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Although K0.5Na0.5NbO3 (KNN) possesses large maximum polarization and relatively high breakdown strength, the large remnant polarization constrains their practical applications as energy storage materials. In this work, through multi-element doping, (K0.5−0.5xNa0.5−0.5xBix)(Nb1−xSn0.2xZn0.6xTa0.2x)O3 relaxor ferroelectrics were prepared. As the superparaelectric states (SPE) were adjusted to room temperature, orthorhombic, tetragonal, and cubic phases coexisted, accompanied by the highly dynamic polar nanoregions (PNRs). In particular, a high recoverable energy storage density of 4.5 J/cm3 and an energy storage efficiency of 83% were achieved for the x = 0.125 ceramic, with the variations less than 11% and 4%, respectively, in the wide temperature range of 20–180 °C. These results demonstrate that the multiphase PNRs in the SPE state is an effective strategy for improving the energy storage performance of KNN-based ceramics. [ABSTRACT FROM AUTHOR]

Dielectric energy storage capacitors offer great potential in pulsed power devices due to the high power density and fast charging-discharging rate. Designing a host material with high field-induced polarization is of importance for developing dielectric energy storage materials via further composition modulation. In this paper, we compare the microstructure, dielectric, and ferroelectric properties as well as the energy storage performance of samples K1/2Bi1/2TiO3(KBT), 75KBT-25BiFeO3 (KBTF25), and 88KBT-12Bi0.85Nd0.15FeO3 (KBNTF12) in detail. It is found that, among three samples, sample KBNTF12 possesses the most complex local structure coexisting of a four-distortions with different polarities; meanwhile, sample KBNTF12 behaves as a strong relaxor, thus giving a high field-induced polarization. Besides, sample KBNTF12 realizes the highest electric breakdown strength Eb among three samples, which is resorted to the highest resistivity of grain boundary. Highest ΔP and Eb of sample KBNTF12 among three samples render it achieve ultrahigh stored energy density Ws of 6.94 J/cm3, high recoverable energy density Wr of 5.23 J/cm3, and high efficiency η of 75.4%. Our work suggests that 88KBT-12BNF binary composition be an optimal candidate for dielectric energy storage ceramics. [ABSTRACT FROM AUTHOR]

BiFeO 3 (BF) based ceramics are inspiring great interest in advanced pulsed power applications owing to their giant spontaneous polarization, meanwhile limited by the significant leakage current. In this work, Sr 0.7 Bi 0.2 TiO 3 (SBT) modified 0.7BiFeO 3 -0.3BaTiO 3 (BF-BT) ternary lead-free relaxor ferroelectric ceramics are investigated to elaborate the dielectric performances, including the impedance, relaxor behavior, ferroelectric and energy storage, and strain properties. The substitution of SBT induces a phase transition from an R 3 c to an average pseudo-cubic structure and forms a secondary phase at high dopants. Simultaneously, the resistivity, electrically homogeneous, and band gaps are increased significantly, related to the inhibition of oxygen vacancy formation. Besides, the ferroelectric long-range order is disrupted, which promotes the formation of local defect fields and polar nanoregions. The structural heterogeneity for the higher doped components leads to an increased relaxation behavior with an almost hysteresis-free polarization response to external electric fields. Excellent temperature-insensitive dielectric response and promising dielectric energy storage properties in low electric fields are achieved, respectively. These results indicate that the SBT modification is an effective route in regulating the dielectric performance of bismuth ferrite based relaxors. [ABSTRACT FROM AUTHOR]

Lead-free relaxor ferroelectric energy-storage ceramics based on Bi 0.5 Na 0.5 TiO 3 (BNT) systems are renowned for their exceptional properties, including a high P max (>40 μC/cm2) and Curie temperature (T c ∼ 320 °C). In the pursuit of further enhancing their energy storage characteristics, we have developed a novel series of ceramics, namely (1- x)(Bi 0.5 Na 0.5) 0.7 Sr 0.3 TiO 3 - x Ba 0.94 La 0.04 Zr 0.02 Ti 0.98 O 3 (x = 0, 0.1, 0.2, 0.3 and 0.4), abbreviated as (1- x)BNST- x BLZT, and assessed its structural and performance attributes. With the introduction of Ba 0.94 La 0.04 Zr 0.02 Ti 0.98 O 3 (BLZT), these ceramics retain their characteristic phase structure where tetragonal (T) and rhombohedral (R) phases coexist, effectively disrupting long-range ordered domains and augmenting their energy storage capabilities. Notably, we achieved a remarkable recoverable energy storage density (W rec) of 3.41 J/cm3 and an extraordinarily high energy storage efficiency (ƞ) of 87.33 % in ceramics with x = 0.3 under an electric field of 260 kV/cm. Furthermore, these ceramics exhibit excellent temperature stability (−2 °C ∼ 228 °C), robust cycle stability (106 cycles), a substantial discharge energy density (W d ∼ 0.93 J/cm3), impressive power density (P D ∼ 39.3 MW/cm3), and rapid transient discharge times (t 0.9 ∼ 0.14 μs). In summary, the 0.7BNST-0.3BLZT ceramic demonstrates high power density, rapid charge and discharge rates, and excellent temperature and cyclic stability, positioning it as a promising material for pulse power systems and harsh environments. [ABSTRACT FROM AUTHOR]

Excellent comprehensive energy storage performance is essential to ensure a favorable application prospect for high entropy dielectric capacitors. In this work, the energy storage performance of 0.8(Na 0.5 Li 0.5 NbO 3)-0.2(Sr 0.5 Bi 0.5)(Fe 0.5 Ti 0.25 Zr0.25)O 3 ceramics with high entropy was improved by incorporating various contents of MnO. The results show that with the addition of MnO, the relaxation behavior is enhanced, significantly improving energy storage performance, and a recoverable energy density of 7.93 J/cm³ and energy efficiency of 90.6 % is achieved for [0.8(Na 0.5 Li 0.5 NbO 3)-0.2(Sr 0.5 Bi 0.5)(Fe 0.5 Ti 0.25 Zr0.25)O 3 ]-0.05MnO under a 510 kV/cm electric field. Compared with non-MnO-doped ceramics, the size of the polar nanoregions (PNRs) is significantly reduced. It also shows remarkable stability to temperature and frequency. This study validates that integrating MnO effectively enhances the energy storage performance of high-entropy ceramics. [ABSTRACT FROM AUTHOR]

This paper reports an extensive investigation on the structural, dielectric, ferroelectric and pyroelectric properties of 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 (x = 0.0, 0.5, 0.6, 0.7) ceramics synthesized via conventional solid-state reaction (SSR) technique. X-ray diffraction data confirms the presence of pure perovskite phase. The variation of lattice parameters with strontium concentration in 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 ceramics were evaluated using the Rietveld refinement of the XRD data. The variation of dielectric permittivity with temperature (ε' ∼ T) shows the diffused phase transition and all the parameters related to the relaxor ferroelectrics (relaxation coefficient, activation energy and freezing temperature) were evaluated. The energy storage properties of the as-prepared ceramics were evaluated using the room temperature PE loop. Amongst the as-prepared ceramics, the composition with x = 0.5 possesses the highest energy storage density of 0.46 J/cm3 with an efficiency of 90 %. The temperature dependent P-E loops were used to study the electrocaloric effect (ECE). The ECE calculations were performed using in-direct method based on Maxwell's thermodynamic relations. A maximum adiabatic temperature change of 0.32 K is achieved at 268 K under a small applied electric field of 25 kV/cm for the ceramic with Sr content x = 0.5. Additionally, electrocaloric responsivity ξ max = 0.13 K mm/kV was also found for the studied ceramics. The above results show that the ceramic 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 with the composition x = 0.5 is a viable lead-free option for application in solid state refrigeration. [ABSTRACT FROM AUTHOR]

