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The 0.95K0.42Na0.58Nb0.96Sb0.04O3–0.02BaZrO3–0.03Bi0.5K0.5HfO3 ceramic was fabricated via a conventional solid-state reaction. This ceramic exhibits the diffuse polymorphic phase boundary (PPB) near room temperature. The dielectric, ferroelectric, electromechanical, electrocaloric, and dielectric energy storage properties were studied systemically. The normalized large signal d33* values are approximately 400–600 pm/V at measured temperatures and electric fields, which are larger than or comparable with the values reported in other lead-free compositions. The electrocaloric strength is enhanced at the broad region of PPB provided by the indirect and direct measurements. At low field of 30 kV/cm, the dielectric energy storage is ∼0.12–018 J/cm3 at relative broad temperature range due to the diffuse nature of polymorphic phase boundary. Theoretical simulations reveal that multi-element dopants, such as Sb5+, Hf4+, Zr4+, and Bi3+ ions, could induce the breaking of local structure symmetry in the orthorhombic phase to form the PPB. In addition, the charge distribution may also break the long-range ferroelectric order through the analysis of Bader charge. Our study suggests that the K0.5Na0.5NbO3-based ceramic exhibits improved performance and good thermal stability in piezoelectric, electrocaloric, and dielectric energy storage characteristics in terms of the design of multi-element dopants to form the PPB and it will benefit the promising applications in electronic devices. [ABSTRACT FROM AUTHOR]

In this work, the electrocaloric (EC) effect was studied in the (100- x)BaHf 0.2 Ti 0.8 O 3 - x Ba 0.94 Sm 0.04 TiO 3 (BHT- x BST) ceramics fabricated by the conventional solid-reaction method. By tuning composition to their diffuse phase transition (DPT), invariant critical point (ICP) and first-order phase transition (FPT), the large electrocaloric response with a temperature change of ΔT = 0.46 °C (at 64 °C) under 30 kV/cm and an electrocaloric strength of ΔT/ΔE = 0.18 K mm/kV under 12 kV/cm were achieved in BHT-70BST. In addition, BHT-50BST shows a broad EC working temperature window from 28 °C to 68 °C because of its diffusion behavior near the ferroelectric-to-paraelectric phase transition and multiphase coexistence. The maximum ΔT of BHT-50BST is larger than that of BHT-40BST with only diffusion character but no multiphase coexistence. This work may provide a design strategy to enhance EC performance with a broad working temperature region in lead-free rare-earth doped BaTiO 3 -based ceramics by combining the diffusion behavior, multiphase coexistence and heterovalent substitution. [ABSTRACT FROM AUTHOR]

In this work, the (100-x)Ba(Hf 0.2 Ti 0.8 )O 3 -x(Ba 0.7 Ca 0.3 )TiO 3 (BHT–xBCT) ferroelectric ceramics were fabricated by a conventional solid-state reaction method. The electrocaloric effect (ECE) of these ceramics was studied by both indirect and direct methods over a wide temperature range with the composition changing from x = 20 to 50. The most excellent direct ECE occurs in the BHT–50BCT with a good direct ΔT EC = 0.27 K (at 92 °C) under the electric field of 10 kV/cm. What's more, the direct EC effect peaks not only locates at near the Curie temperature, but also at the phase-transition temperatures corresponding to the transitions between different ferroelectric phases. In particular, it is found that BHT–50BCT exhibits a direct ECE anomaly ΔT EC = 0.1 K at 30 °C under an electric field of 10 kV/cm, which can be ascribed to the orthorhombic to tetragonal phase transition, proposing that one can achieve a broad temperature window by tuning the temperature gap between ferroelectric (FE) to paraelectric (PE) boundary and FE-FE boundary. In addition, BHT–30BCT shows good stability of indirect ΔT EC,max /ΔE and a broad ECE peak at a higher electric field, indicating that it is possible for electrocaloric temperature ΔT EC to be tuned linearly by electric field. Overall, our results imply that the BHT– xBCT ceramics are promising candidates for lead-free cooling refrigeration applications. [ABSTRACT FROM AUTHOR]

In this work, Ni-doped SrBi 2 Nb 2 O 9 (Sr 1- x Bi 2+ x Nb 2- x Ni x O 9- x , or SBNN) ceramics were successfully fabricated by using a solid state reaction method, and their band gaps were determined by UV–vis–NIR absorption spectrum. It is found that Ni doping could significantly reduce the band gap of SrBi 2 Nb 2 O 9 . The Sr 0.91 Bi 2.09 Nb 1.91 Ni 0.09 O 8.91 (SBNN9) ceramics show the lowest band gap of 2.25 eV with a relatively high remanent polarization of 2.5 μC/cm 2 . The band-gap reducing effect upon Ni doping might be attributed to the formation of the intermediate gap states generated by the Ni 2+ cations. Despite oxygen vacancies were unavoidably introduced into the systems after Ni doping, the remanent polarizations of the SBNN ceramics remain almost the same or even larger than the pure SrBi 2 Nb 2 O 9 . Our experimental results are also confirmed by the theoretical analysis based on the first-principle calculations. Novel ferroelectric photovoltaic effects were observed in these SBNN compounds. The switchable photovoltaic outputs induced by electric field were detected along different poling directions in the SBNN9 sample. The SBNN ceramics reported in the present work display narrow band gaps and relatively large polarizations, and show promise for ferroelectric photovoltaic device applications. [ABSTRACT FROM AUTHOR]

0.8(Bi 0.5 Na 0.5 )TiO 3 −0.2(Bi 0.5 K 0.5 )(Hf x Ti 1−x )O 3 (abbreviated as BNT-BKH x T 1−x ) lead-free ceramics are prepared using a solid state reaction method and their dielectric, field-induced strain and energy storage properties have been systemically investigated. It was found that the largest strain induced by an external electric field occurs for x=0.02. For the x=0.02 sample, S 33 =0.41%, S max /E max =683 pm/V. However, the energy storage density is optimized at the x=0.03 sample, for which W 1 =0.51 J/cm 3 . Those results may originate from the field-induced transition between a relaxor-ferroelectric mixture phase and a ferroelectric phase. [ABSTRACT FROM AUTHOR]

AgNbO3 (AN)-based lead-free antiferroelectric ceramics are widely studied for their use as dielectric capacitor materials. In this study, Eu3+-doped AN ceramics were prepared and the results show that Eu3+ diffused into the AN lattice. The ceramics were formed by M1 and M2 phases coexisting at room temperature, as distinct from the M1 (M: monoclinic) phase of pure AN. Electrical properties and structural characterization showed that the antiferroelectric stability of the ceramics increases with the increase in Eu3+ levels. At room temperature, Ag0.94Eu0.02NbO3 ceramic exhibited a good energy storage density of 5.3 J/cm3 and a high efficiency of 71.9%. When the temperature rises from room temperature to 140 °C, the efficiency of the sample decreases from 80.4% to 67.1% and Wr decreases from 2.1 to 2.0 J/cm3, which indicates that the sample has good temperature stability. The time constant (t0.9) of this sample was less than 60 ns and the power density (PD) was 51.3 MW/cm3, indicating excellent charge–discharge capabilities. This novel ceramic is expected to be used as a new dielectric capacitor material for pulsed power supplies. [ABSTRACT FROM AUTHOR]

