO_(3)thin films exhibits significantly improved recoverable energy storage density by more than one order of magnitude with an ultrahigh energy storage density(126 J/cm^(3)).By analyzing the change of the chemical environment and using the scanning transmission electron microscopy,we reveal these improved energy storage performances arises from the formation of defect dipoles of Mn^(2+)at B site with oxygen vacancies,suppressing the volume of oxygen vacancies and titanium vacancies simultaneously,and the slush-like“single domain”structure with fluctuated B-site cation displacements stabilized and confined in a single nano-sized crystal grain.This chemical modification strategy in this work can serve as a regular approach to suppress the defects and improve the energy storage performance in ferroelectric thin films with volatile elements.展开更多
In this review the dielectric properties of relaxor ferroelectrics are discussed and compared withthe properties of normal dielectrics and ferroelectrics. We try to draw a general picture ofdielectric relaxation start...In this review the dielectric properties of relaxor ferroelectrics are discussed and compared withthe properties of normal dielectrics and ferroelectrics. We try to draw a general picture ofdielectric relaxation starting from a textbook review of the underlying concepts and pay attentionto common behavior of relaxors rather than to the features observed in specific materials. We hopethat this general approach is beneficial to those physicists, chemists, material scientists and deviceengineers who deal with relaxors. Based on the analysis of dielectric properties, a comprehensivedefinition of relaxors is proposed: relaxors are defined as ferroelectrics in which the maximum inthe temperature dependence of static susceptibility occurs within the temperature range ofdielectric relaxation, but does not coincide with the temperature of singularity of relaxation timeor soft mode frequency.展开更多
Relaxor ferroelectrics have been extensively studied due to their outstanding dielectric,piezoelectric,energy storage,and electro-optical properties.Although various theories were proposed to elaborate on the relaxati...Relaxor ferroelectrics have been extensively studied due to their outstanding dielectric,piezoelectric,energy storage,and electro-optical properties.Although various theories were proposed to elaborate on the relaxation phenomena,polar nanoregions formed by disruption of the long-range-order structures are considered to play a key role in relaxor ferroelectrics.Generally,relaxor ferro-electrics are formed by aliovalent substitution or isovalent substitution in normal ferroelectrics,or further combinations of solid solutions.Herein,one category of BaTiO_(3)-based relaxor ferroelectrics with abnormal phase transition and polarization mismatch phenomena is focused.Characteristic parameters of such BaTiO_(3)-based relaxor ferroelectrics,including the Curie temperature,polarization,and lattice parameter,show a typical“U”-shaped variation with compositions.The studied BaTiO_(3)-based relaxor ferroelectrics are mostly solid solutions of A-site coupling and B-site coupling ferroelectrics,exhibiting polarization mismatch in certain compositions[e.g.,0.9BaTiO_(3)-0.1BiScO_(3),0.8BaTiO_(3)-0.2Bi(Mg_(1/2)Ti_(1/2)O_(3),0.8BaTiO_(3)-0.2Bi(Mg_(2/3)Nb_(1/3)O_(3),0.5BaTiO_(3)-0.5Pb(Mg_(1/3)Nb_(2/3)O_(3),0.4BaTiO_(3)-0.6Pb(Zn_(1/3)Nb_(2/3)O_(30,etc.].Of particular interest is that excellent electrical properties can be achieved in the studied relaxor ferroelectrics.Therefore,polarization mismatch theory can also provide guidance for the design of new high-performance lead-free relaxor ferroelectrics.展开更多
Next-generation advanced high/pulsed power capacitors urgently require dielectric materials with outstanding energy storage performance.Bi_(0.5)Na_(0.5)TiO_(3)-based lead-free materials exhibit high polarization,but t...Next-generation advanced high/pulsed power capacitors urgently require dielectric materials with outstanding energy storage performance.Bi_(0.5)Na_(0.5)TiO_(3)-based lead-free materials exhibit high polarization,but the high remanent polarization and large polarization hysteresis limit their applications in dielectric capacitors.Herein,high-entropy perovskite relaxor ferroelectrics(Na_(0.2)Bi_(0.2)Ba_(0.2)Sr_(0.2)Ca_(0.2))(Ti1-x%Zrx%)O_(3)are designed by adding multiple ions in the A-site and replacing the B-site Ti^(4+)with a certain amount of Zr^(4+).The newly designed system showed high relaxor feature and slim polarization-electric(P-E)loops.Especially,improved relaxor feature and obviously delayed polarization saturation were found with the increasing of Zr^(4+).Of particular importance is that both high recoverable energy storage density of 6.6 J/cm^(3) and energy efficiency of 93.5%were achieved under 550 kV/cm for the ceramics of x=6,accompanying with excellent frequency stability,appreciable thermal stability,and prosperous discharge property.This work not only provides potential dielectric materials for energy storage applications,but also offers an effective strategy to obtain dielectric ceramics with ultrahigh comprehensive energy storage performance to meet the demanding requirements of advanced energy storage applications.展开更多
An overview is presented on the order-disorder structural transitions and the dielectric mechanism in the complex-perovskite type relaxor ferroelectrics, i.e., the relaxors. Emphasis is put on the theoretical understa...An overview is presented on the order-disorder structural transitions and the dielectric mechanism in the complex-perovskite type relaxor ferroelectrics, i.e., the relaxors. Emphasis is put on the theoretical understanding of the structural transitions, the macroscopic dielectric properties, and the relationship between them. The influences of the composition, the temperature, and the atomic interactions on the order-disorder microstructures can be well understood in the cluster-variation-method calculations. The criterion drawn from theoretical analysis is successful in predicting the order-disorder structure of relaxors. Among various physical models about relaxors, the dipole glassy model that described the dielectric response as the thermally activated flips of the local spontaneous polarization under random interactions is discussed in details. The Monte Carlo simulation results of this model are consistent with the linear and nonlinear experiments of relaxors.展开更多
