Polar Nanoregions Research Articles

Ultra-high electrostrain in flux-grown (Bi0.5Na0.5)TiO3-0.06BaTiO3-0.03(K0.5Na0.5)NbO3 single crystals around the nonergodic/ergodic crossover region

In this study, we successfully grew large-sized single crystals (12 × 11 × 8 mm³) of 0.91Bi0.5Na0.5TiO3-0.06BaTiO3-0.03(K0.5Na0.5)NbO3 (BNT-6BT-3KNN) with a <100>c orientation using the flux growth method. This marks the first instance of achieving such crystals. The single crystals display double hysteresis loops, featuring a maximum polarization of ∼64.6 μC/cm2. Capitalizing on the nonergodic/ergodic boundary, the single crystals exhibit a substantial strain (Sm) of 0.91% at the maximum electric field of 20 kV/cm and an exceptionally high inverse piezoelectric coefficient d33* of 4550 pm/V. The creation of long-range domains from needle-like nanodomains and polar-nano regions under the application of an electric field was confirmed through bright-field transmission electron microscopy and piezoresponse force microscopy analyses. The phase diagram for BNT-6BT-3KNN single crystals was constructed by analyzing the temperature dependence of dielectric, ferroelectric, and electrostrain behaviors.

Dual-template textured BNT-based ceramics with ultra-low electrostrain hysteresis

The biggest difficulty facing the grain growth (TGG) method is the compatibility between template and ceramic matrix. Different templates show great differences in texture degree. Consider the limitation of conventional single-template method, the strategy of dual-template textured ceramics and sintering aids were introduced in this work. With the addition of ST and NN templates into BNT system, the texture degree is higher than 90% and the electrostrain reach ∼ 0.5% with ultra-low hysteresis ∼ 15%, which cannot be realized in single template textured ceramics. The two templates and sintering aids play different roles in grain orientation growth, which is important for the compatibility among matrix and templates, leading to unique microstructures. Sintering processes clearly reveal the growth mechanism of textured ceramics under the joint action of two templates, and of course, the sintering aids are also indispensable. Regard to domain structure, the polar nanoregions can respond quickly under electric field, providing assistance for the realization of ultra-low hysteresis.

Ferroelectric behavior arising from polar topologies in epitaxially strained SrTiO3-δ ultrathin films

In this work, we show that epitaxially strained SrTiO3-δ thin films, grown by ion-beam sputtering onto (001)Nb:SrTiO3 substrates, exhibit a ferroelectric behavior. At the atomic-scale, through high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images, it was possible to identify the presence of polar nanoregions with non-trivial polar topological structures in the SrTiO3-δ film, which are induced through oxygen vacancies. To further confirm the presence of strained regions with a polar structure, Raman spectroscopy and high-resolution X-ray diffraction were employed and it was possible to confirm the presence of a tetragonal structure in the SrTiO3-δ film, with a tetragonality ratio (c/a) of 1.005. Scanning probe microscopy and macroscopic polarization-electric field hysteresis loops show ferroelectric behavior with maximum polarization of ∼1.5 μC/cm2, remnant polarization of ∼0.4 μC/cm2 and coercive field of ∼0.3 MV/cm. This work opens a window for exploring novel polar topological effects in sub-10 nm thin film materials for non-volatile memory application.

Enhanced energy storage performance in Pb-free Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3-based relaxor ferroelectric ceramics through a stepwise optimization strategy