The order-degree-modulated ferroic response and electrocaloric effect (ECE) in Pb(B1,B2)O3-type B-site complex antiferroelectrics (AFEs) are explored in this work. The results show that local/phase structure and dielectric/ferroic properties are strikingly dependent on the degree of order (high, intermediate and low for samples S1, S2 and S3, respectively). A decrease in the content of the AFE orthorhombic phase and an increase in the weakly polar disorder phase is observed from S1 to S3, accompanied by an enhanced relaxation behavior with a smearing of the AFE-to-paraelectric phase transition. Ferroic and EC responses in the three samples present distinct features. Antiferroelectricity wakes-up significantly in sample S1, which boosts the ECE to ∼0.95 K and is almost three times that of S3 (∼0.23 K). An abnormal ECE [negative ECE with a hop–hop character and asymmetrical electrocaloric (EC) response] is unexpectedly found in sample S1. The underlying mechanism is unveiled by dipolar relaxation and phenomenology analysis, which states that the AFE coupling strength dominates the EC performance in this AFE. This work not only presents a refreshing method for order-degree regulation of the ECE in B-site complex AFEs, but also clarifies the possibility that AFEs with robust dipolar coupling strength have an unconventional ECE. [ABSTRACT FROM AUTHOR]

We report a giant strain (0.72%) with a low degree of hysteresis ( ca . 36.2%) and a giant S max / E max ratio (916 pm V −1 , S max and E max denote the maximum strain and the corresponding electric field, respectively) for lead-free (1− x )(0.8Bi 0.5 Na 0.5 TiO 3 -0.2Bi 0.5 K 0.5 TiO 3 )- x Sr 0.8 Bi 0.1 □ 0.1 Ti 0.8 Zr 0.2 O 2.95 piezoceramics with x = 0.06. The giant strain originates from a reversible transition between the ergodic relaxor and ferroelectric states under applied electric fields. A-site vacancies (V A ) and oxygen vacancies (V O ), deliberately introduced to the system, induce a randomly distributed local polarization field. The local field induces embryonic polarization domains that have a broad distribution of maturity and thus smears the transition between the ferroelectric and relaxor states. This leads to a narrow hysteresis loop. The poling field required for the relaxor-to-ferroelectric transition is reduced significantly, due to the remanent ferroelectric phase at zero field acting as the seed, and the point defects synergistically facilitating the nucleation and growth of the ferroelectric phase. Our work provides a novel route for designing piezoelectric materials with both a giant strain and a narrow hysteresis for practical actuator applications. [ABSTRACT FROM AUTHOR]

Polarization fatigue in (Pb 0.97 La 0.02 )(Zr 0.95 Ti 0.05 )O 3 (PLZT) antiferroelectric thin films deposited onto silicon wafers is studied by investigating the effect of the peak/average/root-mean-square cycling voltage through varying the waveform of the electrical excitation. Interestingly, it is found that the fatigue behavior of the film is determined by the root-mean-square voltage of the external driving excitation rather than by the peak or average voltages. Our results can be well explained in the framework of the local phase decomposition model and indicate that the root-mean-square voltage should be considered as the effective driving voltage determining the polarization fatigue in PLZT antiferroelectric films. [ABSTRACT FROM AUTHOR]

Abstract: Electron emission from antiferroelectric Pb0.99[(Zr0.90Sn0.10)0.96Ti0.04]0.98Nb0.02O3 ceramics, which can maintain a metastable ferroelectric state subject to a high electric field, was systematically investigated. In line with previous conclusions, the primary electrons emitted from the triple junction can induce the surface plasma so as to result in large emission current. Thus, the electric field of the triple-junction region is significant for electron emission. For the first time, we report that the electric field of this special region is determined by the high-field relative permittivity, rather than the small-signal relative permittivity. Finally, it was confirmed that the initial emission field, the emission threshold field, and the stable emission field all decrease as the high-field relative permittivity increases. [Copyright &y& Elsevier]

Paraelectric-ferroelectric-antiferroelectric (PE-FE-AFE) phase transitions induced by external stimulus (temperature, electric field, and hydrostatic pressure) usually produce exotic performances in functional ceramics. This Letter reports an isothermal phase transition in (Pb0.95Ba0.05)ZrO3 ceramics in the proximity of separated PE-FE and FE-AFE phase boundaries as extended waiting time. Through an isothermal process, PE (Pm 3 ¯ m)-to-FE (R3cH) and FE-to-AFE (Pbam) phase transformations occur within several minutes (with different transition degrees). This is in contrast to the wide recognition of ultrafast and time-independent ferroelectric transitions. In situ Raman spectra analysis unveils the sluggish growth of FE and AFE phases out of the corresponding parent matrix. Finally, the Landau theory analysis is proposed to explain the isothermal phase transition among PE-FE-AFE phases. This work will refresh the wisdom of phase transitions in functional ceramics. [ABSTRACT FROM AUTHOR]

The lead-free Ba 0.53 Sr 0.47 TiO 3 (BST) thin films buffered with La 0.67 Sr 0.33 MnO 3 (LSMO) bottom electrode of different thicknesses were fabricated by pulsed laser deposition method on a (001) SrTiO 3 substrate. It was found that the roughness of electrode decreases and substrate stress relaxes gradually with the increase of LSMO thickness, which is beneficial for weakening local high electric field and achieving higher E b. Therefore, the recoverable energy density (W rec) of BST films can be greatly improved up to 67.3 %, that is, from 30.6 J/cm3 for the LSMO thickness of 30 nm up to 51.2 J/cm3 for the LSMO thickness of 140 nm after optimizing the LSMO thickness. Furthermore, the thin film capacitor with a 140 nm LSMO bottom electrode shows an outstanding thermal stability from 20 °C to 160 °C and superior fatigue resistance after 108 electrical cycles with only a slightly decrease of W rec below 1.6 % and 3.7 %, respectively. Our work demonstrates that optimizing bottom electrodes thickness is a promising way for enhancing energy storage properties of thin-film capacitors. [ABSTRACT FROM AUTHOR]

The conductive characteristics of Bi0.9La0.1Fe0.96Mg0.04O3 (BLFM) thin film are investigated at various temperatures and a negative differential resistance (NDR) is observed in the thin film, where a leakage current peak occurs upon application of a downward electric field above 80 °C. The origin of the NDR behavior is shown to be related to the ionic defect of oxygen vacancies (VO••) present in the film. On the basis of analyzing the leakage mechanism and surface potential behavior, the NDR behavior can be understood by considering the competition between the polarized distribution and neutralization of VO••. [ABSTRACT FROM AUTHOR]