(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferr...(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferroelectric features,among which the ergodic BNKT-0.02BNN exhibits large repeatable electrostrain value Suni¼0.51%at electric field of 65 kV/cm,with high piezoelectric stain coefficient d33*of 890 pm/V at 45 kV/cm,while the non-ergodic compositions present unrepeatable large strain response.Based on the electric field-composition phase diagram,the repeatability of strain response in ergodic compositions can be attributed to the reversible electric-field-induced phase transition.In addition,the effects of BNN contents on the macroscopic strain properties are explored by analyzing the existing states of the polar regions with corresponding thermal evolutions and electric-field-induced phase transitions.This research is expected to guide the design of lead free relaxor ferroelectric materials with desired electrostrain properties.展开更多
Organic and inorganic relaxor ferroelectrics used for electrocaloric effect(ECE)applications areintroduced.Relaxor ferroelectrics offer several advantages for ECE devices,e.g.,infinite stateswithout applying electric ...Organic and inorganic relaxor ferroelectrics used for electrocaloric effect(ECE)applications areintroduced.Relaxor ferroelectrics offer several advantages for ECE devices,e.g.,infinite stateswithout applying electric field,field-induced large polarization,no-hysteresis ofheating and cooling,small-hysteresis polarization loss,room temperature phase transition,and broad temperaturerange.The ECE in relaxor ferroelectrics under a high electric field can be described using a theorysimilar to that for first-order phase transition materials.Large ECE was observed directly inhigh-energy electron irradiated poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE)68/32 mol%copolymers,P(VDF-TrFE-CFE)(CFE-chlorofluoroethylene)59.2/33.6/7.2 mol%terpolymers,P(vDF-TrFE-CFE)-P(VDF-CTFE)(CTFE-chlorotrifluoroethylene)95/5 wt%terpolymer blended films,and(PbLa)(ZrTi)O_(3)(PLZT)ceramic thin films.ECE reported inPb(Sc_(1/2)Ta_(1/2))O_(3)(PST),Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PMN-PT)thin films is also summarized.Finally,the perspective of ECE devices is llustrated.展开更多
For efficient solid-state refrigeration technologies based on electrocaloric effect(ECE),it is a great challenge of simultaneously obtaining a large adiabatic temperature change(DT)within a wide temperature span(Tspan...For efficient solid-state refrigeration technologies based on electrocaloric effect(ECE),it is a great challenge of simultaneously obtaining a large adiabatic temperature change(DT)within a wide temperature span(Tspan)in lead-free ferroelectric ceramics.Here,we studied the electrocaloric effect(ECE)in(1-x)(Na_(0.5)Bi_(0.5))TiO_(3)-xCaTiO_(3)((1-x)NBT-xCT)and explored the combining effect of morphotropic phase boundary(MPB)and relaxor feature.The addition of CT not only constructs a MPB region with the coexistence of rhombohedral and orthorhombic phases,but also enhances the relaxor feature.The ECE peak appears around the freezing temperature(Tf),and shifts toward to lower temperature with the increasing CT amount.The directly measured ECE result shows that the ceramic of x=0.10,which is in the MPB region,has an optimal ECE property of DTmax=1.28 K@60℃under 60 kV/cm with a wide Tspan of 65C.The enhanced ECE originates from the electric-field-induced transition between more types of polar nanoregions and long-range ferroelectric macrodomains.For the composition with more relaxor feature in the MPB region,such as x?0.12,the ECE is relatively weak under low electric fields but it exhibits a sharp increment under a sufficiently high electric field.This work provides a guideline to develop the solidestate cooling devices for electronic components.展开更多
Dielectric ceramics with ultrahigh power density and ultrafast charge/discharge rates are crucial components of advanced dielectric capacitors. However, enhancing their comprehensive performance remains a major challe...Dielectric ceramics with ultrahigh power density and ultrafast charge/discharge rates are crucial components of advanced dielectric capacitors. However, enhancing their comprehensive performance remains a major challenge for cutting-edge applications. Here, a high-entropy strategy is proposed to construct multiple local distortions, including various types of oxygen octahedral tilts, highly dynamic polar nanoregions, and lattice distortions. This approach effectively delays polarization saturation, reduces energy loss, and, in conjunction with the ultrafine grains induced by the high-entropy effect, enhances mechanical properties and breakdown field. Therefore, a remarkable recoverable energy density of 9.1 J cm-3, a high conversion efficiency of 82.7 %, and a large Vickers hardness of 8.77 GPa are simultaneously achieved in 0.73Bi_(0.47)Na_(0.47)Ba_(0.06)TiO_(3)-0.27Ca_(0.7)La_(0.2)Zr_(0.15)Ti_(0.85)O_(3) lead-free high-entropy relaxors. Additionally, superior frequency and temperature stability, as well as excellent charge/discharge performance, are also obtained. These findings demonstrate that the high-entropy strategy is a promising method for designing high-performance dielectric ceramics.展开更多