This study employed a stepwise optimization strategy, including doping Sr(Ga0.5Nb0.5)O3 (SGN) into 0.65Na0.5Bi0.5TiO3-0.35Sr0.7Bi0.2TiO3 (NBT-SBT) ceramics to modify the composition and a further processing improvement. By introducing Ga3+ and Nb5+ ions with high ionic polarization rates into the B-site, the average polarization of the unit cell was maintained while further inducing local disordered fields and promoting polar nanoregions. The high activity of the polar nanoregions was confirmed using piezoelectric microscopy. The effective energy storage density (Wrec) of 2.73 J/cm³ was obtained when the SGN doping was 6.5 %. Subsequently, the densification of ceramics was improved through viscous polymer processing, thereby enhancing the breakdown strength (BDS). A combined approach of finite element simulation and experimental studies was further utilized to investigate the impact of grain size on the BDS. The stepwise optimization strategy enabled the NBT-SBT-6.5SGNVPP ceramics to achieve the Wrec of 5.2 J/cm3 and efficiency (η) of 85 % under 350 kV/cm. Additionally, the ceramics developed by this strategy possess excellent temperature and frequency stability and pulse discharge performance, making them potential candidates for practical applications.

Understanding the depolarization phenomena in (1−x) Na0.5Bi0.5TiO3. (x) Ba0.85Ca0.15Ti0.90Zr0.10O3 solid solutions using in-situ temperature dependent Raman spectroscopy

A decrease in depolarization temperature (T d) from 456 K to 352 K was observed with an increase in BCZT substitution in the NBT for the (1−x) Na0.5Bi0.5TiO3. (x) Ba0.85Ca0.15Ti0.90Zr0.10O3 solid solutions. A transition towards a higher ergodic state was elucidated with an increase in BCZT content that helped to reduce the free energy barrier, hence lesser thermal energy was required to depolarize the modified systems. Furthermore, a decrease in remnant polarization and coercive field, coupled with an increase in energy storage (W stored) and efficiency (η%) with higher BCZT content. In-situ temperature-dependent Raman spectra provide additional insights, highlighting the faster changes in phonon shifts and lifetimes corresponding to the A–O, B–O, and BO6 vibrations around the depolarization temperature (T d). The observed phase transformation to a P4bm phase at temperatures significantly higher than T d is substantiated by Raman shift and phonon lifetime variations in the modes associated with the A–O and B–O vibrations. The transitions can be understood as: at T ∼ T d the polar nano regions (PNRs) start to appear due to weakening of bonds, T > T d all the long-range ferroelectric domains transform to PNRs converting the material to a fully ergodic state, and at much higher temperatures (T ≫ T d) the R3c PNRs vanish and P4bm PNRs appear.

High energy storage density achieved in BNT‐based ferroelectric translucent ceramics under low electric fields

AbstractThe development of ceramics with superior energy storage performance and transparency holds the potential to broaden their applications in various fields, including optoelectronics, energy storage devices, and transparent displays. However, designing a material that can achieve high energy density under low electric fields remains a challenge. In this work, (1−x)Bi0.5Na0.5TiO3−xBaZr0.3Ti0.7O3:0.6mol%Er3+ (abbreviated as (1−x)BNT−xBZT:0.6%Er3+) ferroelectric translucent ceramics were prepared by the conventional solid‐state reaction method. The energy storage properties of (1−x)BNT−xBZT:0.6%Er3+ are systematically investigated under low electric fields by modulating the coupling between coexisting phase structures of polar nano regions. Especially, 0.9BNT–0.1BZT:0.6%Er3+ ceramic exhibits an ultra‐high maximum polarization (Pmax = 66.3 µC/cm2), large recoverable energy storage density (Wrec = 2.95 J/cm3), total energy storage density (W = 5.75 J/cm3), and energy storage efficiency (η = 51.3%) under 190 kV/cm. The sample also exhibits excellent thermal stability (30‐150°C) and transmittance (∼28%). This work could facilitate the advancement of energy storage systems that are more efficient and cost‐effective, and also provide opportunities for the design and manufacture of novel devices.

High Energy Storage Performance in BiFeO3-Based Lead-Free High-Entropy Ferroelectrics.

