Giant strains of 0.70% achieved via a field-induced multiple phase transition in BNT-based relaxor antiferroelectric ceramics

Bismuth sodium titanate (BNT)-based lead-free ceramics have attracted a great deal of attention due to their large electrostrains. In this work, a remarkably symmetric strain of 0.7% together with excellent temperature (0.5–0.7% from 25 to 100 °C)/frequency (ΔS<4% from 1 to 20 Hz) stability was observed in the 0.91(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃-0.03NaNbO₃ (BNT-6BT-3NN) AFE P4bm ceramic through constructing R3c/P4mm/P4bm triple-phase coexistence phase boundary. Compared with other two compositions near double-phase coexistence ferroelectric (FE)-antiferroelectric (AFE) phase boundaries, the BNT-6BT-3NN ceramic exhibits a unique field-induced multiple phase transition from the initial AFE P4bm phase to the metastable FE P4mm phase and finally into the FE R3c phase. In-situ structural analysis evidenced a significantly enhanced lattice strain but a comparable strain value from domain switching in BNT-6BT-3NN compared with other compositions. The present study provides a novel strategy for designing high-performance large-strain ceramics in BNT-based relaxor AFE systems.     

Structure variation and energy storage properties of acceptor-modified PBLZST antiferroelectric ceramics

Energy storage capacitors with high recoverable energy density and efficiency are greatly desired in pulse power system. In this study, the energy density and efficiency were enhanced in Mn-modified (Pb_0.93Ba_0.04La_0.02)(Zr_0.65Sn_0.3Ti_0.05)O₃ antiferroelectric ceramics via a conventional solid-state reaction process. The improvement was attributed to the change in the antiferroelectric-to-ferroelectric phase transition electric field (E_F) and the ferroelectric-to-antiferroelectric phase transition electric field (E_A) with a small Mn addition. Mn ions as acceptors, which gave rise to the structure variation, significantly influenced the microstructures, dielectric properties and energy storage performance of the antiferroelectric ceramics. A maximum recoverable energy density of 2.64 J/cm³ with an efficiency of 73% was achieved when x = 0.005, which was 40% higher than that (1.84 J/cm³, 68%) of the pure ceramic counterparts. The results demonstrate that the acceptor modification is an effective way to improve the energy storage density and efficiency of antiferroelectric ceramics by inducing a structure variation and the (Pb_0.93Ba_0.04La_0.02)(Zr_0.65Sn_0.3Ti_0.05)O₃-xMn₂O₃ antiferroelectric ceramics are a promising energy storage material with high-power density.     

Electric field tunable thermal stability of energy storage properties of PLZST antiferroelectric ceramics

The electrical hysteresis behaviors and energy storage performance of Pb_0.97La_0.02(Zr_0.58Sn_0.335Ti_0.085)O₃ antiferroelectric (AFE) ceramics were studied under the combined effects of electric field and temperature. It was observed that the temperature dependence of recoverable energy density (W_re) of AFE ceramics depends critically on the applied electric field. While W_re at lower electric fields (<8 kV/mm) shows increasing tendency with increasing temperature from 20°C to 100°C, W_re at higher electric fields (>8 kV/mm) demonstrates decreasing dependence. There exists an appropriate electric field (8 kV/mm) under which the AFE ceramics exhibit nearly temperature‐independent W_re (the variation is less than 0.5% per 10°C). The underlying physical principles were also discussed in this study. These results indicate that the temperature dependence of W_re of AFE materials can be tuned through selecting appropriate electric fields and provide an avenue to obtain thermal stable energy storage capacitors, which should be of great interest to modern energy storage community.     