Abstract The Na 0.47 Bi 0.47 Ba 0.06 Ti 1- x Fe x O 3-Δ lead-free piezoelectric ceramics (BNBT-100 x Fe, x = 0, 0.01, 0.02, 0.03) were synthesized by using the solid-state reaction technique. X-ray powder diffraction patterns demonstrate that the doping Fe 2 O 3 has totally diffused into the crystal lattice of the ceramics and form a pure perovskite structure. Enhanced piezoelectric property is obtained at x = 0.01, which is reflected on the enhanced remnant polarization (P r) and a giant piezoelectric constant (d 33) up to 168 pC/N. The increasing ferroelectric-to-relaxor phase transition temperature (T F-R) on dielectric permittivity curves suggest the enhanced ferroelectric characteristics with increasing the Fe3+ content. By using the complex ac impedance analysis, the grain, grain boundary and electrode effects are all detected at the appreciate composition. The resistivity behavior of the samples is sensitive to the doping Fe3+ concentration, and additionally, the oxygen vacancies play an important role in this characteristic. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we fabricated the (1‐x)BiFeO3‐xBaTiO3+y‰ mol CuO ceramics by the modified thermal quenching technique. The pure perovskite phase was formed and a morphotropic phase boundary (MPB) was observed in the ceramics with x = 0.30‐0.33. The addition of CuO can significantly enhance the density of the BiFeO3‐BaTiO3 material. Importantly, an enhanced piezoelectric constant (d33=165 pC/N), a large electric‐field‐induced strain (∆S = 0.54%: peak to peak strain) and a large piezoelectric actuator constant (d33*=449 pm/V) together with a high Curie temperature (TC) of 503°C were observed in the ceramics with x = 0.30 and y = 5. As a result, the enhanced piezoelectricity and large electric‐field‐induced strain could significantly stimulate further researches in BFO‐based ceramics. [ABSTRACT FROM AUTHOR]

A series of (Bi 0.5 Na 0.4 K 0.1 )Ti 0.98 Nb 0.02 O 3 - x Li lead-free ceramics were fabricated using the solid-state reaction technique. The effects of Li/Nb cations on the structural and electrical properties of the ceramics were investigated. All the sintered ceramics exhibited pure perovskite structure and the average grain size increased slightly with increasing the Li content. Shape of the P - E loops illustrated the relaxor characteristic of all the samples. A giant strain of 0.4% was obtained at 60 kV/cm at x = 0.01 and the corresponding normalized strain was up to 683 pm/V, moreover, the strain exhibits excellent fatigue-resistance behavior. The giant strain can be attributed to the ferroelectric-relaxor phase transition under external driving electric field. These results indicate the sintered Li/Nb co-doped lead-free ceramics can be promising candidate for actuator applications. [ABSTRACT FROM AUTHOR]

Using the first‐principles approaches, we obtain a phase diagram of AgNbO3 as a function of in‐plane epitaxial strain, and two phase transitions (from Pm to Cm and from Cm to Amm2) were found throughout the whole range of strain. In particular, our study shows that the antiferrodistortion (AFD) is misfit‐dependent. Our results indicate that compressive in‐plane lattice strain can enhance the AFD instability of AgNbO3, which originates from the stronger coupling between the out‐of‐plane lattice strain and AFD than coupling with in‐plane lattice strain. In order to overcome the overestimation of rotational angle caused by the underestimation of lattice parameters, we construct a Gibbs free energy under a certain external pressure to obtain a reasonable angle, which is about 8.39°. We expect our results may offer some insights for designing and fabricating AgNbO3 thin films with excellent antiferroelectric properties by using compressive strain engineering. [ABSTRACT FROM AUTHOR]

A series of Nb-doped (BiNaK)TiO lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method. The X-ray diffraction patterns reveal a pure perovskite structure for all the samples. A giant strain of 0.34% is achieved at 2 mol% Nb-doping concentration, and the corresponding normalized strain $$d_{33}^*$$ reaches 625 pm V, which is one of the best results of the BNT-based ceramics. Complex ac impedance data indicate that only the bulk effect contributes to the resistivity. The compositionally induced disruption of long-range ferroelectric order and relaxor transition contributed to the pinched polarization loops as well as the large electric field-induced strain. The results indicate that appropriate Nb-dopant content can remarkably enhance the strain level of (BiNaK)TiO ceramics, making it a promising candidate for actuator applications. [ABSTRACT FROM AUTHOR]

Piezoelectric acoustic emission sensors can be used detect the sound emitted by the target structure when it is damaged and have important applications in the field of structure health monitoring. However, due to the mismatch of the interface acoustic impedance, it is hard for the conventional ultrasonic sensor to monitor the acoustic emission in a pipe structure. In this work, a flexible sensor by the deposition of a Pb(Zr0.52,Ti0.48)O3 thin film on a mica substrate was fabricated, and the acoustic emission generated by the partial discharge of a 110 kV power cable was detected by using the flexible sensor. The flexible sensor was designed with an electromagnetic shielding structure and, therefore, can screen most of the electromagnetic interference. The flexible sensor shows a relatively flat response in the frequency range from 100 to 1000 kHz with a sensitivity over 47.5 dB, which is beneficial for pattern recognition studies of acoustic emission. This work not only provides a flexible, anti-electromagnetic interference and broadband sensor for acoustic emission detection but also promotes the development and application of flexible ferroelectric materials. [ABSTRACT FROM AUTHOR]

Dielectric capacitors are widely used in pulsed power electronic devices due to their ultrahigh power densities and extremely fast charge/discharge speed. To achieve enhanced energy storage density, maximum polarization (Pmax) and breakdown strength (Eb) need to be improved simultaneously. However, these two key parameters are inversely correlated. In this study, order–disorder transition induced polar nanoregions have been achieved in PbZrO3 thin films by making use of the low-energy ion implantation, enabling us to overcome the trade-off between high polarizability and breakdown strength, which leads to the tripling of the energy storage density from 20.5 to 62.3 J/cm3 as well as the great enhancement of breakdown strength. This approach could be extended to other dielectric oxides to improve the energy storage performance, providing a new pathway for tailoring the oxide functionalities. [ABSTRACT FROM AUTHOR]

Phase transition is expected in designing high-performance electrocaloric effect (ECE). However, hidden antiferroelectricity in NaNbO3-based ceramics complicates ECE evolution as compared to conventional ferroic materials. Therefore, a NaNbO3−xBi0.5Li0.5TiO3 (x = 0.08, 0.10, and 0.12) system is introduced to explore ECE performance in P (Pbma), Q (P21ma), and R (Pnma) phases since a Bi0.5Li0.5TiO3 dopant plays a Janus role in stabilizing ferroelectric Q (x = 0.08 and 0.10) and inducing the antiferroelectric (AFE) relaxor R phase (x = 0.12). Rietveld refinement reveals a phase structure change from the P/Q to R state. Bi0.5Li0.5TiO3 addition makes a downshift of P-to-R transition temperature accompanied by an increase in relaxation property, as certified by dielectric analysis/piezoelectric force images, in situ XRD/Raman spectra, and ferroelectric tests. Additionally, a square P–E loop evolves into less-sharp and finally changes into a slant one with increasing Bi0.5Li0.5TiO3 content. ECE is directly measured, and its peak value increases from 0.15 K for x = 0.08 and 0.21 K for x = 0.10 and finally to 0.11 K for x = 0.12 composition. Interestingly, dual ECE peaks appear in x = 0.10, and it is probably contributed by R relaxor polar nanodomains. This work not only clarifies actual ECE behavior in AFE orthorhombic (P/R) NaNbO3-based ceramics but also fulfills understandings of AFE P-to-R transitions in modulating ECE. [ABSTRACT FROM AUTHOR]