Dielectric capacitors are widely used in advanced electrical and electronic systems due to the rapid charge/discharge rates and high power density. High comprehensive energy storage properties are the ultimate ambition in the field of application achievements. Here, the high-entropy strategy is proposed to design and fabricate single-phase homogeneous (Bi0.5Ba0.1Sr0.1Ca0.2Na0.1)(Fe0.5Ti0.3Zr0.1Nb0.1)O3 ceramic, the hierarchical heterostructure including rhombohedral-tetragonal multiphase nanoclusters and locally disordered oxygen octahedral tilt can lead to the increased dielectric relaxation, diffused phase transition, diverse local polarization configurations, grain refinement, ultrasmall polar nanoregions, large random field, delayed polarization saturation and improved breakdown field. Accordingly, a giant Wrec ≈13.3 J cm-3 and a high η ≈78% at 66.4kV mm-1 can be simultaneously achieved in the lead-free high-entropy BiFeO3-based ceramic, showing an obvious advantage in overall energy-storage properties over BiFeO3-based lead-free ceramics. Moreover, an ultrafast discharge rate (t0.9 = 18ns) can be achieved at room temperature, concomitant with favorable temperature stability in the range of 20-160 °C, due to the enhanced diffuse phase transition and fast polarization response. This work provides a feasible pathway to design and generate dielectric materials exhibiting high comprehensive energy-storage performance.

Achieving large strain and low hysteresis in BiFeO3-BaTiO3-based piezoelectric ceramics

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 BiFeO3-BaTiO3-(Ba0.6Sr0.4)TiO3 (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.

Novel NaNbO3-based relaxors featuring ultrahigh energy storage performance

Ferroelectric ceramics with ultrahigh power density and fast charging/discharging are attracting increasing attention. The practical application of most antiferroelectric ceramics in current electronics is significantly limited by their poor recoverable energy storage density. Here, a novel system ceramic of (1-x) Na0.84Ca0.16Nb0.84Ti0.16O3-xBiZn2/3Nb1/3O3 (NCNT-xBZN) solid solutions, possessing a giant Wrec∼7.05 J cm−3 and excellent conversion efficiency (η)∼83.7% under 53 kV mm−1, was synthesized to exhibit superior stability with changing temperature, frequency and fatigue behavior, together with the large current density (CD=571.8 A cm−2), ultrahigh power density (PD=85.7 MW cm−3) and ultrafast discharge rate (∼200 ns). These outstanding properties are attributed to the phase transformation from the AFE R to the FE Q phase, accompanied by the smashing of sub-microdomains into polar nanoregions, as the BZN content raises. The experimental results disclose that the synergistic effect of the highly dynamic response of polar nanoregions and the local lattice distortion arising from the disruption of long-range polar ordering by heterovalent ion filling generates a delayed saturation polarization with a strong relaxor behavior, thereby optimizing the energy storage density. The unique combination, together with a simple synthesis strategy, offers a refreshing strategy for the development of dielectric materials.

Excellent energy storage performance with high breakdown strength in Nb2O5-modified (Bi0.5Na0.5)TiO3-based ceramics

The development of lead-free dielectric capacitors with good energy storage performance and high reliability is of great practical significance for pulsed power systems. In this study, Nb2O5-modified 0.6(Bi0.5Na0.5)TiO3-0.4(Sr0.7Bi0.2)TiO3 (BNT-SBT-xNb, 0 ≤ x ≤ 0.07) ceramics were designed to enhance their energy storage performance and prepared using a hydrothermal method. The results show that Nb doping into the B site of BNT-SBT can induce lattice expansion and promote polar nanoregions, resulting in improved dielectric relaxation behavior. Moreover, the introduction of Nb can lead to the refinement of grain size, the increase in resistivity, the reduction of oxygen vacancies, and the broadening of band gap, thereby significantly enhancing the electrical breakdown strength (Eb). Accordingly, the BNT-SBT-0.05Nb system presents excellent energy storage performance with high Wrec ∼6.26 J/cm3 and η ∼87.9 % under an large Eb of 518 kV/cm in accompany with the wide temperature stability (Wrec and η vary within ±6.8 % and ±3.2 % at 40–100 °C). The significant improvement of Eb and energy storage performance demonstrates that the BNT-SBT-0.05Nb system is a potential candidate for applications in high-energy storage capacitors.