Systematical investigation on energy-storage behavior of PLZST antiferroelectric ceramics by composition optimizing

Featured with high polarization and large electric field-induced phase transition, PbZrO₃-based antiferroelectric (AFE) materials are regarded as prospective candidates for energy-storage applications. However, systematical studies on PbZrO₃-based materials are insufficient because of their complex chemical compositions and various phase structures. In this work, (Pb_0.94La_0.04)(Zr_1-x-ySn_xTi_y)O₃ (abbreviated as PLZST, 0 ≤ x ≤ 0.5, 0.01 ≤ y ≤ 0.1) AFE system was selected and the energy-storage behavior was regulated. It is found that low Ti content benefits to obtain satisfactory electric breakdown strength, realizing high energy-storage density. With Sn content increasing, the electric hysteresis decreases gradually, which is beneficial to improve energy conversion efficiency. As a result, a large recoverable energy-storage density of 9.6 J/cm³ and a high energy conversion efficiency of 90.2% were achieved in (Pb_0.94La_0.04)(Zr_0.49Sn_0.5Ti_0.01)O₃ ceramic. This work reveals energy-storage behavior of PLZST AFE materials systematically, providing reference for performance tailoring and new material designing in energy-storage applications.     

Frequency dependence of antiferroelectricferroelectric phase transition of PLZST ceramic

Antiferroelectric (AFE) ceramics are promising for applications in high-power density capacitors, transducers, etc. The forward switching field and backward switching field are critical performance indicators for AFE ceramics, and the coupling between the structure transition and domain orientation makes them different from the coercive field of ferroelectric (FE). Moreover, in practical applications, AFE ceramics are often required to operate at varying frequencies. However, systematic studies regarding the frequency dependence of and are insufficient. In this work, (PLZST) AFE ceramic was fabricated, and two empirical formulas (, ) were proposed to predict the frequency dependence of and . The formulas are based on the electric field–induced phase transition characteristics of AFE and the Kolmogorov–Avrami–Ishibashi domain nucleation-switching model. Furthermore, the dynamic hysteresis loops of PLZST at various frequencies (1–1000 Hz) and temperatures (–) were investigated. The results show that the electric field–induced phase transition of AFE ceramic is dominated by the coupling between the structural transition and domain orientation. The domain orientation hinders the structure transition, leading to an increase in and a decrease in as the frequency of applied electric field increases. Meanwhile, the domain growth process is affected by the structure of AFE, and the value of (domain growth dimensionality) increases with the stability of the AFE structure. For comparison, (PLBZST) relaxor FE ceramic was fabricated. Due to the high mobility of the microdomain, the dynamic hysteresis loop of PLBZST ceramic exhibits excellent frequency stability. The charge–discharge experiment with an ultrahigh equivalent frequency (100 kHz) was performed to investigate the frequency stability of energy release of PLZST and PLBZST. The results may provide guidance for research pertaining to ceramic capacitors with high-power density and high-frequency stability.     

Relaxor antiferroelectric ceramics with ultrahigh efficiency for energy storage applications

Enhancing the efficiency in energy storage capacitors minimizes energy dissipation and improves device durability. A new efficiency-enhancement strategy for antiferroelectric ceramics, imposing relaxor characteristics through forming solid solutions with relaxor compounds, is demonstrated in the present work. Using the classic antiferroelectric (Pb_0.97La_0.02)(Zr_1-x-_ySn_xTi_y)O₃ as model base compositions, Bi(Zn_2/3Nb_1/3)O₃ is found to be most effective in producing the “relaxor antiferroelectric” behavior and minimizing the electric hysteresis. Specifically, a remarkable energy storage efficiency of 95.6% (with an energy density of 2.19 J/cm³ at 115 kV/cm) is achieved in the solid solution 0.90(Pb_0.97La_0.02)(Zr_0.65Sn_0.30Ti_0.05)O₃–0.10Bi(Zn_2/3Nb_1/3)O₃. The validated new strategy, hence, can guide the design of future relaxor antiferroelectric dielectrics for next generation energy storage capacitors.     