Bi 0.5 Na 0.5 TiO 3 -based ferroelectric ceramics have broad application prospects due to their excellent electrical properties and are considered to be one of the most promising functional materials to supersede lead-based materials. Here, 0.9Bi 0.5 Na 0.5 TiO 3 -0.1Bi 0.2 Sr 0.7 TiO 3 - x NaNbO 3 (BNT-BST- x NN) ternary lead-free ferroelectric ceramics were prepared, and the origin of their excellent dielectric properties was investigated in terms of phase boundary and domain structure. The introduction of NN led to a phase transition from the ferroelectric rhombohedral phase (R 3 c) to the relaxor tetragonal phase (P 4 bm), and the two phases coexisted in the BNT-BST- x NN ternary solid solution with x ranging from 0.06 to 0.2. Meanwhile, the macroscopic domain of BNT-BST was destroyed and replaced by highly active polar nano-regions (PNRs) of the P 4 bm phase, leading to an increase in local structural disorder and enhanced relaxor behavior. A dielectric constant (ε r) of ∼1765 (150 °C) with Δ ε / ε 150 °C less than 15 % over a broad range from 80 to 328 °C was achieved in the BNT-BST-0.15NN, and an excellent energy storage property (W rec = 3.3 J/cm3) was obtained under a low electric field (190 kV/cm). More specifically, the relationship among phase boundary, domain structure, and excellent electrical properties was achieved based on Rietveld refinements and the dielectric/ferroelectric characterizations. This work provides a deep insight into the phase evolution and its impact on the electrical properties of the BNT-based relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

A novel ferroelectric ceramic system, Pb(Ni 1/3 Nb 2/3)O 3 –Pb(Sc 1/2 Ta 1/2)O 3 –PbTiO 3 (PNN-PST-PT), with ultrahigh piezoelectricity and super electromechanical performance is developed. The microstructure and crystal structure of PNN-PST-PT ceramics, along with their electrical properties, were examined regarding PNN content. The results indicated that the room-temperature dielectric constant was considerably enhanced with PNN content increasing and the values of P r , P max , and E c steadily declining. The optimal performance was achieved in the 0.4PNN-0.235PST-0.365 PT composition with a high piezoelectric coefficient (d 33) of 1028 pC/N and an electromechanical coupling factor (k p) of 0.69. Strong piezoelectric response is attributed to the coexistence of R and T phases as well as the enhanced relaxation characteristics, which manifest as a specific polarization configuration resulting from the local structural distortion caused by the co-occupation of ions with different radii at the B-site. These suggest that PNN-PST-PT ceramics can be a desirable material for applications in high-quality piezosensors, actuators, etc. [ABSTRACT FROM AUTHOR]

In order to obtain large room-temperature electrocaloric effect (ECE) and wide operation temperature range simultaneously in lead-free ceramics, we proposed designing a relaxor ferroelectric with a Tm (the temperature at which the maximum dielectric permittivity is achieved) near-room temperature and glass addition. Based on this strategy, we designed and fabricated lead-free 0.76NaNbO3–0.24BaTiO3 (NN-24BT) ceramics with 1wt.% BaO–B2O3–SiO2 glass addition, which showed distinct relaxor ferroelectric characteristics with strongly diffused phase transition and a Tm near-room temperature. Based on a direct measurement method, a large ΔT (adiabatic temperature change) of 1.3 K was obtained at room temperature under a high field of 11.0 kV mm−1. Additionally, large ECE can be maintained (>0.6 K@6.1 kV mm−1) over a broad temperature range from 23 °C to 69 °C. Moreover, the ECE displayed excellent cyclic stability with a variation in ΔT below ±7% within 100 test cycles. The comprehensive ECE performance is significantly better than other lead-free ceramics. Our work provides a general and effective approach to designing lead-free, high-performance ECE ceramics, and the approach possesses the potential to be utilized to improve the ECE performance of other lead-free ferroelectric ceramic systems. [ABSTRACT FROM AUTHOR]

Background: The unique non-uniform polar nanoregions and complex phase structure near morphotropic phase boundaries (MPBs) in relaxor ferroelectric materials lead to rich microstructure changes (domain transition, phase transition) under external field stimulation. This not only results in the material with extremely high electromechanical properties, but also greatly affects their mechanical properties and stability. Objective: This study investigated the fundamental mechanical properties of the rhombohedral phase (R-phase) and tetragonal phase (T-phase) structures of the relaxor ferroelectric single crystal PMN-PT material using the nanoindentation with different shapes of indenters. Methods: The basic mechanical properties of the material were measured by nanoindentation, and the fracture caused by indentation was analyzed by scanning electron microscopy. Results: The elastic modulus of R-phase relaxed ferroelectric materials showed a significant dependence on the indentation depth, and the hardness of different phases (R, T-phase) materials all show obvious indentation size effects (ISE). Under the loading of the spherical indenter, both R and T phase materials exhibited a pop-in phenomenon caused by the transition from elastic to inelastic. Under the loading of the Berkovich indenter, the R and T phase materials showed different fracture characteristics of crack propagation response with the increase of the indentation depth. Conclusions: The result demonstrate that the mechanical properties of relaxor ferroelectric materials are significantly related to their phase structure, providing guidance for the design of load bearing and material selection in the practical application of related ferroelectric devices. [ABSTRACT FROM AUTHOR]

High-entropy dielectric capacitors have recently drawn increasing attention in the field of energy storage. In this study, NiO has been incorporated into [(Na 0.7 Bi 0.1) 0.8 Sm 0.02 Ca 0.02 Sr 0.02 Ba 0.02 ]Nb 0.8 Sb 0.1 Ta 0.1 O 3 -based ceramics. We applied the concept of high-entropy design to introduce cation vacancies at the A-site, enhancing conformational entropy. This approach led to the successful preparation of a novel type of energy-storage ceramics with an ABO 3 perovskite structure, denoted as (1- x)NBSCSBNST- x NiO (x = 0, 0.02, 0.04, & 0.06). We conducted a systematic study of the microstructural, dielectric, and ferroelectric characteristics, along with an exploration of the influence of the high-entropy strategy on their performance. The Δ S config increases with NiO doping, and the E b of the NBSCSBNST-0.02Ni sample exhibits a significant increase to 730 kV/cm from 550 kV/cm of NBSCSBNSTN. This enhancement is accompanied by a recoverable energy density (W rec) of 4.43 J/cm3 and an efficiency (η) of 75.9 %. As the content of NiO increases from x = 0 to x = 0.06, the phase transition diffusion behavior strengthens. Additionally, the permittivity (ε r) spectrum becomes more uniform, and the activation energy of the prepared ceramic samples increases from 1.03 eV to 1.76 eV. This effect suppresses the emergence of localized electric branching, eventually improving the breakdown strength of NBSCSBNST- x Ni ceramic materials. The obtained results indicate that the concept of high-entropy design to introduce cation vacancies at the A-site is an efficient approach to improve the energy storage characteristics of lead-free dielectric capacitors. [ABSTRACT FROM AUTHOR]