Excellent energy storage properties and multi-scale regulation mechanism of Sr(Zr0.5Ti0.5)O3-(Na0.5Bi0.5)0.94Ba0.06TiO3 ceramics

With the rapid advancement of energy storage technologies, dielectric capacitor materials with the outstanding recoverable energy density and power density have garnered significant attention from researchers in the past decades. In this study, (1-x) (Na0.5Bi0.5)0.94Ba0.06TiO3-xSr(Zr0.5Ti0.5)O3 ceramics were prepared via a solid-state reaction method, and the impact of composition on their structure, energy storage performance and stability were investigated. The results revealed that the introduction of Sr(Zr0.5Ti0.5)O3 induced the ferroelectric-relaxor transformation of (Na0.5Bi0.5)0.94Ba0.06TiO3 ceramics, leading to the destruction of the long-range ferroelectric order and the formation of polar nanoregions. In addition, the 0.7(Na0.5Bi0.5)0.94Ba0.06TiO3–0.3Sr(Zr0.5Ti0.5)O3 ceramic exhibited the optimal comprehensive energy storage performance: its recoverable energy storage Wrec attained 8.19 J/cm3 at 650 kV/cm, while the energy storage efficiency η was 85.6 %. Meanwhile, it displayed exceptionally high power density (315.7 MW/cm3) and charge-discharge rate (t0.9 = 50.4 ns). Moreover, this ceramic demonstrated the impressive energy storage performance, in particular, good temperature stability across a wide range of temperatures (20–140 °C), frequency stability (1–200 Hz), and fatigue resistance (1–106 cycles). Finite element analysis showed an enhancement in the breakdown field strength of the ceramics was attributed to the reduction in grain size. First-principles calculations revealed that the band gap increased after adding Sr and Zr elements, and the interactions between the states of O 2p and Ti 3d, Zr 3d, Bi 6p may serve as the microscopic origin of electron energy level polarization and enhanced dielectric performance. Thus, the ceramics have great potential for the application in high-power pulsed electronic systems.

Ultra-high strain in Bi0.5(Na0.41K0.09)TiO3 Pb-free piezoelectric ceramics modified by Sr(Hf0.5Sb0.4)O3

The lead-free piezoelectric ceramics used in piezoelectric actuators have attracted extensive attention owing to their substantial electric-field-induced strain. In this study, The (1-x)Bi0.5(Na0.41K0.09)TiO3-xSr(Hf0.5Sb0.4)O3 (BNKT-xSHS) piezoelectric ceramics were synthesized using the conventional solid-state reaction method. The impact of SHS substitution on the microstructure and electrical properties was systematically explored. Among them, the BNKT-0.015SHS sample, featuring ergodic relaxor states, demonstrates a high piezoelectric strain coefficient (d33*) of 785 p.m./V under a low electric field of 50 kV/cm(Strain = 0.392 %). It exhibits a repeatable strain value of 0.47 % under an 80 kV/cm electric field(d33* = 590 p.m./V). Moreover, the strain values remain around 0.4 % between room temperature and 100 °C, with variations within 90 %. The heightened repeatable strain response is considered to be linked to the electric field-induced reversible phase transition occurring within the ergodic relaxor state. The higher strain temperature stability is ascribed to the coexistence of quadrilateral polar nanoregions and rhombic polydomain nanoregions. This study provides an effective example for achieving significant strain responses, presenting a feasible candidate material for applications in piezoelectric actuators.

Robust Tunability and Newly Emerged Q Resonance of Ba0.8Sr0.2TiO3-Based Microwave Capacitors under Gamma Irradiations.