Excellent energy storage performance in La and Ta co-doped AgNbO3 antiferroelectric ceramics

Lead-free dielectric materials with high breakdown electric field strength and energy density are required for pulsed power devices with high level of integration. This work describes: (Ag_0.94La_0.02)(Nb_1-xTa_x)O₃ lead-free antiferroelectric ceramics, which were prepared by rolling process. Following composition engineering, an outstanding energy density of 6.9 J cm^-3 at electric field of 490 kV cm^-1 was achieved, coupled with remarkable frequency stability (<1% over 1-100 Hz under E = 420 kV cm^-1) for (Ag_0.94La_0.02)(Nb_0.80Ta_0.20)O₃ ceramics. Moreover, it also shows excellent charge-discharge properties (discharge density = 1429 A cm^-2, power density = 144 MW cm^-3). The addition of La³⁺ and Ta⁵⁺ induced a disordered local structure, which gradually decreased the phase transition temperature of M₂-M₃ to room temperature, reflecting the enhanced antiferroelectricity. All advantageous properties observed for the La and Ta co-doped AgNbO₃ ceramics highlight their significant potential for energy storage applications.     

NaNbO3-based short-range antiferroelectric ceramics with ultrahigh energy storage performance

Lead-free NaNbO₃ (NN) antiferroelectric ceramics provide superior energy storage performance and good temperature/frequency stability, which are solid candidates for dielectric capacitors in high power/pulse electronic power systems. However, their conversion of the antiferroelectric P phase to the ferroelectric Q phase at room temperature is always accompanied with large remnant polarization (P_r), which significantly reduces their effective energy storage density and efficiency. In this study, to optimize the energy storage properties, short-range antiferroelectric (0.95-x)NaNbO₃-xBi(Mg_2/3Nb_1/3)O₃-0.05CaZrO₃ (xBMN) ceramics were designed to stabilize the antiferroelectric phase, in which the local random fields were simultaneously constructed. The results showed that the antiferroelectric orthorhombic P phase was transformed into the R phase, and the local short-range random fields were generated, which effectively inhibited the hysteresis loss and P_r. Of great interest is that the 0.12BMN ceramics displayed a large recoverable energy storage density (W_rec) of 5.9 J/cm³ and high efficiency (η) of 85% at the breakdown strength (E_b) of 640 kV/cm. The material also showed good frequency stability in the frequency range of 2–300 Hz, excellent temperature stability in the temperature range of 20–110 ℃, and a very short discharge time (t_0.9∼4.92 μs). These results indicate that xBMN ceramics have great potential for advanced energy storage capacitor applications.     

Enhanced energy storage density in Ca and Ta co-doped AgNbO3 antiferroelectric ceramics

Ca and Ta co-doped AgNbO₃ antiferroelectric lead-free ceramics were fabricated by rolling process technique, and improved energy storage properties were obtained. X-ray diffraction and Raman spectra indicate a single perovskite structure for (Ag_1-2xCa_x)(Nb_1-xTa_x)O₃ ceramics. The dielectric performances were also investigated, showing that increasing the content of Ca and Ta from 0.1 to 5 mol% gradually decreased the temperatures of the phase transition of monoclinic M₁-M₂ and M₂-M₃. This proved the enhanced antiferroelectricity stability associated with the enlarged low temperature phase transition region. The obtained (Ag_0.90Ca_0.05)(Nb_0.95Ta_0.05)O₃ ceramics exhibit an enhanced recoverable energy storage density (3.36 J/cm³) and efficiency (58.3%) with good temperature and frequency stability. The same composition shows excellent charge and discharge properties with a discharge current as high as 91.5 A and fast discharge speed (150 ns discharge period). All these merits demonstrate that AgNbO₃-based antiferroelectric ceramics are competitive with other lead-based and lead-free dielectric capacitors, which are promising candidates for dielectric energy storage applications.     