Lead‐based antiferroelectric (AFE) ceramics have attracted increasing interest in pulse power systems owing to their high‐energy storage and power densities. However, the single AFE–ferroelectric (FE) phase transition in conventional AFE materials usually leads to premature polarization saturation and low breakdown strength, which are disadvantageous to energy storage performance. In this study, high energy storage performance was achieved in Pb0.94−xLa0.04Cax[Nb0.02(Zr0.99Ti0.01)0.975]O3 (PLCNZT) AFE ceramics by constructing electric‐field‐induced multiple phase transitions. A maximum recoverable energy storage density of 12.15 J/cm3 and a high energy efficiency of 85.4% were obtained for the PLCNZT ceramic with x = 0.03 at 420 kV/cm. These excellent properties are attributed to the AFE–FE Ⅰ‐FE Ⅱ multiple phase transitions induced by Ca2+ doping, which effectively enhances the breakdown strength. This result indicates that field‐induced multiple phase transitions significantly improve the energy storage of AFE materials. [ABSTRACT FROM AUTHOR]

The capacitance dispersion in La and Mg co-substituted BiFeO3 thin film has been studied at different stages of polarization switching. A negative capacitance (NC) behavior is observed in the sample that is fatigued above 109 switching cycles. The origin of the NC is investigated through analyzing relaxation processes and charge transport kinetics by admittance spectroscopy. An activation energy of ∼0.6 eV and a zero field mobility μ0=5.33±0.02×10-13m2/Vs are thus obtained. A physical mechanism is proposed to explain this behavior. It involves a redistribution of oxygen vacancies, which are trapped at the film/electrode interface during the fatigue process. [ABSTRACT FROM AUTHOR]

Bismuth sodium titanate (BNT)‐based lead‐free piezoceramics are promising for replacing lead‐based piezoceramics in piezoelectric actuators due to their large strains. However, achieving low‐hysteresis large‐strain BNT‐based ceramics over a broad temperature range is challenging, owing to the complexity of the composition design and phase transformation. Herein, a lead‐free relaxor‐ferroelectric (1−x)Bi0.47Na0.47Ba0.06TiO3‐xK0.47Na0.47Li0.06Nb0.99Sb0.01O2.99 system (BNBT‐KNLNS) near the morphotropic phase boundary (MPB), achieved by phase‐field simulations and rational composition design (i.e., BNBT with the MPB as the base and the ferroelectric phase of KNLNS as the dopant) is reported. This ceramic exhibits large strains (0.32–0.51%) and low strain hysteresis (11.1–59.9%) over a wide temperature range (25–125 °C), outperforming many state‐of‐the‐art lead‐free piezoceramics. A small fraction of ferroelectric states embedded in the relaxor matrix is experimentally observed, where these states act as seeds, facilitating the reversible relaxor‐to‐ferroelectric transition. In addition, the MPB composition with low energy barriers yields large strain responses, owing to the easy polarization reversal and extension. Consequently, low‐hysteresis large strains are obtained over a broad temperature range. This work provides a novel design route for discovering high‐performance piezoceramics for actuator applications. [ABSTRACT FROM AUTHOR]

• Tailoring the first-order O-T phase transition strategy was adopted in this work. • The large Δ T of 0.3 K is attained in 0.6BST-0.4BZT ceramic at room temperature. • The Δ T of 0.53 K is achieved at 342 K due to the quadruple point coexistence. The development of refrigeration technology has burgeoned in response to the challenges posed by global warming. Notably, electrocaloric materials have garnered significant attention for their potential in miniaturization and high efficiency. However, investigations into the electrocaloric response in proximity to orthorhombic-tetragonal phase transition in BaTiO 3 -based ferroelectric ceramics remain scarce. In this study, we employ a lead-free x (Ba 0.7 Sr 0.3)TiO 3 -(1- x)Ba(Zr 0.2 Ti 0.8)O 3 polycrystalline ceramics fabricated through the solid-state reaction method. The comprehensive analysis includes elucidation of the phase structure, surface morphologies, dielectric properties, domain switching behavior, and the electrocaloric effect. Integrating these findings with the phase diagram unveils optimal adiabatic temperature change (Δ T) achieved within the quadruple point coexistence region. That is, the highest Δ T of 0.53 K is achieved for x = 0.4 ceramic, which is attributed to the increased entropy resulting from multiple polar phases. Remarkably, the highest Δ T of 0.3 K is attained in x = 0.6 ceramic under a low driving electric field of 30 kV/cm at room temperature, precisely within the orthorhombic-tetragonal transition temperature. The investigation underscores the efficacy of regulating the first-order orthorhombic-tetragonal phase transition to achieve exceptional electrocaloric responses at room temperature. [ABSTRACT FROM AUTHOR]

Ferroelectrics with a high dielectric constant are ideal materials for the fabrication of miniaturized and integrated electronic devices. However, the dielectric constant of ferroelectrics varies significantly with the change of temperature, which is detrimental to the working stability of electronic devices. This work demonstrates a new strategy to design a ferroelectric dielectric with a high temperature stability, that is, the design of a multilayer relaxor ferroelectric thin film with a composition gradient. As a result, the fabricated up-graded (Pb,La)(Zr0.65,Ti0.35)O3 multilayer thin film showed a superior temperature stability of the dielectric constant, with variation less than 7% in the temperature range from 30 °C to 200 °C, and more importantly, the variation was less than 2.5% in the temperature range from 75 °C to 200 °C. This work not only develops a dielectric material with superior temperature stability, but also demonstrates a promising method to enhance the temperature stability of ferroelectrics. [ABSTRACT FROM AUTHOR]

Fatigue failure in ferroelectrics has been intensively investigated in the past few decades. Most of the mechanisms discussed for ferroelectric fatigue have been built on the “hypothesis of variation in charged defects”, but these are rarely evidenced by experimental observation. Here, using a combination of complex impedance spectra techniques, piezoresponse force microscopy and first-principles theory, we examine the microscopic evolution and redistribution of charged defects during the electrical cycling in BiFeO 3 thin films. The dynamic formation and melting behaviors of oxygen vacancy ( V O ) order are identified during the fatigue process. It reveals that the isolated V O tends to self-order along grain boundaries to form a planar-aligned structure, which blocks the domain reversals. Upon further electrical cycling, migration of V O within vacancy clusters is accommodated with a lower energy barrier (∼0.2 eV) and facilitates the formation of a nearby-electrode layer incorporated with highly concentrated V O . The interplay between the macroscopic fatigue and microscopic evolution of charged defects clearly demonstrates the role of ordered V O clusters in the fatigue failure of BiFeO 3 thin films. [ABSTRACT FROM AUTHOR]