The complex resonance of dielectric quality factor Q, combined with a capacitance tunability n higher than 3:1 without any dispersion, was achieved in the voltage-tunable interdigital capacitors (IDCs) based on epitaxial Ba0.8Sr0.2TiO3 ferroelectric thin films across the microwave L (1-2 GHz), S (2-4 GHz), and C (4-8 GHz) bands at room temperature. The resonant Q and n features were driven by the microwave responses of the ferroelectric nanodomains engineered in the films. To promote their application in space radiation environments, the evolutions of Q and n both as functions of frequency f (1-8 GHz) and applied electric field E (0-240 kV/cm) were systematically investigated under a series of gamma-ray irradiations up to 100 kGy. The robust capacitance tunability was accompanied by the emergence of an additional Q resonance at 2.3 GHz in most post-irradiated devices, which is ascribed to extra polar nanoregions of expanded surface lattices associated with oxygen vacancies induced by irradiations.

Superior energy-storage density and ultrahigh efficiency in KNN-based ferroelectric ceramics via high-entropy design

The rapidly advancing energy storage performance of dielectric ceramics capacitors have garnered significant interest for applications in fast charge/discharge and high-power electronic techniques. Simultaneously improving the recoverable energy storage density Wrec and efficiency η becomes more prominent at the present time for their practical applications. Herein, a high-entropy concept is implemented on the (K0·5Na0.5)NbO3 (KNN)-based ferroelectric ceramics to design the high-performance dielectric capacitors. First, the strong lattice distortion can absorb some electric energy during the electrical loading process and result in the delayed polarization saturation. Additionally, the large composition fluctuations induce the weak correlation between polar nanoregions and enhance the η. Finally, the high-entropy design and viscous polymer processing method reduce the grain size and improve the Eb. In consequence, excellent Wrec of 11.14 J/cm3 with high η of 87.1% are achieved under an electric field of 750 kV/cm in the high-entropy component. These results demonstrate that the high-entropy concept is a potential avenue to design the KNN-based high-performance dielectric energy storage capacitors.

Enhanced ferroelectric and piezoelectric properties of Sb/Nb co‐doped BiScO3-PbTiO3-based ceramics via relaxation regulation near morphotropic phase boundary

Here, novel ferroelectric ceramics of Sb/Nb co-doped 0.36BiScO3-0.64PbTiO3 (BS-PT-Sb2O5-xNb2O5) of complex perovskite structure are reported with compositions near the morphotropic phase boundary (MPB) where the dominant monoclinic and tetragonal phases coexist. Excitingly, the incorporation of Sb/Nb dopants leads to a remarkable enhancement in both ferroelectric and piezoelectric properties. Notably, the sample with x = 1.0 demonstrates the optimal properties, boasting a giant piezoelectric coefficient (d33) of 498 pC/N (10.7 % higher than pure BS-PT ceramics), a high Curie temperature (Tc) of 392 °C, a high depolarization temperature of 362 °C and a large remanent polarization of 52.7 μC/cm2 (55.9 % higher than pure BS-PT ceramics). The enhanced ferroelectric and piezoelectric properties are ascribed to a relaxation behavior originating from the formation of polar nanoregions (PNRs) and reduced concentration of oxygen vacancy. The result provides an opportunity to elucidate the relationship between relaxation behavior and electrical properties, offering prospects for substantially improving the performance of piezoelectric ceramics.

Innovative Design of BNKT-xSLZT Ceramics: Maximizing the Polarization Difference for Enhanced Energy Storage.