Studies on the piezoelectric materials capable of efficiently outputting high electrostrains at low electric fields are driven by the demand for precise actuation in a wide range of applications. Large electrostrains of piezoceramics in operation require high driving fields, which limits their practical application due to undesirable nonlinearities and high energy consumption. Herein, a strategy is developed to enhance the electrostrains of piezoceramics while maintaining low hysteresis by incorporating lead magnesium niobate relaxors into lead zirconate titanium at the morphotropic phase boundary. An ultrahigh inverse piezoelectric coefficient d 33 * of 1380 pm/V with a reduced hysteresis of 11.5% is achieved under a low electric field of 1 kV/mm, outperforming the major lead-based piezoelectric materials. In situ synchrotron X-ray diffraction and domain wall dynamics characterization with sub-microsecond temporal resolution reveal that the outstanding performances originate from facilitated domain wall movement, which in turn is due to reduced lattice distortion and miniaturized domain structures. These findings not only address the pending challenges of effective actuation under reduced driving conditions but also lay the foundation for a more systematic approach to exploring the origin of large electrostrains. The authors develop an application-oriented low-field actuating piezoceramic via relaxor substitution. Their in situ synchrotron XRD analysis along with domain wall dynamics characterization reveals the mechanisms of outstanding performance. [ABSTRACT FROM AUTHOR]

Ceramic capacitors have received great attention for use in pulse power systems owing to their ultra-fast charge–discharge rate, good temperature stability, and excellent fatigue resistance. However, the low energy storage density and low breakdown strength (BDS) of ceramic capacitors limit the practical applications of energy storage technologies. In this work, we present a series of relaxor ferroelectric ceramics (1−x) [0.94 Bi0.5Na0.5TiO3 –0.06BaTiO3]– x Sr0.7Bi0.2TiO3 (1-x BNT-BT- x SBT; x = 0, 0.20, 0.225, 0.25, 0.275 and 0.30) with improved energy storage performances by combining relaxor and antiferroelectric properties. XRD, Raman spectra, and SEM characterizations of BNT-BT-SBT ceramics revealed a rhombohedral–tetragonal phase, highly dynamic polar nanoregions, and a reduction in grain size with a homogeneous and dense microstructure, respectively. A high dielectric constant of 1654 at 1 kHz and low remnant polarization of 1.39 µC/cm2 were obtained with the addition of SBT for x = 0.275; these are beneficial for improving energy storage performance. The diffuse phase transition of these ceramics displays relaxor behavior, which is improved with SBT and confirmed by modified the Curie–Weiss law. The combining relaxor and antiferroelectric properties with fine grain size by the incorporation of SBT enables an enhanced maximum polarization of a minimized P-E loop, leading to an improved BDS. As a result, a high recoverable energy density Wrec of 1.02 J/cm3 and a high energy efficiency η of 75.98% at 89 kV/cm were achieved for an optimum composition of 0.725 [0.94BNT-0.06BT]-0.275 SBT. These results demonstrate that BNT-based relaxor ferroelectric ceramics are good candidates for next-generation ceramic capacitors and offer a potential strategy for exploiting novel high-performance ceramic materials. [ABSTRACT FROM AUTHOR]

Recently, high‐entropy perovskites have attracted considerable attention due to their diverse chemical composition and multifunctionality. In this study, the high‐entropy approach was employed in a (Bi0.4Na0.2K0.2Ba0.2)TiO3 matrix, and Nd3+ was introduced to enhance the configurational entropy and modify its dielectric and ferroelectric properties. Notably, despite Nd3+ doping, all samples maintained a tetragonal perovskite structure at room temperature. The configurational entropy increased with the Nd3+ concentration, consequently leading to a gradual decline in the ferroelectric properties along with the associated temperature (Tm) and maximum dielectric constant (εm). The P–E loops of the ceramics also became thinner as Pm and Pr decreased, resulting in a slow decrease in the recoverable energy density (Wrec) and a simultaneous increase in the energy storage efficiency (η). Especially, the energy storage performance reached its peak at an Nd3+ concentration of 12 mol%, exhibiting an energy storage efficiency of 85.8% and a recoverable energy storage density of 0.74 J/cm3 at a low electric field of 100 kV/cm. These results highlight the potential of this material for dielectric applications in low electric fields and contribute to the advancement of alternative high‐entropy energy storage perovskite ceramics. [ABSTRACT FROM AUTHOR]

(1- x)Na 0.5 Bi 0.5 TiO 3 - x BiFeO 3 (NBT-BFO) is a system with a composition-induced transition from relaxor to ferroelectric. Upon quenching, 0.4NBT-0.6BFO obtain a T d of 640 °C and d 33 of 56 pC/N. However, the quenching treatment also causes the reduction of resistivity, which is unfavorable for high-temperature piezoelectric ceramics. The aim of this study is to restrain quenching-induced decline of resistance in NBT-BFO ceramics by doping a small amount of BiAlO 3 (BA). For unquenched NBT-BFO-BA, with increasing BA content, the piezoelectric coefficient (d 33) decreases slightly, while the resistivity increases. After quenching, both d 33 and the depolarization temperature (T d) increase, but more importantly, the resistivity of quenched NBT-BFO-BA is comparable with that of the unquenched samples. This phenomenon is not observed in other quenched samples, and the reason is attributed to the defect dipoles caused by BA. Besides, the enhanced piezoelectric properties and the resistivity can be retained after annealing the quenched samples at 400 °C for 4 h. Thus, this work implies the potential application of NBT-BFO based piezoelectric ceramics at elevated temperatures. [ABSTRACT FROM AUTHOR]

The micrometer scale grain size and large remnant polarization of Bi 0.5 Na 0.5 TiO 3 (BNT) ferroelectric ceramics severely constrain the breakdown strength and energy efficiency, respectively, restricting their energy storage application despite their large polarization. Hereby, superior energy storage performance is reported by a synergistic strategy of introducing Sr 0.7 Bi 0.2 TiO 3 (SBT) relaxor ferroelectrics and a solution combustion synthesis (SCS) method. The BNT-SBT solid-solution ceramics are comparatively investigated by the two methods, conventional sintering (CS) and SCS. An ultrafine average grain size of ∼0.39 μm was obtained in the SCS-derived ceramic, and thus exhibits an ultra-high critical electric field of 548 kV/cm, and a high recoverable energy density of ∼5.69 J/cm3. Those key energy storage parameters are superior to those of the previous reported samples prepared by the CS method. Meanwhile, a high energy efficiency ∼90 %, a large power density of ∼130.44 MW/cm3 (at 320 kV/cm), and an ultrafast discharge time of ∼61.7 ns are also achieved. This study indicates that grain engineering combing with chemical design is an effective way to enhance the dielectric energy storage performance. [ABSTRACT FROM AUTHOR]