Dielectric capacitors, as one of the important electronic devices, are widely used in various fields. However, most ferroelectric capacitors with high energy storage density require excessively high electric fields. In this work, we have prepared 0.9(Bi0.5Na0.5)0.7Sr0.3TiO3-0.1 Bi(Mg2/3Nb1/3)O3 relaxor ferroelectric ceramics with different BaZrO3 doping levels. A high energy storage (Wr) of 4.07 J/cm3 and efficiency (η) of 91% are simultaneously obtained in 0.94[0.9(Bi0.5Na0.5)0.7Sr0.3TiO3-0.1 Bi(Mg2/3Nb1/3)O3]-0.06BaZrO3 ceramic under a medium electric field of 260 kV/cm. Additionally, the ceramic also exhibits excellent temperature and frequency stability. Furthermore, the phase field simulation is used to simulate the evolution of domain structure and hysteresis loops of the ceramics with different doping levels. The results of phase field simulation explicitly explain the influence of different relaxation degrees on energy storage density and efficiency of the ceramics. We believe that the ceramic prepared in this work is one of the most promising candidate materials for some miniaturized energy storage devices operating under low or medium electric fields. [ABSTRACT FROM AUTHOR]

• A high W r of 4.97 J/cm3 and an η of 84.4% are obtained in BNT-based ceramics. • The W r of 2.73 J/cm3 with η of 80.6% are obtained at 140 ℃. • A superior temperature performance compared with other typical dielectric materials. • A strategy of precisely adjusting the relaxation and ferroelectricity states. Dielectric energy storage materials have attracted much attention because of their wide applications in the electronics industry. However, low energy storage density and poor thermostability limit their application. In this work, a strategy was proposed to prepare lead-free relaxor ferroelectric ceramics with ultra-high energy storage properties and superior temperature stability by precisely adjusting the relaxation and ferroelectricity states and increasing the electric field intensity. An ultra-high recoverable energy storage density (W r) of 4.97 J/cm3 and an efficiency (η) of 84.4% are simultaneously obtained for the 0.95(0.9Bi 0.5 Na 0.5 TiO 3 -0.1Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3)-0.05BaSnO 3 ceramic. Moreover, a high W r of 2.73 J/cm3 with brilliant η of 80.6% are obtained in the ceramic at 140 ℃ and there is almost no thermal degradation of energy storage properties from 25 ℃ to 140 ℃. The W r and η have decreased by 2.2% and 1.9% after 105 cycles under 200 kV/cm, respectively, which demonstrates the good cycle stability of the sample. A discharge power density of up to 99.0 MW/cm3 is obtained in the 0.95(0.9Bi 0.5 Na 0.5 TiO 3 -0.1Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3)-0.05BaSnO 3 ceramic and the good charge and discharge performance of this sample is important for practical applications. [ABSTRACT FROM AUTHOR]

The 0.65(Bi 0.5 Na 0.5)TiO 3 –0.35SrTiO 3 -based materials are essential for the development of pulse power capacitors. However, their low recoverable energy storage density and breakdown field strength have hindered further improvement. To address this, a high-entropy strategy based on multiscale regulation is proposed, which involves synergistically manipulating the activation energy and microstructure evolution in BNST-based ceramics through the introduction of Ba(Zr 0.2 Ti 0.2 Sn 0.2 Hf 0.2 Ta 0.2)O 3. The inclusion of high-insulating oxides can significantly raise the activation energy of the entire system. Furthermore, the high-entropy material can significantly increase the atomic disorder and lattice distortion, resulting in strong local polar fluctuations on several nanoscales and excellent energy storage characteristics. As a result, this approach yields an impressive W rec of ∼ 4.89 J/cm3 and a high efficiency of ∼92.1 % at 351 kV/cm, and the outstanding thermal endurance (20∼150 °C), frequency stability (5∼1000 Hz) and fatigue (100∼105 cycles). This study provides an effective strategy for achieving excellent comprehensive performances in high-entropy ceramics. [Display omitted] [ABSTRACT FROM AUTHOR]

Tetragonal tungsten bronze structure (TTB) compounds have attracted tremendous interest for their applications in energy storage, especially as dielectric capacitor mediums. However, constrained by the inverse correlation of polarization and electric breakdown field in relaxor ferroelectrics, there is still a major challenge in improving energy density. To addresse this challenge, a viable strategy of constructing relaxor behavior with robust electrical insulation in TTB-type Sr 0.485 Ba 0.47 Gd 0.03 Nb 2- x Zr x O 6 (SBN-Gd-Zr x) by introducing ZrO 2 during the preparation process was proposed. By introducing Zr4+ in the B-site, we have revealed how Zr4+ affects the dielectric and ferroelectric characteristics to explore the intrinsic relaxation. Based on the analysis of Rietveld refinement against synchrotron X-ray powder diffraction and Raman results, the substitution of Gd3+ and Zr4+ for Sr2+ and Nb5+ in Sr 0.53 Ba 0.47 Nb 2 O 6 caused a decline in tetragonality and a shrinkage of the unit cell due to the lattice defect of [Gd Sr ]• and [Zr Nb ] ' , which mutually compensates effectively alleviate the distortion of BO 6 and then favors the balance of polarization and dielectric constant. The accrual of additional ZrO 2 at grain boundaries significantly enhances electrical insulation characteristics, as validated by complex impedance spectroscopy. At near room temperature, all Zr-doped SBN-Gd compounds of the series exhibit heightened relaxation and undergo a phase transition from ferroelectric to paraelectric. As a result, in tandem with the synchronous augmentation in breakdown electric field (E B) and saturation polarization (P m), optimal energy storage characteristic is realized in the SBN-Gd-Zr0.2 sample. It attains a remarkable W rec of 2.67 J/cm3 and an efficiency ƞ of 91.21 %, showcasing excellent suitability in terms of different frequencies and temperatures, which far exceeds that of Gd-modified SBN ceramics and pure SBN ceramics. These results exemplify an efficacious strategy for designing novel TTB dielectrics by coupling relaxor modulation with electrical insulation, and position them competitively for implementation in dielectric storage capacitors utilized in pulsed power devices. [ABSTRACT FROM AUTHOR]

Recently, dielectric energy storage materials and devices attracted much research interest due to its high-power density and the resulted applications. In this work, relaxor ferroelectric (Pb 1-x ,La x)(Zr 0.65 ,Ti 0.35)O 3 (abbreviated as PLZT100X, X = 0.06, 0.08, 0.10 and 0.12) thin films are deposited on Pt/Ti/SiO2/Si substrates by a sol-gel method, and temperature stability of relative dielectric constant as well as energy storage density of the PLZT thin films with different level of La doping are studied. The relative dielectric constant of the PLZT10 thin films is 873 at 1 kHz at 30°C, with maximum of variation of 7.6% in the temperature range from 30–200 °C, which indicates very high temperature stability. The energy storage density of the PLZT thin films is 38.8 J/cm3, 42.2 J/cm3, 33.5 J/cm3 and 36.0 J/cm3 with the La doping of 0.06, 0.08, 0.10 and 0.12, respectively, under the applied electric field of 2840 kV/cm. The energy efficiency of the PLZT thin films is above 70%. In addition, the energy storage density of the PLZT thin films shows good temperature stability, with about 20 J/cm3around the electric field of 1800 kV/cm in the temperature range from 30–150 °C. [ABSTRACT FROM AUTHOR]