Advanced lead-free energy storage ceramics play an indispensable role in next-generation pulse power capacitors market.Here,an ultrahigh energy storage density of~13.8 J cm^(-3)and a large efficiency of~82.4%are achie...Advanced lead-free energy storage ceramics play an indispensable role in next-generation pulse power capacitors market.Here,an ultrahigh energy storage density of~13.8 J cm^(-3)and a large efficiency of~82.4%are achieved in high-entropy lead-free relaxor ferroelectrics by increasing configuration entropy,named high-entropy strategy,realizing nearly ten times growth of energy storage density compared with low-entropy material.Evolution of energy storage performance and domain structure with increasing configuration entropy is systematically revealed for the first time.The achievement of excellent energy storage properties should be attributed to the enhanced random field,decreased nanodomain size,strong multiple local distortions,and improved breakdown field.Furthermore,the excellent frequency and fatigue stability as well as charge/discharge properties with superior thermal stability are also realized.The significantly enhanced comprehensive energy storage performance by increasing configuration entropy demonstrates that high entropy is an effective but convenient strategy to design new high-performance dielectrics,promoting the development of advanced capacitors.展开更多
Inspired by the increasing demand for energy-storage capacitors in electrical and electronic systems, dielectrics with high energy-storage performance have attracted more and more attention. AgNbO_(3) -based lead-free...Inspired by the increasing demand for energy-storage capacitors in electrical and electronic systems, dielectrics with high energy-storage performance have attracted more and more attention. AgNbO_(3) -based lead-free ceramics serve as one of the most promising environmental-friendly candidates. However, their energy storage optimization is seriously limited by the low breakdown strength. Fortunately, thin film as a form of AgNbO3 materials can effectively improve the breakdown strength. In this work, AgNbO_(3)film with ∼550 nm in thickness was deposited on SrRuO_(3 )/(001)SrTiO_(3) using pulsed laser deposition. The AgNbO_(3) film reveals typical relaxor ferroelectric hysteresis loops due to the new nanopillar structure, which contributes to high breakdown strength of up to 1200 kV cm^(-1) . Benefiting from the high breakdown strength, a recoverable energy storage density of 10.3 J cm^(-3) and an energy efficiency of 72.2% are obtained in the AgNbO_(3) film, which demonstrates the promising prospect of AgNbO_(3) film for energy storage applications.展开更多
(Ba_((1-x))Bi_(x))(Ti_((1-x))Mg_(2 x/3)Ta_(x/3))O_(3)(BBTMT-x,x=0.075,0.1,0.125,and 0.15)ceramics were manufactured via a solid-phase reaction method.The pseudo-cubic BaTiO_(3)(BT)as the primary phase and Ba_(4)MgTi_(...(Ba_((1-x))Bi_(x))(Ti_((1-x))Mg_(2 x/3)Ta_(x/3))O_(3)(BBTMT-x,x=0.075,0.1,0.125,and 0.15)ceramics were manufactured via a solid-phase reaction method.The pseudo-cubic BaTiO_(3)(BT)as the primary phase and Ba_(4)MgTi_(11)O_(27)as the secondary phase were detected in BBTMT-x ceramics.The elongated rod-shaped grains therein be-came numerous as x increased.The introduction of Bi/Mg/Ta(BMT)elements transformed BT ceramics from ferroelectrics to relaxor ferroelectrics and induced the formation of short-range order polar nanore-gions(PNRs),which were beneficial for the preeminent energy storage properties(ESPs).The highest ESPs(a giant recoverable energy-storage density W_(rec)of 5.97 J cm^(-3)with a high-efficiencyηof 87.4%)were achieved in BBTMT-0.1 ceramics at 710 kV cm^(-1).BBTMT-0.1 ceramics also possessed excellent fre-quency(1-500 Hz),temperature(30-150℃),and fatigue(cycle number of 1-100,000)stabilities.Finite element simulations(FES)demonstrated that elongated rod-shaped grains had stronger obstacles to the development of electrical branches,which was beneficial to improving the comprehensive ESPs.展开更多
The environmentally-friendly(1-x)Ba(Zr_(1/3)Ti_(2/3))O_(3)-xBaMg_(0.1)Ta_(0.9))O_(3)(x=0,0.02,0.04,0.06,0.08)relaxor ferroelectric ceramics were prepared by the conventional solid-state method and sintered in air at 1...The environmentally-friendly(1-x)Ba(Zr_(1/3)Ti_(2/3))O_(3)-xBaMg_(0.1)Ta_(0.9))O_(3)(x=0,0.02,0.04,0.06,0.08)relaxor ferroelectric ceramics were prepared by the conventional solid-state method and sintered in air at 1400°C for 2 h.SEM and XRD analyses were utilized to study the surface morphologies and the crystalline structures,respectively.The effects of BaMg_(0.1)Ta_(0.9))O_(3)on the phase transformation,dielectric and ferroelectric properties of Ba(Zr_(1/3)Ti_(2/3))O_(3)ceramics were also investigated.It is found that the average grain size of(1-x)Ba(Zr_(1/3)Ti_(2/3))O_(3)-xBaMg_(0.1)Ta_(0.9))O_(3)(BZT-BMT)perovskite single-phase ceramics decreases as the content of BaMg_(0.1)Ta_(0.9))O_(3)(BMT)increases.The relaxor ferroelectric behavior with diffuse phase transition and well-defined frequency dispersion of dielectric maximum temperature is found for the ceramic with increasing x values.0.98BZT-0.02BMT ceramic shows very good dielectric properties with the relative permittivity and the dielectric loss,measured at 100 k Hz as 6034 and 0.01399 respectively at room temperature.Both remnant polarization and coercive field decreased with increasing BMT content,indicating a transition from the ferroelectric phase to the paraelectric phase at room temperature.展开更多
The microstructure,dielectric and ferroelectric properties of(1-y)Ba(Zr0.1Ti0.9)O3-yBa(Zn1/3Nb2/3)O3(y=0-0.05)ceramics prepared by traditional solid state method were investigated by X-ray diffractometer,scanning elec...The microstructure,dielectric and ferroelectric properties of(1-y)Ba(Zr0.1Ti0.9)O3-yBa(Zn1/3Nb2/3)O3(y=0-0.05)ceramics prepared by traditional solid state method were investigated by X-ray diffractometer,scanning electron microscope,electric parameter testing system and ferroelectric tester.It is found that the barium zirconate titanate based ceramics are single-phase perovskites as y increases up to 0.05 and their average grain size decreases with the increase of y.The permittivity maximumεr,max is suppressed from 8948 to 1611 at 1 kHz with increasing y,and the ferroelectric-paraelectric phase transition temperature Tm decreases from 93 to-89℃at 1 kHz as y increases.The composition-induced diffuse phase transition is enhanced with increasingy.The relaxor-like ferroelectric behavior with a strong frequency dispersion of Tm and permittivity at T<Tm accompanied by a strong diffuse phase transition is found for the system with high y value.The remnant polarization decreases with increasing y,while the coercive field decreases remarkably and then increases with the increase of y.展开更多
Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0....Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3BiFeO_(3)-x%Mn(x=0,0.5,1.5,2,3)thin films via sol-gel method.Mn ions of divalent valence combine with oxygen vacancies,forming defect complex,which results in marked decline in leakage current and obvious enhancement in breakdown strength.A high energy storage density~47.6 J cm^(-3)and good efficiency~65.68%are simultaneously achieved in 2%Mn doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor.Moreover,the 2%Mn-doped thin film exhibits excellent thermal stability in wide operating temperature range(35–115℃)and strong fatigue endurance behaviors after 108 cycles.The above results demonstrate that 2%Mn-doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor with superior energy storage performances is a potential candidate for electrostatic energy storage.展开更多
Lead-free dielectric ceramics can be used to make quick charge-discharge capacitor devices due to their high power density.Their use in advanced electronic systems,however,has been hampered by their poor energy storag...Lead-free dielectric ceramics can be used to make quick charge-discharge capacitor devices due to their high power density.Their use in advanced electronic systems,however,has been hampered by their poor energy storage performance(ESP),which includes low energy storage efficiency and recoverable energy storage density(Wrec).In this work,we adopted a combinatorial optimization strategy to improve the ESP in(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based relaxor ferroelectric ceramics.To begin,the Bi-containing complex ions Bi(Mg_(2/3)Nb_(1/3))O_(3)(BMN)were introduced into a BNT-based matrix in order to improve the diffuse phase transition,increase Bi-O bond coupling,avoid macro domain development,and limit polarization response hysteresis.Second,the viscous polymer process was employed to reduce sample thickness and porosity,resulting in an apparent increase in breakdown strength in(1-x)[0.7(Bi_(1/2)Na_(1/2))TiO_(3)]-0.3SrTiO_(3)-xBi(Mg_(2/3)Nb_(1/3))O_(3)(BS-xBMN)ceramics.Finally,in x=0.20 composition,an amazing Wrecof 5.62 J·cm^(-3)and an ultra-high efficiency of 91.4%were simultaneously achieved at a relatively low field of 330 kV·cm^(-1),together with remarkable temperature stability in the temperature range of 30-140℃(3.5 J·cm^(-3)±5%variation).This research presents a new lead-free dielectric material with superior ESP for use in pulsed power capacitors.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.50832002 and 10874035)the National Basic Research Program of China (Grant No.2009CB623303)
文摘The Ginzburg-Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of relaxor ferro-electrics. With the increase of random field, the dipole configuration evolves from the long-range ferroelectric order into the coexistence of short-range dipole-clusters and less polarized matrix. The dipole-cluster phase above the transition temperature and superparaelectric fluctuations far below this temperature are identified for the relaxor ferroelectrics. We investigate the frequency dispersion and the time-domain spectrum of the dielectric relaxation, demonstrating the Vogel-Fulcher relationship and the multi-peaked time-domain distribution of the dielectric relaxation.
文摘The dielectric response of complex perovskite relaxor ferrolectrics Pb(Mg1/3Nb2/3) O3 with respect to temperature and frequency was carefully measured. Using a normalized method of the 'universal' many-body theory, the relaxation process was analyzed around the temperature of dielectric absorption maximum. There is no structural phase transition near this temperature and the behavior is closely like that of a polar dipole medium. The functional relationship about frequency and temperature of dielectric pormittivity maximum was also fitted to discuss the dynamic behavior of polar microregion. It is confirmed that a new power exponential Arrhenius relation is better to characterize the relaxation behavior than the Vogel-Fulcher and Debye relations. Based on the polarization theory of polar dipoles, we analyzed the relaxation mechanism of ferroelectric microdomains of relaxor ferroelectrics, and get an ideal distribution function of relaxation time. Consequently, a simulated dielectric response dependence on temperature and frequencies can be expressed, which is well coincided with experiment results.
基金financially supported by the National Natural Science Foundation of China (No.51788104)。
文摘Ultrafast charge/discharge process and ultrahigh power density enable dielectrics essential components in modern electrical and electronic devices, especially in pulse power systems. However, in recent years, the energy storage performances of present dielectrics are increasingly unable to satisfy the growing demand for miniaturization and integration, which stimulates further researches on dielectrics with higher energy density and efficiency.Among various inorganic dielectrics, perovskite relaxor ferroelectrics are recognized as promising candidates for energy storage applications, with high permittivity and relatively high efficiency. Here, we focus on recent progress and achievements on optimizing perovskite relaxor ferroelectrics toward better energy storage capability through hierarchical design. The principles and key parameters of dielectric energy storage, together with the definition of majority types of dielectrics, are introduced at first. Strategies within various scales include domain, grain size, orientation, and composite engineering are summarized. The existing challenges are presented and future prospects are proposed in the end, with the background of both academic explorations and industrial applications.
基金supported by National Natural Science Foundation of China(52267002)Natural Science Foundation of Jiangxi Province(20212ACB204010)Science&Technology Research Project of Jiangxi Provincial Education Department(GJJ211301).