高分子固-固相变储能材料的研究与应用

综述了各类高分子固-固相变储能材料的性能、储能机理及其优缺点,介绍了此类材料的各种应用, 并对其发展前景做了探讨和展望。高分子固-固相变储能材料具有储能密度大,相变温度恒定,体积变化小,相变过程无液体泄漏等诸多优点,已成为能源开发利用和材料科学研究的新热点。     

Li+ and Sm3+ co-doped AgNbO3-based antiferroelectric ceramics for high-power energy storage

Ag_1-x-3yLi_xSm_yNbO₃ (x≤0.05, y≤0.05) (ALSN) antiferroelectric ceramics were successfully prepared via conventional solid-state reaction and sinter routes in oxygen atmosphere for improving the energy storage characteristic of pure AgNbO₃. The results indicate that all of the studied compositions display a pure orthorhombic antiferroelectric (AFE) perovskite structure, while their key parameters of electric-field-induced antiferroelectric-ferroelectric transition can be affected by Li⁺ or/and Sm³⁺ doping contents. The Sm³⁺ doping can enhance the stability of antiferroelectric state, giving rise to higher antiferroelectric-ferroelectric transition electric-field (E_F and E_B), while Li⁺ doping can reduce E_F and E_B for Sm³⁺ doped AgNbO₃ with low Sm³⁺ content (y≤0.03). When co-doping the same amounts of Li⁺ and Sm³⁺ at x=y≤0.03, both E_F and E_B almost remain unchanged. At x=y=0.05, the diffuse phase transition (DPT) behavior of antiferroelectric-paraelectric (AFE-PE) phase transition occurred, resulting in a “slim-like” double-polarization hysteresis with significantly enhanced E_F. Due to these features, both W_rec and η are improved compared with pure AgNbO₃. The W_rec and η with composition at x=y=0.05 is 2.33 J/cm³ and 58% under applying electric field of 240 kV/cm, respectively. The results suggest that building DPT behavior of AFE-PE phase transition could be an alternative strategy to improve the energy storage characteristic of AgNbO₃.     

Flexible multi-state nonvolatile antiferroelectric memory

A rapid surge on the research of nonvolatile memory is occurring with the explosion of information data. However, the realization of multi-state memory with enhanced storage capability remains a challenge, especially toward the bio-integrated/wearable electronics. In this work, we propose an unprecedented flexible multi-state data storage strategy based on antiferroelectric film (i.e., PbZrO₃) with the assistance of unique mica substrates. These flexible PbZrO₃ films exhibit remarkable durability and flexibility, that is, as high as 10⁶ times bending with radii as small as 5 mm is achieved, the best activity reported so far for flexible antiferroelectric films. Most importantly, the memory endures 10⁸ electrical write/read cycles and works properly reaching 390 K. These findings can provide new pathways for the development of the next-generation multi-state memory in smart wearable devices or flexible display screens.     

Excellent energy-storage property and thermal stability of PLZT-based antiferroelectric ceramics

(Pb, La)(Zr, Ti)O₃ antiferroelectric (AFE) materials are promising materials due to their energy-storage density higher than 10 J cm⁻³, but their low energy-storage efficiency and poor temperature stability limit their application. In this paper, the (1 − x)(Pb_0.9175La_0.055)(Zr_0.975Ti_0.025)O₃–xPb(Yb_1/2Nb_1/2)O₃ (PLZTYN100x) AFE ceramics were prepared via two-step sintering method and investigated thoroughly. With the doping of Yb³⁺ and Nb⁵⁺, the phase structure transforms from the orthorhombic phase (AFE_O) to the coexistence of the orthorhombic-and-tetragonal phases. This structure reduces the free energy difference between the AFE and ferroelectric phases and reduces the fluctuation of energy with temperature, improving the energy storage efficiency and temperature stability. When the x = 0.05 (PLZTYN5), the AFE ceramic exhibits excellent temperature stability and ultrahigh energy storage performance, whose recoverable energy density (W_rec) is 6.8–8.2 J cm⁻³ at 30 kV mm⁻¹ in the temperature range from −55 to 75°C, and efficiency (ƞ) is 78%–86.7%. In addition, the change of W_rec is less than 15%, exceeding the performance of most AFE ceramics. The results demonstrate that the PLZTYN5 ceramic has great potential in pulse power capacitors.     