Barocaloric effects in a layered hybrid organic–inorganic compound, (C10H21NH3)2MnCl4, that are reversible and colossal under pressure changes below 0.1 GPa are reported. This barocaloric performance originates in a phase transition characterized by different features: A strong disordering of the organic chains, a very large volume change, a very large sensitivity of the transition temperature to pressure and a small hysteresis. The obtained values are unprecedented among solid‐state cooling materials at such low pressure changes and demonstrate that colossal effects can be obtained in compounds other than plastic crystals. The temperature‐pressure phase diagram displays a triple point indicating enantiotropy at high pressure. [ABSTRACT FROM AUTHOR]

Electrocaloric effect in ultrathin SrRuO3/BaTiO3/SrRuO3 capacitors is calculated using a multiscale thermodynamic model. It is found that the electrocaloric coefficient vs working temperature is shifted to higher temperatures with increasing the BaTiO3 layer thickness (above the critical thickness). The electrocaloric effect above the critical thickness is much stronger than that below it. Furthermore, it is demonstrated that a giant electrocaloric effect (3.5 K under 0.24 V) in such capacitors (six BaTiO3 unit cells) at 300 K can be achieved, which suggests that ultrathin ferroelectric capacitors may be promising candidates for room temperature solid-state refrigeration. [ABSTRACT FROM AUTHOR]

We have studied the polarization fatigue of La and Mg co-substituted BiFeO3 thin film, where a polarization peak is observed during the fatigue process. The origin of such anomalous behavior is analyzed on the basis of the defect evolution using temperature-dependent impedance spectroscopy. It shows that the motion of oxygen vacancies (VO••) is associated with a lower energy barrier, accompanied by the injection of electrons into the film during the fatigue process. A qualitative model is proposed to explain the fatigue behavior, which involves the modification of the Schottky barrier upon the accumulation of VO•• at the metal-dielectric interface. [ABSTRACT FROM AUTHOR]

• A W r of 4.6 J/cm3 under 430 kV/cm and η of 62.5% are achieved in Ag 0.97 Nd 0.01 NbO 3. • Ag 0.97 Nd 0.01 NbO 3 ceramics demonstrate excellent temperature stability from 25 ℃ up to 125 ℃. • Outstanding power density of 54.0 MW/cm3 and ultrafast discharge speed (t 0.9) of 59.2 ns were also obtained. Lead-free dielectric capacitors for energy storage device have attracted increasing attention recently because of their high-power density and superior temperature stability. In this work, Nd-doped silver niobate (AgNbO 3 , abbreviated as AN) lead-free antiferroelectric ceramics were prepared by utilizing traditional solid state reaction method. A large energy storage density of 4.6 J/cm3 and an efficiency of 62.5% were simultaneously obtained in the 1% Nd-doped AN sample with an outstanding power density of 54.0 MW/cm3 and an ultrafast discharge speed (t 0.9) of 59.2 ns. Additionally, the 1% Nd-doped AN ceramic demonstrates a good temperature stability from 25 ℃ to 130 ℃. The excellent energy storage properties of the 1% Nd-doped ceramic is ascribed to the enhanced breakdown electric field induced by grain size engineering and the construction of phase structure via heterovalent substitution at the A-site of the lattice structure at room temperature. Our present work suggests that the 1% Nd-doped AN ceramic show promise for energy storage application in miniaturized mobile electronic devices and high-power equipment. [ABSTRACT FROM AUTHOR]

• Large recoverable energy storage density of 2.9 J/cm3 is obtained in BNT-BST-CZ ceramic. • The ceramic shows excellent dielectric permittivity stability at 44-483 °C. • The ceramic owns a fast charge-discharge speed of 110 ns. In the 0.9(0.65Bi 0.5 Na 0.5 TiO 3 -0.35Bi 0.2 Sr 0.7 TiO 3)-0.1CaZrO 3 ceramic, superior energy storage performance and excellent dielectric stability have been achieved, along with a higher discharge rate. Our finding suggests that the ceramic has great potential applications in pulsed power systems and high-temperature capacitors. [Display omitted] Novel (1− x)(0.65Bi 0.5 Na 0.5 TiO 3 -0.35Bi 0.2 Sr 0.7 TiO 3)- x CaZrO 3 (BNT-BST- x CZ, x = 0–0.15) ceramics were manufactured through a solid phase sintering process and their structural and electrical performance have been systematically investigated. By doping CaZrO 3 , a higher recoverable energy storage density of 2.9 J/cm3 and energy storage efficiency of 80% at 330 kV/cm can be simultaneously obtained in BNT-BST-0.1CZ ceramic. Further analysis with the aid of finite element simulation indicates that the improvement of energy storage performance lies in the refined grain size and reduced defects, which are both conductive to improve the dielectric breakdown strength. More importantly, incorporating CaZrO 3 gives slimmer hysteresis loops as well as excellent temperature (20–150 °C) and frequency (5–200 Hz) stability of energy storage properties. Moreover, a stable dielectric permittivity of in an ultra-wide range from 44 °C to 483 °C was achieved in BNT-BST-0.10CZ ceramic. Our findings suggest that the BNT-BST-0.1CZ ceramic has great potential applications in pulsed power systems and high-temperature capacitors. [ABSTRACT FROM AUTHOR]

Dielectric capacitors with high energy storage and dielectric properties at high temperatures have significantly practical application in many fields. Lead-free ceramics of (1- x)(0.65Bi 0.5 Na 0.5 TiO 3 -0.35Bi 0.2 Sr 0.7 TiO 3)- x BaSnO 3 were prepared by a solid-state reaction method. It was found that the 0.8(0.65Bi 0.5 Na 0.5 TiO 3 -0.35Bi 0.2 Sr 0.7 TiO 3)-0.2BaSnO 3 ceramic shows a large recoverable energy storage density (W r) of 3.75 J/cm3 and efficiency (η) of 84.8% under 380 kV/cm along with outstanding power density of 38.73 MW/cm3 under 130 kV/cm at room temperature. Additionally, a high W r of 3.21 J/cm3 and η of 77% are achieved under a high electric field of 300 kV/cm at 100 °C. When the temperature reaches 140 °C, it still has a high W r of 3.1 J/cm3 and η of 72%. The outstanding energy storage performance at high temperatures can be explained by the enhancement of breakdown strength and the constructing of polar phase stability caused by the introduction of BaSnO 3. [ABSTRACT FROM AUTHOR]

The urgent requirement of environment-friendly materials with excellent energy storage performance for pulse power systems has sparked considerable research on lead-free ceramics. In this work, a new lead-free 0.90(0.80NaNbO3–0.20Sr0.7Bi0.2TiO3)–0.10BaSnO3 ceramic with high recoverable energy storage density (Wr = 3.51 J/cm3) and decent energy storage efficiency (η = 70.85%) has been obtained. In particular, these ceramics exhibit an ultrahigh breakdown strength of 402 kV/cm due to the dense microstructure and small grain size. The impedance analysis also reveals that the incorporation of BaSnO3 is conducive to the enhancement of insulation ability and breakdown strength. Additionally, great thermal stability (ΔWr < 10% over 20–120 °C at 200 kV/cm) and fatigue resistance (ΔWr < 1% after 120,000 electrical cycles at 200 kV/cm) are observed, indicating that the 0.90(0.80NaNbO3–0.20Sr0.7Bi0.2TiO3)–0.10BaSnO3 ceramics have promising application prospect for high-temperature energy storage devices in pulse power applications. [ABSTRACT FROM AUTHOR]