文摘Dielectric capacitors are independent in advanced electronics and pulse power systems as an energy storage and conversion medium.However,achieving high energy density at a low electric field remains challenging for dielectric materials to improve the safety of integrated electronic devices.In this work,the strategy of defect engineering-induced phase competition is proposed to improve the polarization behavior and strengthen dielectric temperature stability of(Bi,Na)TiO_(3)(BNT)-based relaxor ferroelectric,i.e.,Na_(0.325)Sr_(0.245)Ba_(0.105-1.5x)□0.5xBi_(0.325tx)TiO_(3)(NSB_(0.105-1.5x)□0.5xB_(0.325tx)T)ceramics by changing the ratio of Bi^(3+)/Ba^(2+).A high recoverable energy density(Wrec=3.6 J/cm^(3))is achieved at a relatively low electric field of 160 kV/cm for x=0.06 composition together with a high dielectric constant of 3142%±15%in a wide temperature range of 30-386℃,which exceeds other lead-free dielectric ceramics at the same electric field.The results demonstrate that NSB_(0.015)□0.03B_(0.385)T ceramics are desirable for advanced pulsed power capacitors and will push the development of defect-tuned functionality of dielectric ceramics for energy storage applications.
基金supported National Natural Science Foundation of China(Grant No.51902155).
文摘With the development of advanced electronic memory and the advocacy of environmental friendliness,lead-free relaxor ferroelectric capacitors with slim hysteresis loops have received great attention in high power energy storage applications.However,various emerging defects in Sr_(0.7)Bi_(0.2)TiO_(3)based relaxor ferroelectric films can result in inferior energy storage performance.In this work,Mn doping is utilized to modify the defects caused by the excessive Bi compensation in the Sr_(0.7)Bi_(0.2)TiO_(3)relaxor ferroelectric thin films.Those Mn doped Sr_(0.7)Bi_(0.2)TiO_(3)thin films exhibits significantly improved recoverable energy storage density by more than one order of magnitude with an ultrahigh energy storage density(126 J/cm^(3)).By analyzing the change of the chemical environment and using the scanning transmission electron microscopy,we reveal these improved energy storage performances arises from the formation of defect dipoles of Mn^(2+)at B site with oxygen vacancies,suppressing the volume of oxygen vacancies and titanium vacancies simultaneously,and the slush-like“single domain”structure with fluctuated B-site cation displacements stabilized and confined in a single nano-sized crystal grain.This chemical modification strategy in this work can serve as a regular approach to suppress the defects and improve the energy storage performance in ferroelectric thin films with volatile elements.
文摘In this review the dielectric properties of relaxor ferroelectrics are discussed and compared withthe properties of normal dielectrics and ferroelectrics. We try to draw a general picture ofdielectric relaxation starting from a textbook review of the underlying concepts and pay attentionto common behavior of relaxors rather than to the features observed in specific materials. We hopethat this general approach is beneficial to those physicists, chemists, material scientists and deviceengineers who deal with relaxors. Based on the analysis of dielectric properties, a comprehensivedefinition of relaxors is proposed: relaxors are defined as ferroelectrics in which the maximum inthe temperature dependence of static susceptibility occurs within the temperature range ofdielectric relaxation, but does not coincide with the temperature of singularity of relaxation timeor soft mode frequency.
基金supported by the National Nature Science Foundation of China(Grant Nos.51772239,51761145024)the National Basic Research Program of China(973 Program)under the Grant No.2015CB654602+1 种基金the International Science&Technology Cooperation Program of China(Grant 2015DFA51100)“111”Project(No.B14040),and Shaanxi Province Project(2017ktpt-21,2018TD-024)。
文摘Relaxor ferroelectrics have been extensively studied due to their outstanding dielectric,piezoelectric,energy storage,and electro-optical properties.Although various theories were proposed to elaborate on the relaxation phenomena,polar nanoregions formed by disruption of the long-range-order structures are considered to play a key role in relaxor ferroelectrics.Generally,relaxor ferro-electrics are formed by aliovalent substitution or isovalent substitution in normal ferroelectrics,or further combinations of solid solutions.Herein,one category of BaTiO_(3)-based relaxor ferroelectrics with abnormal phase transition and polarization mismatch phenomena is focused.Characteristic parameters of such BaTiO_(3)-based relaxor ferroelectrics,including the Curie temperature,polarization,and lattice parameter,show a typical“U”-shaped variation with compositions.The studied BaTiO_(3)-based relaxor ferroelectrics are mostly solid solutions of A-site coupling and B-site coupling ferroelectrics,exhibiting polarization mismatch in certain compositions[e.g.,0.9BaTiO_(3)-0.1BiScO_(3),0.8BaTiO_(3)-0.2Bi(Mg_(1/2)Ti_(1/2)O_(3),0.8BaTiO_(3)-0.2Bi(Mg_(2/3)Nb_(1/3)O_(3),0.5BaTiO_(3)-0.5Pb(Mg_(1/3)Nb_(2/3)O_(3),0.4BaTiO_(3)-0.6Pb(Zn_(1/3)Nb_(2/3)O_(30,etc.].Of particular interest is that excellent electrical properties can be achieved in the studied relaxor ferroelectrics.Therefore,polarization mismatch theory can also provide guidance for the design of new high-performance lead-free relaxor ferroelectrics.
基金This work was financially supported by the Guangxi Natural Science Fund for Distinguished Young Scholars(Grant No.2022GXNSFFA035034)National Natural Science Foundation of China(Grant Nos.52072080 and U22A20127)National Key R&D Program of China(Grant No.2022YFC2408600).We also would like to acknowledge the support from Xiaomi Foundation/Xiaomi Young Talents Program.