Dielectric capacitors harvest energy through an electrostatic storage process, which enables an ultrafast charging‐discharging rate and ultrahigh power density. However, achieving high energy density (Wrec) and efficiency (η) simultaneously, especially when preserving them across a wide frequency/temperature range or cycling numbers, remains challenging. In this work, by especially introducing NaTaO3 into the representative ferroelectric relaxor of Bi0.5K0.5TiO3‐Bi0.5Na0.5TiO3 and leveraging the mismatch between B‐site atoms, we proposed a method of enhancing local structural fluctuation to refine the polar configuration and to effectively improve its overall energy‐storage performances. As a consequence, the ceramic exhibits an ultrahigh Wrec of 15.0 J/cm3 and high η up to 80 %, along with a very wide frequency stability of 10–200 Hz and extensive cycling number up to 108. In‐depth local structure and chemical environment investigations, consisting of atom‐scale electron microscopy, neutron total scattering, and solid‐state nuclear magnetic resonance, reveal that the randomly distributed A/B‐site atom pairs emerge in the system, leading to the evident local structural fluctuations and concomitant polymorphic polar nanodomains. These key ingredients contribute to the large polarization, minimal hysteresis, and high breakdown strength, thereby promoting energy‐storage performances. This work opens a new path for designing high‐performance dielectric capacitors via manipulating local structural fluctuations. [ABSTRACT FROM AUTHOR]

High-performance piezoelectric materials are essential for diverse electromechanical devices, from actuators to sensors and transducers. Here, we synthesized Ce 2 O 3 -doped Pb(Mg 1/3 Nb 2/3)O 3 -0.29PbTiO 3 (x Ce-PMNT29) solid solutions via conventional solid-state methods. In the x = 2.5 % modified composition, we achieved a notable electrostrain-hysteresis trade-off, enhancing electrostrain (0.2 %), equivalent piezoelectric coefficient d 33 * (1701 pm V–1 at 3 kV cm–1), and reducing strain hysteresis to 8.1 %. Additionally , direct high-temperature piezoelectric characterizations revealed real-time variations in piezoelectric coefficient (d 33) and the actual depolarization temperature, with d 33 reaching 859 pC N−1 at 53 °C and planar electromechanical coupling coefficient (k p) exceeding 70 % within 30−85 °C. Leveraging x-ray diffraction (XRD) and piezoelectric force microscopy (PFM), we elucidated synergistic effects between complex nanodomains and local structural heterogeneity, enhancing piezoelectric activity. This study presents a promising approach for improving electromechanical performance and electrostrain in ferroelectrics, with significant potential for practical piezoelectric applications. [ABSTRACT FROM AUTHOR]

Owing to the ferroelectric-ferroelectric phase transition and macrodomains switching during the polarization process, it is challenging to achieve both large strain with low hysteresis in ferroelectric ceramics, which severely limits their usefulness for practical applications. In this work, an effective strategy of constructing multiple local polarization configurations is designed in lead-free (100-x)Na 0.52 K 0.48 Nb 0.9 Sb 0.1 O 3 -xBaZrO 3 (NKNS-xBZ) ceramics. The incorporation of BZ regulates both the polymorphic phase transition temperature and relaxor behavior of the NKNS matrix, leading to the coexistence of nanoscaled rhombohedral, orthorhombic, and tetragonal phases with ergodic relaxor at room temperature. Consequently, these polar nanodomains with multiple symmetries significantly decrease the polarization and strain hysteresis, leading to the high electrostrictive-like strain (∼0.2 %) and extremely low strain hysteresis (∼7.4 %) with good thermal stability (strain decrease < 10 % from 20 °C to 160 °C) at x = 4. This work provides effective guidance for obtaining high strain with low hysteresis in relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

Dielectric capacitors with high power density and fast charge-discharge speed play an essential role in the development of pulsed power systems. The increased demands for miniaturization and practicality of pulsed power equipment also necessitate the development of dielectric materials that possess high energy density while maintaining ultrahigh efficiency (η). In particular, ultrahigh efficiency signifies minimal energy loss, which is essential for practical applications but challenging to effectively mitigate. Here, we demonstrate a strategy of incorporating heterovalent elements into Ba(Zr0·1Ti0.9)O3, which contributes to achieving relaxor ferroelectric ceramics and reducing lattice strain, thereby improving the comprehensive energy storage performance. Finally, optimal energy storage performance is attained in 0.85Ba(Zr0·1Ti0.9)O3-0.15Bi(Zn2/3Ta1/3)O3 (BZT-0.15BiZnTa), with an ultrahigh η of 97.37% at 440 kV/cm (an advanced level in the lead-free ceramics) and an excellent recoverable energy storage density (Wrec) of 3.74 J/cm3. Notably, the BZT-0.15BiZnTa ceramics also exhibit exceptional temperature stability, maintaining fluctuations in Wrec within ∼10% and η consistently exceeding 90% across the wide temperature range of −55 °C to160 °C, and under a high electric field of 250 kV/cm. All these features demonstrate that the relaxor and lattice strain engineering strategies have been successful in achieving high-performance lead-free ceramics, paving the way for designing high-efficiency dielectric capacitors with a wide temperature range.

Knowledge of the statics and dynamics of ferroelectric domains is of immense importance since they are directly correlated with macroscopic polarization and strain. For the present work, piezoresponse force microscopy (PFM) is used to afford insight into field-induced phase transitions and local switching properties of a (1–2x)Na0.5Bi0.5TiO3–xBiFeO3–xPbTiO3 system for compositions, x = 0.01, 0.03, 0.05, and 0.07. Rietveld analysis of x-ray diffraction data reveals crystallization of the compound in single and dual phases in the chosen compositions. Upon the application of a local electric field, a phase transition from relaxor to normal ferroelectric (FE) is observed for all samples. A decrease in degree of non-ergodicity is realized within this composition range, which is found by analyzing the stability of field-induced ferroelectric domains. The field-induced FE domains for lower concentrations of x are found to be irreversible and a reversible nature was found for higher values of x. In addition, spatial variations of local switching parameters are investigated with the help of switching spectroscopic-PFM and a maximum local d 33 was found for compositions having dual phases. [ABSTRACT FROM AUTHOR]

Adding excessive metal oxide doping to a powder batch is a known way to compensate for the loss of volatile cation species during high temperature sintering. An important case in the piezoelectric ceramics is the bismuth oxide in the lead-free ferroelectric ceramic bismuth sodium titanate (BNT). Building from the earlier knowledge about excessive bismuth oxide's influences on the properties of BNT, we further note that varying the sintering temperature can both control the distribution of excessive Bi3+ and impact the relaxor/normal ferroelectric behaviors and corresponding phase transition. In addition to the nature of polarization, the sintering temperature also significantly manipulates the electrical conductivity. A hypothetical mechanism for the resistive grain boundary is proposed, based on inferences from electrical—microstructure—processing relations in 85% Bi0.5Na0.5TiO3-15% BaTiO3 with batched Bi2O3 excess and acceptor Mg2+ in a co-doped strategy. [ABSTRACT FROM AUTHOR]