• A comprehensive strategy of hybridizations of Bi3+ orbitals and relaxor was adopted. • Relaxor behavior was analyzed via Raman spectroscopy and the Curie-Weiss law. • BNT-0.40ST-0.02FN composition exhibits high W (3.36 J/cm3) and η (81%) under a low electric field of 170 kV/cm. • BNT-0.40ST-0.02FN ceramic shows superior thermal stability (25–200 °C). • The BNT-0.40ST-0.02FN ceramic possesses potential to be employed in pulsed power devices under extreme conditions. Dielectric ceramics are highly favorable for pulsed power applications owing to their ultra-fast charge-discharge speed and excellent reliability. However, their low energy density under low electric fields remains as a bottleneck for them to be employed in integrated electronic devices with shrinking dimensions. In this work, we have designed a comprehensive strategy to synthesize lead-free (Bi 1/2 Na 1/2) 1−x Sr x Ti 0.98 (Fe 1/2 Nb 1/2) 0.02 O 3 (BNT-xST-2FN, x = 0.30, 0.35, 0.40 and 0.45) ceramics via traditional solid-state method. On one hand, the hybridizations of Bi3+ orbitals and the displacement of B-site cations under the applied electric field lead to a high polarization. On the other hand, the (Fe 1/2 Nb 1/2)4+ complex-ion and SrTiO 3 were introduced to improve the relaxor behavior of the system, resulting in a high energy-storage efficiency. In this way, an excellent energy density of 3.36 J/cm3 and a high energy efficiency of 81% are simultaneously achieved in the BNT-0.40ST-0.02FN composition under a low electric field of 170 kV/cm, which is superior to other BNT-based materials under similar electric fields. Moreover, the ceramic exhibits a superior thermal stability (25–200 °C). This work provides a promising approach for designing high-performance lead-free energy storage ceramics under low electric fields. [ABSTRACT FROM AUTHOR]

• BNT-(BCT-BZT) ceramics with large strain and without negative strain were prepared • A large field-induced strain of 0.42% and large d 33 * of 547 pm/V are obtained • Large strain is mainly due to the crossover of relaxor nonpolar state to ferroelectric polar state Piezoelectric ceramics with high strain can convert electrical energy and mechanical energy into each other for a wide range of applications. (1- x)Bi 0.5 Na 0.5 TiO 3 - x (0.5Ba 0.7 Ca 0.3 TiO 3 -0.5BaTi 0.8 Zr 0.2 O 3) (BNT- x (BCT-BZT)) lead-free piezoelectric ceramics were prepared through solid-state reaction methods. The structural, dielectric, field-induced strain and energy storage properties of the ceramics were investigated systematically by various characterization techniques. A large field-induced strain of 0.42% with negligible negative strain and large reverse piezoelectric coefficient of 547 pm/V are obtained in BNT-9(BCT-BZT) ceramics. A large recoverable energy storage of 3.49 J/cm3 under 360 kV/cm and high energy storage efficiency of 64.9% are achieved in the BNT-10(BCT-BZT) ceramics. It believes that the large strain with negligible negative strain is mainly due to the crossover of relaxor nonpolar state to ferroelectric polar state. We believe that the BNT- x (BCT-BZT) ceramics are favorable for the practical applications in the mobile electronic devices. [ABSTRACT FROM AUTHOR]

Dielectric energy-storage capacitors are of great importance for modern electronic technology and pulse power systems. However, the energy storage density (W rec) of dielectric capacitors is much lower than lithium batteries or supercapacitors, limiting the development of dielectric materials in cutting-edge energy storage systems. This study presents a single-phase BaTiO 3 -based high-entropy (BT-H) ceramic, which is synthesized using a conventional solid-state reaction method. It is found that the BT-H ceramic exhibits a remarkable energy storage performance, with a W rec of 5.18 J/cm3 and an ultrahigh η of 93.7% at 640 kV/cm electric field. Moreover, it also features wide temperature stability and excellent frequency stability. It is proposed that the introduction of high entropy enhances the random electric field and stress field, leading to lattice distortion and reduction of nanometer domain size, which in turn reduces remnant polarization and increases electric breakdown strength. This research provides a novel approach to improve the energy storage performance of ceramics through the high-entropy strategy. • High-entropy engineering could enhance the energy storage performance of dielectric capacitors. • An ultrahigh W rec of 5.18 J/cm3 and η of 93.7% at 640 kV/cm electric field were achieved in the BT-H (Mg) ceramics. • The BT-H ceramics exhibit remarkable energy storage performance stability. [ABSTRACT FROM AUTHOR]

• High-entropy engineering. • The activation energy. • Thermal stability. The utilization of a high entropy approach for the design of high-performance perovskite dielectric capacitors has been gaining much attention for the development of next-generation pulse power capacitors. Despite this, there are still challenges to further enhance their energy storage density and efficiency. To address this, a high-entropy strategy is proposed to significantly improve the energy storage characteristics of ceramics by increasing the configurational entropy and delaying saturation polarization. This approach has resulted in an ultra-high recoverable energy storage density (W rec) of 7.16 J/cm3 and a high efficiency (η) of 93.3 % for 0.8[0.65(Bi 0.5 Na 0.5)TiO 3 -0.35SrTiO 3)]-0.2[Ba(Zr 0.2 Ti 0.2 Sn 0.2 Hf 0.2 Nb 0.2)O 3 ] (abbreviated as 0.8BNST-0.2Ba(5 M)O) ceramic. The inclusion of Ba(5 M)O high entropy oxides has resulted in slender polarization–electric field hysteresis loops with delayed polarization saturation. The increase in atomic configuration entropy, degree of atomic disorder and lattice distortion due to the Ba(5 M)O high entropy oxides, has led to an increase in breakdown field, improved energy storage density and efficiency. Furthermore, excellent thermal stability (30–150 ℃), superior frequency stability (5–1000 Hz), and robust fatigue (100–105 cycles) endurance were achieved. The high entropy strategy has been demonstrated to be an effective method for the design of novel capacitors with superior energy storage performance. [ABSTRACT FROM AUTHOR]