Excellent energy-storage properties of NaNbO3-based lead-free antiferroelectric orthorhombic P-phase (Pbma) ceramics with repeatable double polarization-field loops

The energy-storage performance of stable NaNbO₃-based antiferroelectric (AFE) ceramics was for the first time reported in (0.94-x)NaNbO₃-0.06BaZrO₃-xCaZrO₃ lead-free ceramics. A gradual evolution from an instable AFE phase (x≤0.01) to an orthorhombic AFE P phase (Pbma) (0.01<x≤0.05) was found to accompany the appearance of repeatable double-like polarization versus electric field loops although poled samples (x<0.01) own an AFE monoclinic phase (P2₁). Interestingly, compared with x≤0.01 samples with instable antiferroelectricity, a relatively high recoverable energy storage density W_rec ? 1.59 J/cm³ (@ 0.1 Hz) and a storage efficiency η of ?30% were achieved in the x = 0.04 ceramic. Moreover, a high W_rec of > 1.16 J/cm³ and an outstanding charge-discharge performance with fast discharge rate (t_0.9 < 100 ns) were generated in the temperature range from room temperature to 180 °C in the x = 0.04 ceramic. These results suggest that NaNbO₃-based AFE P-phase ceramics could be new potential dielectric materials for high-energy storage capacitors.     

Evolving antiferroelectric stability and phase transition behavior in NaNbO3-BaZrO3-CaZrO3 lead-free ceramics

The stability of antiferroelectricity in NaNbO₃ ceramics was found to evolve with co-doping x mol% CaZrO₃ and 6 mol% BaZrO₃, from a dominant ferroelectric (FE) orthorhombic Q phase (x = 0) to a gradually stabilized antiferroelectric (AFE) orthorhombic P phase owing to different ionic radii of Ba and Ca ions. Although a complete AFE P phase appears at x = 0.5, the field induced AFE-FE phase transformation is irreversible at first, and then becomes partially reversible at x = 1 and finally completely reversible at x = 3. The above-mentioned change process proves to be associated with the enhancing stability of antiferroelectricity with x, as evidenced by means of dielectric, polarization and strain properties as well as in/ex-situ synchrotron x-ray diffraction and Raman spectra. A composition-field phase diagram for the NN-based lead-free AFE ceramic was constructed on basis of the phase structural change, which would provide a clear understanding of how ion doping influences its antiferroelectricity.     

High energy storage performance in Ca-doped PbZrO3 antiferroelectric films

In this work, antiferroelectric Pb_1-xCa_xZrO₃ (PCZ) thin films with different concentrations of Ca²⁺ were prepared by chemical solution deposition, and the effects of Ca²⁺ concentration on the antiferroelectric properties and energy storage performance were investigated. The results show that the optimal Ca²⁺ concentration in the PCZ thin films is x = 0.12 for electric properties and energy storage performance. The recoverable energy storage density and energy storage efficiency is 50.2 J/cm³ and 83.1 % at 2800 kV/cm, which is 261 % and 44.8 % higher than those of the PbZrO₃ (PZ) films. These effects are attributed to the enhancement of stability of antiferroelectric phase, diffuseness in the field-induced phase transition and electric breakdown strength by Ca²⁺-doping in the PZ films. Our results demonstrate that doping an appropriate amount of Ca²⁺ ions in antiferroelectric thin films is an effective way to improve their energy storage performance.     

Effects of phase transition on discharge properties of PLZST antiferroelectric ceramics

The effects of electric field‐induced phase transition on discharge properties of Pb_0.94La_0.04[(Zr_0.52Sn_0.48)_0.84Ti_0.16]O₃ antiferroelectric (AFE) ceramics were investigated. Due to the forward phase transition, high polarization and energy density are achieved. The backward phase transition results in nonlinear increase of current in underdamped circuit. The stored charge (14.2 μC under 40 kV/cm at 22°C) can be released completely in very short duration due to the low remanent polarization. With increasing temperature, the polarization and releasable energy decline. However, the current amplitude reaches maximum at 40°C, which is attributed to the backward phase transition. The maximum current and power density are as high as 143.8 A/cm² and 2.4 MW/cm³, which indicates the potential of the ceramics for pulsed capacitors.     