The effect of calcination process on a phase evolution, a microstructure development and the piezoelectric properties were investigated in 0.75BiFeO 3 -0.25BaTiO 3 (0.75BF-0.25BT) ceramics. At the relatively low calcination temperatures of 600 °C–650 °C, a Bi 25 FeO 40 impurity phase was formed in addition to some unreacted raw materials and a perovskite phase. As the calcination temperature increased to the range of 700–900 °C, other intermediate phase BaBi 4 Ti 4 O 15 was formed concurrently with small amounts of unreacted BaCO 3 and perovskite matrix phase. At 950 °C a pure single perovskite phase of 0.75BF-0.25BT solid solution was observed. The sintered samples produced by using the raw powder calcined at a relatively low temperature of 600–900 °C showed a large fraction of pseudo-cubic relaxor phase (0.54–0.71 mass fraction) with the rest of a rhombohedral ferroelectric phase. They showed poor piezoelectric properties at sintering temperature below 1000 °C due to the nonuniform compositional distribution of the calcined powder. The homogeneous calcination at 950 °C for 2 h reduced greatly the optimum sintering temperature and significantly enhanced piezoelectric properties in the BF-BT ceramics. High Curie temperature as well as high piezoelectric properties were obtained at the sintering temperature as low as 920 °C: k p = 0.361, d 33 = 123 pC/N and T C = 653 °C in the 0.75BF-0.25BT ceramics and k p = 0.337, d 33 = 183 pC/N and T C = 525 °C in the 0.7BF-0.3BT ceramics. This low temperature sintering of the BF-BT ceramics by a homogeneous calcination could be applied to the fabrication of the lead-free multi-layer piezoelectric devices with inexpensive internal electrodes. [ABSTRACT FROM AUTHOR]

Electrocaloric refrigeration shows the merits of environmental safeguarding, large efficiency, easy combination, and miniaturization as a novel solid-state refrigeration technique. In this paper, Sn4+ is doped into the B site of BLNT ceramics. By adjusting the doping content, the T-C phase transition peak was successfully shifted to room temperature and promoted the formation of relaxor ferroelectrics, resulting in a wider operating temperature range (T span) and improved adiabatic temperature change (ΔT). A comprehensive study was conducted on the crystal structure, surface morphology, dielectric properties, ferroelectricity, and electrical properties of BLNTS ceramics with varying levels of Sn4+ doping. Wherein, when the doping amount is 5Sn, a maximum adiabatic temperature change value (ΔT max) of 1.14 K was obtained, and the temperature span (T span) reached 45 °C (T span is defined as ΔT ≥ 80 % ΔT max). This work proposes a high-performance environmentally friendly electrocaloric effect (ECE) material suitable for solid-state cooling applications. [ABSTRACT FROM AUTHOR]

In this work, (1− x)Bi 0 · 5 (Na 0 · 8 K 0.2) 0.5 TiO 3 - x SrTiO 3 ceramics were synthesized by the solid-phase method. The SrTiO 3 dopants cause a phase transition from of rhombohedral to tetragonal resulting in an enhanced strain of 0.49 % and normalized strain d 33 * of 817 p.m./V under 60 kV/cm at a doping amount of 0.04. The microstructure of BNKT-0.04ST, including cation displacements δ Ti-Bi/Na and the tilt of oxygen octahedron are researched by aberration corrected scanning transmission electron microscope (AC-STEM). The fast Fourier transform (FFT) of the annular dark field (ADF) STEM pattern along [110] axis reveals the 1/2 (ooo) superlattice reflection spots due to anti-phase a − a − a − the tilt of oxygen octahedron. The cation displacement vector maps based on the ADF STEM and the enhanced annular bright fielde (eABF) STEM images along the [100] axis show the rhombohedral and tetragonal phase nanodomains, and the displacement decreases gradually from the inside of the nanodomains towards the domain walls. The tilt of oxygen octahedron has the same variation tendency indicating the regional coherence. Due to the flexible nanodomains based on the cooperative effect of the tilt of oxygen octahedron and cation displacement, which is thought to be the origin of the relaxor characteristic and strain. [ABSTRACT FROM AUTHOR]

This study presents "K0.5Na0.5NbO3-based" Pb-free smart material 0.80(K0.5Na0.5NbO3)–0.20(Ba0.9Sr0.1TiO3) (KBST20) as exhibiting zero thermal expansion (ZTE) at low temperatures (T ≤ 100 K) with long-range cubic symmetry stable over a wide temperature range (9 K ≤ T ≤ 500 K). The linear coefficient of the thermal expansion (αl) obtained from temperature-dependent neutron diffraction data is in the range of 0.255–5.75 × 10−6 K–1 (9–500 K), which is rarely observed for Pb-free materials possessing long-range cubic symmetry. The temperature-dependent dielectric data of KBST20 exhibits a strong relaxational behavior with high frequency dispersion (Δ T ≈ 27 K), suggesting the presence of polar phased regions known as polar nano regions. The ZTE has been attributed to enhanced correlations among PNRs exhibiting ferroelectrostriction. Furthermore, temperature-dependent Raman scattering data reveal polar monoclinic distortion at short ranges rather than cubic symmetry at long ranges. In addition, the intensity of Raman modes increases with the decrease in temperature, suggesting enhancement of the polar phase at low temperatures, which consequently leads to zero thermal expansion in KBST20. [ABSTRACT FROM AUTHOR]

In the current study, the incorporation of Ba(Sn0.70Nb0.24)O3 (BSN) effectively modifies the phase boundary of the 0.8(Bi0.50Na0.50)TiO3‐0.2(Bi0.50K0.50)TiO3 (BNKT) lead‐free ceramic material, inducing enhanced electrostrain properties at room temperature, particularly results in a "bud‐like" strain profile without negative strain. A comprehensive investigation has been conducted into the microstructure, electrical properties, and electrostrain properties of the above‐mentioned ceramics. The addition of BSN was observed to be well incorporated into the BNKT crystal structure, forming a single perovskite structure according to the X‐ray diffraction pattern. With the increase in BSN solid solution content, the temperature at which the transition from ferroelectric to the relaxor phase occurs shifted from 88.1°C to beneath room temperature (30°C). Specifically, the BNKT‐0.0075BSN ceramic demonstrated a positive strain response of 0.459% along with a large signal piezoelectric coefficient (d33*) of 643 pm/V. Additionally, the strain hysteresis of the BNKT‐0.0175BSN ceramics was only about 3% at 120°C. These experimental findings suggest that BNKT‐xBSN ceramics could be strong contenders for actuators and sensors, presenting promising opportunities for lead‐free ceramic actuator applications. [ABSTRACT FROM AUTHOR]

Dielectric capacitors, which can achieve tremendous power density and ultrafast charge/discharge speed, are crucial components for high power equipment. Yet, the synchronous achievement in high recoverable energy density (Wrec) and high efficiency (η) is a long‐term difficulty for dielectric ceramics. Herein, the (0.85 − x)NaNbO3–0.15BaTiO3–xBi(Mg1/3Ta2/3)O3 (NN–BT–xBMT) relaxor ferroelectric ceramics were proposed and studied. The doping of BMT was conducive to promoting the microstructure and bandgap and improving the dielectric relaxation properties of NN–BT ceramics. Finally, the sample of x = 0.10 presented a high Wrec of 5.9 J/cm3 and a high η of 90% simultaneously. In addition, the sample also exhibited superb charge/discharge performances with large power density (PD = 137 MW/cm3) and fast charge/discharge speed (t0.9 = 39 ns). The above results reveal that the NaNbO3‐based ceramics could serve as potential alternatives for advanced dielectric capacitors. [ABSTRACT FROM AUTHOR]