文摘Next-generation advanced high/pulsed power capacitors urgently require dielectric materials with outstanding energy storage performance.Bi_(0.5)Na_(0.5)TiO_(3)-based lead-free materials exhibit high polarization,but the high remanent polarization and large polarization hysteresis limit their applications in dielectric capacitors.Herein,high-entropy perovskite relaxor ferroelectrics(Na_(0.2)Bi_(0.2)Ba_(0.2)Sr_(0.2)Ca_(0.2))(Ti1-x%Zrx%)O_(3)are designed by adding multiple ions in the A-site and replacing the B-site Ti^(4+)with a certain amount of Zr^(4+).The newly designed system showed high relaxor feature and slim polarization-electric(P-E)loops.Especially,improved relaxor feature and obviously delayed polarization saturation were found with the increasing of Zr^(4+).Of particular importance is that both high recoverable energy storage density of 6.6 J/cm^(3) and energy efficiency of 93.5%were achieved under 550 kV/cm for the ceramics of x=6,accompanying with excellent frequency stability,appreciable thermal stability,and prosperous discharge property.This work not only provides potential dielectric materials for energy storage applications,but also offers an effective strategy to obtain dielectric ceramics with ultrahigh comprehensive energy storage performance to meet the demanding requirements of advanced energy storage applications.
基金State Key Program of Basic ResearchDevelopm ent! (No.G2 0 0 0 0 6 710 8) the NationalNatural Science Foundation of Chin
文摘An overview is presented on the order-disorder structural transitions and the dielectric mechanism in the complex-perovskite type relaxor ferroelectrics, i.e., the relaxors. Emphasis is put on the theoretical understanding of the structural transitions, the macroscopic dielectric properties, and the relationship between them. The influences of the composition, the temperature, and the atomic interactions on the order-disorder microstructures can be well understood in the cluster-variation-method calculations. The criterion drawn from theoretical analysis is successful in predicting the order-disorder structure of relaxors. Among various physical models about relaxors, the dipole glassy model that described the dielectric response as the thermally activated flips of the local spontaneous polarization under random interactions is discussed in details. The Monte Carlo simulation results of this model are consistent with the linear and nonlinear experiments of relaxors.
基金supported by the National Natural Science Foundation of China(51672220,51902258,51972265)Fundamental Research Funds for the Central Universities(3102019GHXM002)+2 种基金State Key Laboratory of Solidification Processing Project(2019-TZ-04)of China,China Postdoctoral Science Foundation(2019M653729)Natural Science Foundation of Shaanxi Province(2019JQ-621)the Shaanxi Province Postdoctoral Science Foundation(2017BSHEDZZ07).
文摘(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferroelectric features,among which the ergodic BNKT-0.02BNN exhibits large repeatable electrostrain value Suni¼0.51%at electric field of 65 kV/cm,with high piezoelectric stain coefficient d33*of 890 pm/V at 45 kV/cm,while the non-ergodic compositions present unrepeatable large strain response.Based on the electric field-composition phase diagram,the repeatability of strain response in ergodic compositions can be attributed to the reversible electric-field-induced phase transition.In addition,the effects of BNN contents on the macroscopic strain properties are explored by analyzing the existing states of the polar regions with corresponding thermal evolutions and electric-field-induced phase transitions.This research is expected to guide the design of lead free relaxor ferroelectric materials with desired electrostrain properties.
基金the US DoE,Office of Basic Energy Sciences,Division of Materials Science and Engineering under Award No.DE-FG02-07ER46410.
文摘Organic and inorganic relaxor ferroelectrics used for electrocaloric effect(ECE)applications areintroduced.Relaxor ferroelectrics offer several advantages for ECE devices,e.g.,infinite stateswithout applying electric field,field-induced large polarization,no-hysteresis ofheating and cooling,small-hysteresis polarization loss,room temperature phase transition,and broad temperaturerange.The ECE in relaxor ferroelectrics under a high electric field can be described using a theorysimilar to that for first-order phase transition materials.Large ECE was observed directly inhigh-energy electron irradiated poly(vinylidene fluoride-trifluoroethylene)(P(VDF-TrFE)68/32 mol%copolymers,P(VDF-TrFE-CFE)(CFE-chlorofluoroethylene)59.2/33.6/7.2 mol%terpolymers,P(vDF-TrFE-CFE)-P(VDF-CTFE)(CTFE-chlorotrifluoroethylene)95/5 wt%terpolymer blended films,and(PbLa)(ZrTi)O_(3)(PLZT)ceramic thin films.ECE reported inPb(Sc_(1/2)Ta_(1/2))O_(3)(PST),Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PMN-PT)thin films is also summarized.Finally,the perspective of ECE devices is llustrated.
基金supported by grants from National Natural Science Foundation of China(52173217)and 111 project(B170003).
文摘For efficient solid-state refrigeration technologies based on electrocaloric effect(ECE),it is a great challenge of simultaneously obtaining a large adiabatic temperature change(DT)within a wide temperature span(Tspan)in lead-free ferroelectric ceramics.Here,we studied the electrocaloric effect(ECE)in(1-x)(Na_(0.5)Bi_(0.5))TiO_(3)-xCaTiO_(3)((1-x)NBT-xCT)and explored the combining effect of morphotropic phase boundary(MPB)and relaxor feature.The addition of CT not only constructs a MPB region with the coexistence of rhombohedral and orthorhombic phases,but also enhances the relaxor feature.The ECE peak appears around the freezing temperature(Tf),and shifts toward to lower temperature with the increasing CT amount.The directly measured ECE result shows that the ceramic of x=0.10,which is in the MPB region,has an optimal ECE property of DTmax=1.28 K@60℃under 60 kV/cm with a wide Tspan of 65C.The enhanced ECE originates from the electric-field-induced transition between more types of polar nanoregions and long-range ferroelectric macrodomains.For the composition with more relaxor feature in the MPB region,such as x?0.12,the ECE is relatively weak under low electric fields but it exhibits a sharp increment under a sufficiently high electric field.This work provides a guideline to develop the solidestate cooling devices for electronic components.