Effects of A-site ionic size on the phase transition behavior of lead-free niobate ceramics

Understanding the phase structure evolution is important for developing high performance lead-free piezoelectric materials. In this work, the effects of A-site ionic size of monovalent ions on the phase transition behaviors for the lead-free niobate ceramics ANbO₃ (A = Li, Na, Ag, and K) are investigated using XRD analysis and dielectric measurement. The iso-valent ionic doping restrains the relaxation behavior that usually appears in the hetero-valent ionic-doped niobate ceramics. The A-site average ionic size of R_A and its ionic radius differences of ΔR_A are found to be crucial influence factors on the phase transition behaviors of the ANbO₃ ceramics. Small Li⁺ doping stabilize tetragonal phase of the ANbO₃ ceramics with R_A > 1.47 Å, but stabilize rhombohedral phase of the ones with R_A < 1.47 Å. On the other hand, The ANbO₃ ceramics without Li⁺ doping prefer to orthorhombic phase due to indistinctive ionic size differences (ΔR_A < 0.25 Å). Our results suggest that a certain phase and phase transition boundary could be designed by appropriate ionic doping for developing the niobate-based lead free piezoelectric ceramics.     

Ameliorative energy-storage properties stemmed from the refined grains in PBLZS antiferroelectric ceramics via introducing liquid phase sintering

The low breakdown strength (BDS) of antiferroelectric ceramics, which become failure before undergoing electrical field induced antiferroelectric-ferroelectric phase transition, have seriously restricted the progress of pulsed power capacitors. The method of refining grain sizes via the incorporation of glass additive is supposed to be an outstanding strategy to boost the BDS. Herein, the (Pb_0.91Ba_0.015La_0.05)(Zr_0.6Sn_0.4)O₃ (PBLZS) antiferroelectric ceramics with the introduce of BaO-B₂O₃-Al₂O₃-SiO₂ (BBAS) glass are designed and synthesized by a traditional solid-state reaction. When the glass content is 0.4 wt%, the recoverable energy storage density (W_rec) increases by 215 % from 2.0 J/cm³ to 6.3 J/cm³, together with a greatly enhanced BDS up to 390 kV/cm versus 270 kV/cm of pure ceramics. Meanwhile, the corresponding sintering temperature is remarkably decreased from 1300℃ to 1100℃. The superior charge and discharge performance can be obtained under the electrical field of 310 kV/cm, including a giant current density (1184.7 A/cm²), a high power density (184.2 MW/cm³), and an ultra-fast discharge period (40 ns). The prominent energy storage properties and low sintering temperature make it become a good candidate for fabricating multilayer pulsed power ceramic capacitors.     

Phase transition and energy storage behavior of antiferroelectric PLZT thin films epitaxially deposited on SRO buffered STO single crystal substrates

(Pb_0.98, La_0.02)(Zr_0.95, Ti_0.05)O₃ (PLZT) thin films of 300 nm thickness were epitaxially deposited on (100), (110), and (111) SrTiO₃ single crystal substrates by pulsed laser deposition. X-ray diffraction line and reciprocal space mapping scans were used to determine the crystal structure. Tetragonal ((001) PLZT) and monoclinic M_A ((011) and (111) PLZT) structures were found, which influenced the stored energy density. Electric field-induced antiferroelectric to ferroelectric (AFE→FE) phase transitions were found to have a large reversible energy density of up to 30 J/cm³. With increasing temperature, an AFE to relaxor ferroelectric (AFE→RFE) transition was found. The RFE phase exhibited lower energy loss, and an improved energy storage efficiency. The results are discussed from the perspective of crystal structure, dielectric phase transitions, and energy storage characteristics. Besides, unipolar drive was also performed, providing notably higher energy storage efficiency values due to low energy losses.