NaNbO 3 ceramics have broad application prospects in ultra-high power electronic systems, electromagnetic pulses, and other applications. In this study, (1- y)[(1- x)NaNbO 3 - x SmMg 0.5 Zr 0.5 O 3 ]- y (Bi 0.5 Na 0.5) 0.7 Sr 0.3 TiO 3 (x = 0.06, 0.08 and 0.10)(y = 0.30, 0.35, 0.40 and 0.45) ceramics were fabricated. The effects of the incorporation of SmMg 0.5 Zr 0.5 O 3 (SMZ) and (Bi 0.5 Na 0.5) 0.7 Sr 0.3 TiO 3 (BNST) on the energy storage performance, impedance, actual charge and discharge capacity, phase structure and microstructure of the ceramic samples were analyzed. Finally, when x = 0.08, and y = 0.35, the recoverable energy storage density of the sample was 5.8 J/cm3 and a high energy storage efficiency of 88 % was obtained at 545 kV/cm. In addition, the ceramic maintains a stable actual charge and discharge capacity and an extremely fast discharge time (16.1 ns) in a wide temperature range (20–160 °C). These excellent energy-storage performances may be due to the fine grain size and large relaxation and activation energies. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing novel lead‐free ferroelectric materials is crucial for next‐generation microelectronic technologies that are energy efficient and environment friendly. However, materials discovery and property optimization are typically time‐consuming due to the limited throughput of traditional synthesis methods. In this work, we use a high‐throughput combinatorial synthesis approach to fabricate lead‐free ferroelectric superlattices and solid solutions of (Ba0.7Ca0.3)TiO3 (BCT) and Ba(Zr0.2Ti0.8)O3 (BZT) phases with continuous variation of composition and layer thickness. High‐resolution x‐ray diffraction (XRD) and analytical scanning transmission electron microscopy (STEM) demonstrate high film quality and well‐controlled compositional gradients. Ferroelectric and dielectric property measurements identify the "optimal property point" achieved at the composition of 48BZT–52BCT. Displacement vector maps reveal that ferroelectric domain sizes are tunable by varying {BCT–BZT}N superlattice geometry. This high‐throughput synthesis approach can be applied to many other material systems to expedite new materials discovery and properties optimization, allowing for the exploration of a large area of phase space within a single growth. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectrics are highly desired for pulse-power dielectric capacitors, however it has become a bottleneck that substantial enhancements of energy density generally sacrifice energy efficiency under superhigh fields. Here, we demonstrate a novel concept of highly polarizable concentrated dipole glass in delicately-designed high-entropy (Bi1/3Ba1/3Na1/3)(Fe2/9Ti5/9Nb2/9)O3 ceramic achieved via substitution of multiple heterovalent ferroelectric-active principal cation species on equivalent lattice sites. The atomic-scaled polar heterogeneity of dipoles with different polar vectors between adjacent unit cells enables diffuse reorientation process but disables appreciable growth with electric fields. These unique features cause superior recoverable energy density of ~15.9 J cm−3 and efficiency of ~93.3% in bulk ceramics. We also extend the highly polarizable concentrated dipole glass to the prototype multilayer ceramic capacitor, which exhibits record-breaking recoverable energy density of ~26.3 J cm−3 and efficiency of ~92.4% with excellent temperature and cycle stability. This research presents a distinctive approach for designing high-performance energy-storage dielectric capacitors. The authors introduce the concept of highly polarizable concentrated dipole glass, involving the reduction of polar order scale from the nanoscaled polar nanodomains in traditional relaxor ferroelectrics to atomic-scale individual dipoles. [ABSTRACT FROM AUTHOR]

Eco-friendly (0.73- x)Bi 1.05 FeO 3 - x LiNbO 3 -0.27BaTiO 3 ternary ceramics were designed and prepared via a solid-state sintering route. Based on the X-ray diffraction results and Rietveld refinement, it was found that the structure of the ceramics transformed from rhombohedral to tetragonal symmetry with the addition of LiNbO 3 , and at x = 0.003, there existed a morphotropic phase boundary separating the two phases. Near the phase boundary, the largest values were achieved for the piezoelectric constant d 33 and planar electromechanical coupling coefficient k p , being 180 pC/N and 0.27, respectively. Due to the addition of LiNbO 3 , the grain size tended to become smaller. Additionally, the ceramics were transitioned from normal to relaxor ferroelectrics with increasing x. Despite the fact that the LiNbO 3 addition would result in a gradual decrease of Curie temperature, a relatively high Curie temperature (535 °C) was still maintained at x = 0.003, the phase boundary composition, which also showed good temperature stability of piezoelectric properties. These experimental results can provide a reference for the practical applications of high-temperature lead-free ceramics. [ABSTRACT FROM AUTHOR]

The synthesis of Bi 0.5 (Na 0.81 K 0.19) 0.5 Ti 1− x Nb x O 3 (BNKT- x Nb) lead-free piezoelectric ceramics via the traditional solid-state method, with varying x from 0.5 % to 4.0 %, is reported. Investigating the influence of Nb5+ ions on dielectric, ferroelectric, and electrostrain properties, alongside assessing the temperature stability of electrical properties, unveiled a notable electrostrain of 0.46 % at room temperature under 80 kV/cm for the 2.0 mol.% Nb5+ doped composition. The incorporation of Nb5+ prompted a transition from the ferroelectric to the relaxor phase, facilitating reversible induction into the ferroelectric phase under an external electric field, leading to the observed large electrostrain. Leveraging the first-order reversal curve (FORC) approach, a detailed analysis of the dynamic response process of different phase structures under the influence of the external electric field was conducted. This analysis elucidated that the continuous polarization response near the boundary of ferroelectric and relaxor phases, induced by the external electric field, primarily drives strain enhancement. These findings underscore the effective modulation of phase structure through Nb5+ doping, offering significant advancements in strain properties. This study opens avenues for the utilization of the material in micro actuators and provides valuable insights for the development of high-performance lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

The high strain hysteresis has impeded lead-free piezoelectric ceramics to replace lead zirconate titanate ceramics applied in actuators. In this study, we report a significant advancement with the synthesis of a novel BiFeO 3 -BaTiO 3 -(Ba 0.6 Sr 0.4)TiO 3 (BF-BT-BST) system. The optimal composition has demonstrated a remarkable strain of 0.42 % coupled with a notably low hysteresis of 21 %. It is found that the incorporation of BST into BF-BT facilitates the transition from the rhombohedral phase to the pseudo-cubic phase, which in turn significantly enhances the relaxor ferroelectric characteristics of the ceramic. Through adjusting the composition proportion of BST, a unique ferroelectric domain structure is established for the BF-BT-0.04BST ceramic, where polar nanoregions (PNRs) are surrounded by ferroelectric macrodomains. The domain structure enables the ceramic to have the ability to respond the external electric field quickly compared to the PNRs for typical relaxor composition, thereby leading to large strain and low hysteresis simultaneously. Hence, it is inferred that the ferroelectric macrodomains simplify the response process of the PNRs under electric field. This study provides an efficient strategy to break through the bottleneck of large strain hysteresis for BF-BT ceramic, and gives a deep comprehension for the improvement of the strain characteristics. [ABSTRACT FROM AUTHOR]