基金supported by the National Natural Science Foundation of China(No.52102129)the Hunan Provin-cial Natural Science Foundation of China(No.2023JJ30138)the Science and Technology Innovation Program of Hunan Province(2023RC3094).
文摘Dielectric ceramics with ultrahigh power density and ultrafast charge/discharge rates are crucial components of advanced dielectric capacitors. However, enhancing their comprehensive performance remains a major challenge for cutting-edge applications. Here, a high-entropy strategy is proposed to construct multiple local distortions, including various types of oxygen octahedral tilts, highly dynamic polar nanoregions, and lattice distortions. This approach effectively delays polarization saturation, reduces energy loss, and, in conjunction with the ultrafine grains induced by the high-entropy effect, enhances mechanical properties and breakdown field. Therefore, a remarkable recoverable energy density of 9.1 J cm-3, a high conversion efficiency of 82.7 %, and a large Vickers hardness of 8.77 GPa are simultaneously achieved in 0.73Bi_(0.47)Na_(0.47)Ba_(0.06)TiO_(3)-0.27Ca_(0.7)La_(0.2)Zr_(0.15)Ti_(0.85)O_(3) lead-free high-entropy relaxors. Additionally, superior frequency and temperature stability, as well as excellent charge/discharge performance, are also obtained. These findings demonstrate that the high-entropy strategy is a promising method for designing high-performance dielectric ceramics.
基金supported by the National Natural Science Foundation of China(Grant Nos.21825102,22235002,52172181,and 22105017)Key R&D Plan of the Ministry of Science and Technology of China(Grant No.2022YFB3204000)。
文摘Advanced lead-free energy storage ceramics play an indispensable role in next-generation pulse power capacitors market.Here,an ultrahigh energy storage density of~13.8 J cm^(-3)and a large efficiency of~82.4%are achieved in high-entropy lead-free relaxor ferroelectrics by increasing configuration entropy,named high-entropy strategy,realizing nearly ten times growth of energy storage density compared with low-entropy material.Evolution of energy storage performance and domain structure with increasing configuration entropy is systematically revealed for the first time.The achievement of excellent energy storage properties should be attributed to the enhanced random field,decreased nanodomain size,strong multiple local distortions,and improved breakdown field.Furthermore,the excellent frequency and fatigue stability as well as charge/discharge properties with superior thermal stability are also realized.The significantly enhanced comprehensive energy storage performance by increasing configuration entropy demonstrates that high entropy is an effective but convenient strategy to design new high-performance dielectrics,promoting the development of advanced capacitors.
基金supported by the Natural Science Foundation of Hebei Province,China(No.E2021201044)the National Natural Science Foundation of China(Nos.51802068 and 52073144)+3 种基金the Natural Science Foundation of Jiangsu Province,China(No.BK20201301)State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KF202114)the Research Fund of State Key Laboratory of Mechanics and Control of Mechani-cal Structures(Nanjing University of Aeronautics and Astronautics)(No.MCMS-I-0522G02)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘Inspired by the increasing demand for energy-storage capacitors in electrical and electronic systems, dielectrics with high energy-storage performance have attracted more and more attention. AgNbO_(3) -based lead-free ceramics serve as one of the most promising environmental-friendly candidates. However, their energy storage optimization is seriously limited by the low breakdown strength. Fortunately, thin film as a form of AgNbO3 materials can effectively improve the breakdown strength. In this work, AgNbO_(3)film with ∼550 nm in thickness was deposited on SrRuO_(3 )/(001)SrTiO_(3) using pulsed laser deposition. The AgNbO_(3) film reveals typical relaxor ferroelectric hysteresis loops due to the new nanopillar structure, which contributes to high breakdown strength of up to 1200 kV cm^(-1) . Benefiting from the high breakdown strength, a recoverable energy storage density of 10.3 J cm^(-3) and an energy efficiency of 72.2% are obtained in the AgNbO_(3) film, which demonstrates the promising prospect of AgNbO_(3) film for energy storage applications.
基金supported by the Natural Science Foundation of Shandong Province of China(Nos.ZR2020ME035,ZR2020QE043,and ZR2020QE044)National Natural Science Foundation of China(Nos.51872166,52102132,and 52177020)+1 种基金Postdoctoral Science Foundation of China(No.2017M622196)Opening Project of Key Laboratory of Inorganic Functional Materials and Devices,Chinese Academy of Sciences(No.KLIFMD201705).
文摘(Ba_((1-x))Bi_(x))(Ti_((1-x))Mg_(2 x/3)Ta_(x/3))O_(3)(BBTMT-x,x=0.075,0.1,0.125,and 0.15)ceramics were manufactured via a solid-phase reaction method.The pseudo-cubic BaTiO_(3)(BT)as the primary phase and Ba_(4)MgTi_(11)O_(27)as the secondary phase were detected in BBTMT-x ceramics.The elongated rod-shaped grains therein be-came numerous as x increased.The introduction of Bi/Mg/Ta(BMT)elements transformed BT ceramics from ferroelectrics to relaxor ferroelectrics and induced the formation of short-range order polar nanore-gions(PNRs),which were beneficial for the preeminent energy storage properties(ESPs).The highest ESPs(a giant recoverable energy-storage density W_(rec)of 5.97 J cm^(-3)with a high-efficiencyηof 87.4%)were achieved in BBTMT-0.1 ceramics at 710 kV cm^(-1).BBTMT-0.1 ceramics also possessed excellent fre-quency(1-500 Hz),temperature(30-150℃),and fatigue(cycle number of 1-100,000)stabilities.Finite element simulations(FES)demonstrated that elongated rod-shaped grains had stronger obstacles to the development of electrical branches,which was beneficial to improving the comprehensive ESPs.