The electrocaloric effect represents an adiabatic temperature change or isothermal entropy change upon the application or removal of an external electric field. However, the effect of the repetitive bipolar/unipolar electric field on the electrocaloric effect in ferroelectrics is not well understood. In this work, the electrocaloric effect after both bipolar and unipolar electrical cycling in Pb0.92La0.08Zr0.65Ti0.35O3 relaxor thin films has been indirectly evaluated using the Maxwell relationship. It was found that at room temperature, the electrocaloric temperature change ΔT under higher electric fields decreases gradually from a positive value to a negative one with the increase in the bipolar/unipolar fatigue cycle number. Intriguingly, around the Curie temperature, the positive ΔT of the film after bipolar/unipolar cycling was found to decrease under low or intermediate electric fields, while it remains almost unchanged under high electric fields. This behavior is attributed to the pinning effect of defects caused by phase decomposition during both bipolar and unipolar fatigue. Note that the increase in polarization by temperature induced domain depinning close to room temperature after the fatigue process is manifested by using the Maxwell relation indirectly. Our work further reveals the origin of both the electrocaloric effect and ferroelectric electrical fatigue and is important for the applications of practical electrocaloric refrigerators. [ABSTRACT FROM AUTHOR]

One of the key problems in the existing lead‐free piezoelectrics lies in how to further boost their dynamic piezoelectric responses, i.e., electrostrain and dynamic piezoelectric constants, in an effective and facile manner, making them comparable to those of widely used lead‐based counterparts. In this work, a new strategy is developed to largely improve the dynamic piezoelectric properties of lead‐free ferroelectrics using phase field simulations by combining the relaxor/ferroelectric crossover rendering potentially reversible electrostrain and the morphotropic phase boundary (MPB) providing easy paths of ferroelectric polarization rotations. Following the guidance of simulation results, Mn‐doped (Bi0.5Na0.5)TiO3–BaTiO3 lead‐free piezoelectric ceramics with relaxor/MPB crossover are synthesized. A large reversible electrostrain (Smax) of 0.55% with a promising piezoelectric constant d33* (Smax/Emax) of 917 pm V–1 at the designed relaxor/MPB crossover is obtained, outperforming almost all practical lead‐free counterparts when taking both electrostrain and dynamic piezoelectric constants into consideration. The strategy of utilizing relaxor/MPB crossover provides a new route for enhancing the dynamic piezoelectric responses in lead‐free ferroelectric perovskites. [ABSTRACT FROM AUTHOR]

In this work, the ternary system of potassium-sodium niobate has been designed to enhance the piezoelectric properties without sacrificing the Curie temperature greatly, and (0.97 - x)K0.48Na0.52NbO3-0.03Bi0.5(Na0.7K0.2Li0.1)0.5ZrO3-xB0.5Na0.5TiO3 ceramics have been prepared by the conventional solid-state method. The effect of B0.5Na0.5TiO3 content on the microstructure and electrical properties of the ceramics is studied. The phase diagram shows a phase boundary of the rhombohedral-tetragonal (R-T) phase coexistence in the composition range of 0.5% < x < 1.5%, and then an enhanced dielectric, ferroelectric, and piezoelectric behavior is obtained at such a phase boundary zone. The ceramic with x = 0.01 has an optimum electrical behavior of d33 ∼ 285 pC/N, kp ∼ 0.40, [variant_greek_epsilon]r ∼ 1235, tan δ ∼ 0.031, Pr ∼ 14.9 μC/cm2, and Ec ∼ 15.2 kV/cm, together with a high Curie temperature of ∼347 °C. The large d33 in such a ternary system is due to a composition-induced R-T phase transition and a higher &eh;rPr, and the thermal stability performance is strongly dependent on the phase structure. As a result, the design of the ternary system is an effective way to enhance the piezoelectric properties of potassium-sodium niobate materials. [ABSTRACT FROM AUTHOR]

Lead-free (0.70- x)BiFeO 3 -0.30BaTiO 3 - x AgNbO 3 +5‰mol CuO (abbreviated as BF-BT- x AN) ceramics were fabricated using a modified thermal quenching technique. BF-BT- x AN ceramics are of a perovskite structure with morphotropic phase boundary (MPB) and show strong relaxor properties. Remarkably, the high recoverable energy storage density of 2.11 J/cm3 is obtained for BF-BT- x AN with x = 0.14. For the x = 0.14 ceramics, its energy storage efficiency is as high as 84 % at relative low field of 195 kV/cm, together with an outstanding thermal stability in a broad temperature range from 25 °C to 150 °C. In addition, this ceramic maintains superior energy storage performance even after 8 × 104 electrical cycles due to its high densification after doping Ag 2 O and Nb 2 O 5. The result suggests that lead-free BF-BT- x AN ceramics may be promising candidate for dielectric energy storage application. [ABSTRACT FROM AUTHOR]

Piezoelectric actuators play an important role in modern electronic devices. In this work, 0.7Bi(1−x)SmxFeO3–0.3BaTiO3 lead-free piezo-ceramics are fabricated through the rapid thermal quenching technique for enhancing the electric-field-induced strain response. All the ceramic samples own a typical perovskite structure, and the morphotropic phase boundary can be achieved after Sm substitution. Additionally, a high TC of 403 °C and excellent ferroelectricity can be obtained at room temperature for the x = 0.03 composition, together with a large peak-to-peak strain value (∆S = 0.5%). Furthermore, a larger strain value ∆S of 0.45% at 150 °C can also be realized in 0.7Bi0.95Sm0.05FeO3–0.3BaTiO3 ceramic. Our results could further stimulate the investigations on lead-free ceramics for piezoelectric actuator applications. [ABSTRACT FROM AUTHOR]

Secondary electrocaloric effect (ECE) arising from piezoelectricity combined with crystal thermal expansion was often overlooked in ECE studies of ferroelectric ceramics. This work mainly evaluated the primary ECE (ΔT ECE) and secondary ECE (∆T 2) of eco-friendly BaSn x Ti 1 - x O 3 (BSnT100 x , 0 < x < 12%) ceramics near the tetragonal (T)-orthorhombic (O) transition. Intriguingly, a maximum overall ΔT ~ 0.85 K was obtained at the T-O transition (~300 K) of BSnT2 under an electric field of 2 kV/mm, with ∆T ECE and ∆T 2 amounting to ~0.75 K, ~0.1 K, respectively. This ECE result is ~40% superior than the larger ECE reported previously for BSnT system. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Thanks to its small hysteresis, large electrostrictive strain in relaxor ferroelectrics is superior than piezoelectric strain for applications in precision microactuators. Although relaxor ferroelectrics exhibit the largest electrostrictive strain in ceramics, the magnitude of the strain is limited to ∼0.20% at room temperature due to the large amount of non-ferroelectric defects existing in relaxors. In this work, we develop a relaxor with a morphotropic phase boundary (MPB) by doping a rhombohedral (R3m) ferroelectric BaZr 0.2 Ti 0.8 O 3 into a tetragonal (P4 mm) ferroelectric 0.89Bi 0.5 Na 0.5 TiO 3 -0.11BaTiO 3. A high electrostrictive strain of 0.27% is achieved at room temperature in the relaxor sample. Experimental results illustrate that the composition is near the MPB and exhibits the existence of nanodomains, favoring the achievement of high electrostrictive strain. Moreover, phase field simulations show that the high electrostrictive strain obtained at this composition originates from the low defect fields needed to induce relaxor as a result of small polarization anisotropy at the phase boundary as compared to conventional relaxors away from phase boundaries. Our work provides a new design strategy for the next generation of high-performance ferroelectric relaxors. Image, graphical abstract [ABSTRACT FROM AUTHOR]