NaNbO3‐based (NN) energy storage ceramics are known for exhibiting high maximum polarization (Pmax) and large recoverable energy density (Wrec). However, the huge energy loss density (Wloss) has been a limiting factor in improving energy storage performance. Therefore, a ternary system was designed to achieve both huge Wrec and efficiency (η). The combination of 0.35Bi(Zn0.5Ti0.5)O3–0.65BaTiO3 (BZTBT) was chosen to reduce grain size and disrupt the long‐range ordered domains, thereby inducing the polar‐nano‐regions to mitigate Wloss. The optimal performance was achieved with the 0.75NaNbO3–0.25(0.35Bi(Zn0.5Ti0.5)O3–0.65BaTiO3) (0.75NN–0.25BZTBT) ceramic, which exhibited a high Wrec = 2.68 J/cm3 and superior η = 82.7% under 310 kV/cm. Remarkably, the 0.75NN–0.25BZTBT ceramic displayed an exceptionally fast discharge time to 90%, t0.9 = 88 ns, coupled with a huge energy density Wd = 0.95 J/cm3. This study demonstrates the significant potential of 0.75NN–0.25BZTBT ceramic in the realm of energy storage and rapid charge–discharge applications. [ABSTRACT FROM AUTHOR]

Heterovalent ion doping has influenced the further development of piezoelectric applications. Pr3+ doping in relaxor ferroelectrics is rarely focused on piezoelectric performance enhancement. 0.51 Pb(Ni 1/3 Nb 2/3)O 3 -0.49 Pb(Hf 0.3 Ti 0.7)O 3 (PNN-49PHT) ceramics with Pr3+ doping ceramics were designed and fabricated by a two-step precursor method. Excellent dielectric diffusion coefficient (γ) of 1.96 was achieved at the low Pr3+ doping concentration of 0.2 %. Increased relaxation enhanced the nanoscale domains formation, resulting in a giant strain response (d* 33) of 1400 pm/V at 10 kV/cm, and a total strain (S tol) of 0.27 % at 20 kV/cm. Structural refinement unveiled that the high piezoelectricity originated from the mainly substitution of Pr3+ for Pb2+ at the A-site, inducing lattice distortion and phase transitions. Local domain switching and long-range ordered destruction were investigated by piezoresponse force microscopy (PFM) and Scanning Electron Microscopy (SEM). These findings contribute to the advancement of piezoelectric devices and provide valuable insights for the design and optimization of high-performance piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

The trade-off between electrostrain and strain hysteresis for piezo/ferroelectric materials largely restrains the development of high precision actuators and remains unresolved over the past few decades. Here, a simple composition of (Bi0.5Na0.5)1-x/100Srx/100TiO3 in the ergodic relaxor state is collaboratively designed through the segregated domain structure with the ferroelectric core, local polarization heterogeneity, and defect engineering. The ferroelectric core can act as a seed to facilitate the field-induced nonpolar-to-polar transition. Together with the internal bias field caused by defect dipoles and adjusted through electric field cycling and heat treatment technology, a giant unipolar strain of 1.03% is achieved in the x = 30 ceramic with a low hysteresis of 27%, while the electric-field-independent large-signal piezoelectric strain coefficient of ~1000 pm/V and ultralow hysteresis of <10% can be obtained in the x = 35 ceramic. Intriguingly, the low-hysteresis high strain also exhibits near-zero remnant strain, excellent temperature and cycling stability. The development of precision piezo/ferroelectric actuators is hindered by the trade-off between electrostrain and strain hysteresis. Here, the authors report ferroelectric cores embedded into ergodic relaxor phase shells, showing giant unipolar strain and low hysteresis. [ABSTRACT FROM AUTHOR]

As the demand for miniaturization of electronic devices increases, ceramics with an ABO3 structure require further improvement of the dielectric constant with high permittivity. In the present work, Ba1−1.5xBixTiO3 (BB100xT, x = 0.0025, 0.005, 0.0075, 0.01) ceramics were prepared via a solid-state reaction process. The effect of Bi doping on dielectric properties of lead-free relaxor ferroelectric BaTiO3-based ceramics was studied. The results showed that both colossal permittivity (37,174) and a temperature stability of TCC ≤ ±15% (−27–141 °C) were achieved in BB100xT ceramics at x = 0.5%. The A-site donor doping produces A-site vacancies, a larger space for Ti4+, and fluctuation of the component, which is partially responsible for the high permittivity and responsible for the temperature stability. Meanwhile, the contribution of defect dipoles, and IBLC and SBLC effects to polarization leads to the colossal permittivity. The formation of a liquid phase during sintering promotes mass transfer when the doping content is higher than 0.5%. This work benefits the exploration of novel multilayer ceramic capacitors with colossal permittivity and temperature stability via defect engineering. [ABSTRACT FROM AUTHOR]

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For an ideal electrostatic energy storage dielectric capacitor, the pursuit of simultaneously high energy density and efficiency presents a formidable challenge. Typically, under an applied electric field, an increase in energy density is usually accompanied with a deteriorated energy storage efficiency due to the escalated hysteretic loss, which is harmful to the reliability of the capacitor. Thus, a well‐balanced performance of improved energy density and maintained high efficiency is highly demanded. In this work, a structure with amorphous phases embedded in polycrystalline nanograins using the entropy tactic, leading to a higher transport barrier of carrier is constructed. Hence, the hysteretic loss is largely suppressed at a high electric field and the high polarization is still sustained in the high‐entropy film. Consequently, an ultrahigh energy density of 139.5 J cm−3 with a high efficiency of 87.9%, and a high figure of merit of 1153 are simultaneously achieved in the high‐entropy Ba2Bi4Ti5O18‐based relaxor ferroelectric. This work offers a promising avenue in materials structure design for advanced high‐power energy storage applications. [ABSTRACT FROM AUTHOR]

Re-poling of unexpected partially depoled piezoelectric materials conventionally needs to be first fully depoled through annealing above their Curie temperature to revive piezoelectric performances. Here, we investigated de-poling and re-poling of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals under electric fields at room temperature. We found that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to successfully depolarize poled crystals at room temperature. We also demonstrated a reversible polarization switching process with a relaxor-PbTiO3 single crystal ultrasound transducer without device performance degradations. This experimental observation is supported by phase-field simulation, showing that alternating current electric fields can readily induce de-poling at room temperature, while direct current electric fields induce a transient depoled state only within an uncontrollable short period of time. The findings suggest new strategies for unprecedented in-device tailoring of the polarization states of ferroelectric materials. The authors find that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to depolarize poled relaxor-PbTiO3 single crystals at room temperature, without conventional heat treatment. [ABSTRACT FROM AUTHOR]

As the two typical basic binary solid solutions of the relaxor-PbTiO3 family, Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) has been widely investigated, whereas Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) has not. Here, 1.5 mol% Sm-doped (1 − x)Pb(Ni1/3Nb2/3)O3–xPbTiO3, (1 − x)PNN–xPT:0.015Sm with x = 0.33–0.39, ceramics have been prepared and the chemical composition-induced evolution of crystal structure, domain, and electrical properties investigated systematically. With increasing PT content, evolution of the rhombohedral–tetragonal structure was observed. A rhombohedral–tetragonal morphotropic phase boundary occurred around x = 0.36–0.37, which showed a peak piezoelectric property with piezoelectric constant d33 = 531 pC N−1 and planar electromechanical coupling factor kp = 0.37 at room temperature. At the same time, the x = 0.36 composition showed improved ferroelectric behavior with remanent polarization Pr = 13.4 μC cm−2 and coercive field Ec = 3.2 kV cm−1. Interestingly, different from its PMN-PT counterpart, there is no temperature-driven phase transition between room temperature and the Curie temperature for (1 − x)PNN–xPT:0.015Sm. These parameters indicated that the PNN-PT system is worthy of more attention and is a promising platform for further development of high-performance piezo/ferroelectric materials. [ABSTRACT FROM AUTHOR]