基金fully sponsored by the National Demonstration Center for Experimental Materials Science and Engineering Education(Jiangsu University of Science and Technology,China)funded by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions,China。
文摘The environmentally-friendly(1-x)Ba(Zr_(1/3)Ti_(2/3))O_(3)-xBaMg_(0.1)Ta_(0.9))O_(3)(x=0,0.02,0.04,0.06,0.08)relaxor ferroelectric ceramics were prepared by the conventional solid-state method and sintered in air at 1400°C for 2 h.SEM and XRD analyses were utilized to study the surface morphologies and the crystalline structures,respectively.The effects of BaMg_(0.1)Ta_(0.9))O_(3)on the phase transformation,dielectric and ferroelectric properties of Ba(Zr_(1/3)Ti_(2/3))O_(3)ceramics were also investigated.It is found that the average grain size of(1-x)Ba(Zr_(1/3)Ti_(2/3))O_(3)-xBaMg_(0.1)Ta_(0.9))O_(3)(BZT-BMT)perovskite single-phase ceramics decreases as the content of BaMg_(0.1)Ta_(0.9))O_(3)(BMT)increases.The relaxor ferroelectric behavior with diffuse phase transition and well-defined frequency dispersion of dielectric maximum temperature is found for the ceramic with increasing x values.0.98BZT-0.02BMT ceramic shows very good dielectric properties with the relative permittivity and the dielectric loss,measured at 100 k Hz as 6034 and 0.01399 respectively at room temperature.Both remnant polarization and coercive field decreased with increasing BMT content,indicating a transition from the ferroelectric phase to the paraelectric phase at room temperature.
基金sponsored by the National Demonstration Center for Experimental Materials Science and Engineering Education (Jiangsu University of Science and Technology, China)the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions, China
文摘The microstructure,dielectric and ferroelectric properties of(1-y)Ba(Zr0.1Ti0.9)O3-yBa(Zn1/3Nb2/3)O3(y=0-0.05)ceramics prepared by traditional solid state method were investigated by X-ray diffractometer,scanning electron microscope,electric parameter testing system and ferroelectric tester.It is found that the barium zirconate titanate based ceramics are single-phase perovskites as y increases up to 0.05 and their average grain size decreases with the increase of y.The permittivity maximumεr,max is suppressed from 8948 to 1611 at 1 kHz with increasing y,and the ferroelectric-paraelectric phase transition temperature Tm decreases from 93 to-89℃at 1 kHz as y increases.The composition-induced diffuse phase transition is enhanced with increasingy.The relaxor-like ferroelectric behavior with a strong frequency dispersion of Tm and permittivity at T<Tm accompanied by a strong diffuse phase transition is found for the system with high y value.The remnant polarization decreases with increasing y,while the coercive field decreases remarkably and then increases with the increase of y.
基金the National Natural Science Foundation of China under Grant No.51332003 and 51372171。
文摘Thin film capacitors with excellent energy storage performances,thermal stability and fatigue endurance are strongly desired in modern electrical and electronic industry.Herein,we design and prepare lead-free0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3BiFeO_(3)-x%Mn(x=0,0.5,1.5,2,3)thin films via sol-gel method.Mn ions of divalent valence combine with oxygen vacancies,forming defect complex,which results in marked decline in leakage current and obvious enhancement in breakdown strength.A high energy storage density~47.6 J cm^(-3)and good efficiency~65.68%are simultaneously achieved in 2%Mn doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor.Moreover,the 2%Mn-doped thin film exhibits excellent thermal stability in wide operating temperature range(35–115℃)and strong fatigue endurance behaviors after 108 cycles.The above results demonstrate that 2%Mn-doped 0.7Sr_(0.7)Bi_(0.2)TiO_(3)-0.3 BiFeO_(3)thin film capacitor with superior energy storage performances is a potential candidate for electrostatic energy storage.
基金financially supported by the National Natural Science Foundation of China(No.52172127)the International Cooperation Project of Shaanxi Province+4 种基金China(No.2022KWZ-22)the National Key Research and Development Program of China(Nos.2021YFE0115000,2021YFB3800602)the Fundamental Research Funds for the Central Universities(No.XJTU)the Natural Science Basis Research Plan in Shaanxi Province of China(No.2020JM-635)the Youth Innovation Team of Shaanxi Universities and Scientific Research Program Funded by Shaanxi Provincial Education Department(No.21JK0869)。
文摘Lead-free dielectric ceramics can be used to make quick charge-discharge capacitor devices due to their high power density.Their use in advanced electronic systems,however,has been hampered by their poor energy storage performance(ESP),which includes low energy storage efficiency and recoverable energy storage density(Wrec).In this work,we adopted a combinatorial optimization strategy to improve the ESP in(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based relaxor ferroelectric ceramics.To begin,the Bi-containing complex ions Bi(Mg_(2/3)Nb_(1/3))O_(3)(BMN)were introduced into a BNT-based matrix in order to improve the diffuse phase transition,increase Bi-O bond coupling,avoid macro domain development,and limit polarization response hysteresis.Second,the viscous polymer process was employed to reduce sample thickness and porosity,resulting in an apparent increase in breakdown strength in(1-x)[0.7(Bi_(1/2)Na_(1/2))TiO_(3)]-0.3SrTiO_(3)-xBi(Mg_(2/3)Nb_(1/3))O_(3)(BS-xBMN)ceramics.Finally,in x=0.20 composition,an amazing Wrecof 5.62 J·cm^(-3)and an ultra-high efficiency of 91.4%were simultaneously achieved at a relatively low field of 330 kV·cm^(-1),together with remarkable temperature stability in the temperature range of 30-140℃(3.5 J·cm^(-3)±5%variation).This research presents a new lead-free dielectric material with superior ESP for use in pulsed power capacitors.