As the two typical basic binary solid solutions of the relaxor-PbTiO3 family, Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) has been widely investigated, whereas Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) has not. Here, 1.5 mol% Sm-doped (1 − x)Pb(Ni1/3Nb2/3)O3–xPbTiO3, (1 − x)PNN–xPT:0.015Sm with x = 0.33–0.39, ceramics have been prepared and the chemical composition-induced evolution of crystal structure, domain, and electrical properties investigated systematically. With increasing PT content, evolution of the rhombohedral–tetragonal structure was observed. A rhombohedral–tetragonal morphotropic phase boundary occurred around x = 0.36–0.37, which showed a peak piezoelectric property with piezoelectric constant d33 = 531 pC N−1 and planar electromechanical coupling factor kp = 0.37 at room temperature. At the same time, the x = 0.36 composition showed improved ferroelectric behavior with remanent polarization Pr = 13.4 μC cm−2 and coercive field Ec = 3.2 kV cm−1. Interestingly, different from its PMN-PT counterpart, there is no temperature-driven phase transition between room temperature and the Curie temperature for (1 − x)PNN–xPT:0.015Sm. These parameters indicated that the PNN-PT system is worthy of more attention and is a promising platform for further development of high-performance piezo/ferroelectric materials. [ABSTRACT FROM AUTHOR]

The pursuit of lead-free ceramic capacitors with superior energy storage properties has garnered increasing attention. Herein, 0.7Bi 0.5 Na 0.5 TiO 3 -0.3SrTiO 3 - x La (BNT-ST- x La) ceramics were synthesized via citrate combustion technology. The results show that La doped BNT-ST induces dielectric relaxation behavior and promotes the formation of nanoscale domains, which has been confirmed by PFM and TEM, and slim hysteresis loops are realized as addition of La. The recoverable energy-storage density (W re of 2.05 J/cm3) and efficiency (η of 82 %) are obtained in 4 mol% La doped ceramic under relatively low electric field of 170 kV/cm. The energy-storage performances of the ceramics show excellent frequency stability (W re varies <1.9 % and η varies <3.1 % at 5 Hz–100 Hz) and thermal stability (W re varies <1 % and η varies <6.1 % within 23 °C to 73 °C). It is revealed that the introduction of La results in the formation of nanodomains with currently improved energy storage properties. [ABSTRACT FROM AUTHOR]

With the increasing demand for high energy density and reliable dielectric capacitors in the field of power electronics, the research and manufacture of ceramic capacitor materials face significant challenges. At present, the traditional design ideas of dielectric ceramic materials have gradually formalized, and the system is complex and similar, whether it can design dielectric ceramic materials with high performance from a new viewpoint and explore the underlying mechanism remains a great challenge. This paper is based on ceramic capacitors with high energy storage performance, a series of high-entropy perovskite oxide ceramics designed by the concept of "entropy engineering" in the past five years are reviewed. The relationship between microstructure and macroscopic energy storage performance of materials is discussed based on the four effects of high-entropy ceramics. We predict that "entropy engineering" will be a successful strategy to break through the bottleneck of dielectric materials with high energy storage performance. This review guides the custom design of composition-structure-properties in high-entropy energy storage ceramics. [ABSTRACT FROM AUTHOR]

The thermal depolarization behavior of PMN-PT-5BZT relaxor ferroelectric ceramics was studied, and the depolarization mechanism was discussed from the perspective of domain structure transitions. In addition to the transition from MPB structure at room temperature to cubic phase at high temperature, the structure symmetry of PMN-PT-5BZT ceramics has no obvious change with increasing temperature. However, the ceramic had experienced a transition process from ferroelectric state to nonergodic relaxor state, and then to ergodic relaxor state. The results of temperature dependence of ferroelectric properties showed that the depolarization temperature T d corresponds to the transition temperature T F-NR from ferroelectric state to nonergodic relaxor state, and there is an obvious dielectric abnormal peak at this temperature, which is mainly due to the depolarization behavior caused by the decrease of macrodomain size and the beginning of transition to nanodomains. [ABSTRACT FROM AUTHOR]

Electrocaloric refrigeration which is environmentally benign has attracted considerable attention. In distinction to ferroelectric materials, which exhibit an extremely high positive electrocaloric effect near the Curie temperature, antiferroelectric materials represented by PbZrO3 have a specific negative electrocaloric effect, i.e., electric field decreases the temperature of the materials. However, the explanation of the microscopic mechanism of the negative electrocaloric effect is still unclear, and further research is still needed to provide a theoretical basis for the negative electrocaloric effect enhancement. Herein, the antiferroelectric phase-field model has been proposed to design polar boundaries enhancing antiferroelectric negative electrocaloric performance in PbZrO3-based materials. Based on this, we have simulated the polarization response and domain switching process of the temperature and electric field-induced antiferroelectric—ferroelectric phase transition. It is shown that the temperature range tends to increase as the density of polar boundaries increases from the antiferroelectric stripe domain, polymorphic domain to the nanodomain. Among them, the peak adiabatic temperature change of antiferroelectric nanodomains can reach −13.05 K at 84 kV/cm, and a wide temperature range of about 75 K can be realized at 42 kV/cm. We expect these discoveries to spur further interest in the potential applications of antiferroelectric materials for next-generation refrigeration devices. [ABSTRACT FROM AUTHOR]

The amelioration of atomically thin ferroelectric materials is imperative for next‐generation outperformed two‐dimensional (2D) electronics, which is elusive by their bulk counterparts. These remarkable materials' ferroelectric and piezoelectric features are the fundamental urges in optoelectronics, electronics, and energy harvesting. In this work, 2D ferroelectric Bi2O2Se flakes have been synthesized using a modified chemical vapor deposition technique. The 6 nm thick Bi2O2Se flake provides a robust ferroelectric switching under an applied voltage of ±10 V by piezoresponse force microscopy, further confirmed by first principles. Leveraging the successful growth, the high‐quality Bi2O2Se flakes permit the fabrication of a field‐effect transistor (FET) with state‐of‐the‐art performance. The FET device rewards a high current on–off ratio of 108 and field effect mobility of almost 131 cm2 V−1 s−1, owing to the small carrier effective mass of 0.2 m0. Combined, the electric field‐induced local polarization of ferroelectric switching and unprecedented device performance of Bi2O2Se semiconductors are certified for their utilization in advanced nanoelectronics and miniaturization of multifunctional devices with multifunctionalities. [ABSTRACT FROM AUTHOR]

In this work, the electrocaloric effect (ECE) and electrocaloric strength (ΔT/E) were measured and thermal and dielectric studies were performed on Pb-modified BaTiO3 (BPT). The saturated hysteresis loops and normal ferroelectric behavior of the ferroelectric ceramics allow the utilization of the indirect method to estimate the electrocaloric properties. The electrocaloric measurements were performed under high (18 kV/cm) versus low (8 kV/cm) electric field conditions. These conditions were chosen to notice and then eliminate an artificial negative electrocaloric effect in the tested ceramics. At the same time, relatively high values of positive electrocaloric temperature change ΔT ( ~   2.19   K ) and electrocaloric strength ΔT/E ( ~ 0.27–0.11 K · cm/kV) were obtained. [ABSTRACT FROM AUTHOR]