Lead-free relaxor ferroelectric ceramics with outstanding energy-storage (ES) density (Wrec) and high ES efficiency (η) are crucial for advanced pulse-power capacitors. This study introduces a strategic approach to maximizing the polarization difference (ΔP) by inducing a transition from the ferroelectric phase to the ergodic relaxor (ER) phase. By employing this strategy, a series of ceramics, (1 - x)(Bi0.5Na0.4K0.1)TiO3-x(Sr0.85La0.1)(Zr0.5Ti0.5)O3 (BNKT-xSLZT), with varying SLZT content (x = 0.05, 0.10, 0.15, and 0.20), were designed. The addition of SLZT enhances cationic disorder, induces vacancies at A sites, and disrupts long-range ferroelectric order, facilitating the formation of polar nanoregions and enhancing relaxor ferroelectric behavior. Furthermore, a viscous polymer process (VPP) technology is employed to optimize the ceramics' structure, aiming to increase the breakdown strength (Eb) and enhance ΔP. Ultimately, enhanced ES performance is demonstrated in BNKT-0.15SLZTVPP, achieving a remarkable Wrec of 6.85 J/cm3 and η of 84% under 470 kV/cm. This composition demonstrates excellent stability with minimal variations in Wrec (3.0%) and η (4.4%) over the temperature range of 20-110 °C. Additionally, BNKT-0.15SLZTVPP exhibits exceptional pulse charge-discharge properties, featuring a high discharge density of 3.72 J/cm3, a large power density of 164.2 MW/cm3, and a short discharge time (t0.9) of 193 ns under 300 kV/cm. The study validates the practicality of BNKT-0.15SLZTVPP for pulse capacitors and underscores the potential to enhance ES performance through A-site donor doping and VPP technology. This work provides a comprehensive understanding of the interplay among composition, structure, and ES properties in lead-free relaxor dielectric ceramics, laying the groundwork for innovative advancements in the field.

Achieving High Energy Storage Performance under a Low Electric Field in KNbO3-Doped BNT-Based Ceramics.

Ceramic capacitors have great potential for application in power systems due to their fantastic energy storage performance (ESP) and wide operating temperature range. In this study, the (1 - x)Bi0.5Na0.47Li0.03Sn0.01Ti0.99O3-xKNbO3 (BNLST-xKN) energy storage ceramics were synthesized through the solid-phase reaction method. The addition of KN disrupts the long-range ferroelectric order of the BNLST ceramic, inducing the emergence of polar nanoregions (PNRs), which enhances the ESP of the ceramics. The BNLST-0.2KN ceramic demonstrates a high recovered energy density (Wrec ∼ 3.66 J/cm3) and efficiency (η ∼ 85.8%) under a low electric field of 210 kV/cm. Meantime, it exhibits a large current density (CD ∼ 831.74 A/cm2), high power density (PD ∼ 78.86 MW/cm3), and fast discharge rate (t0.9 ∼ 0.1 μs), along with good temperature stability and excellent fatigue stability. These properties make the BNLST-0.2KN ceramic a promising candidate for energy storage applications in low electric fields.

Improving energy storage properties of NN-NBT ceramics through compositional modification

Na0.5Bi0.5TiO3(NBT)-based ceramics are materials with good energy storage properties and non-ergodic relaxation ferroelectric properties, as well as high Curie temperature and good temperature stability. Herein, a new approach was devised to adjust the non-ergodic relaxation ferroelectric characteristics of Na0.5Bi0.5TiO3(NBT)-based ceramics by introducing NaNbO3 into Na0.5Bi0.5TiO3(NBT) (x NN-(1-x) NBT, where x= 0.17, 0.19, 0.21, 0.23, and 0.25). To overcome limitations of NBT, additional constituents with antiferroelectric properties were introduced to create binary solid solutions with NBT to yield NN-NBT ceramics with antiferroelectric properties for optimized energy storage applications. As-obtained NN-NBT ceramics revealed multiphase structures with rhombic (R3c) and tetrahedral (P4bm) phases. Coexisting strongly and weakly coupled polar nanoregions (PNRs) resulted in relatively high polarization (Pmax) and reduced polarization of reflection (Pr). The optimized 0.21NN-0.79NBT ceramic exhibited recoverable energy storage density of ≈2.84 J·cm−3 at 180 kv·cm−1 with energy storage efficiency of 78%. Structural characterization indicated the existence of intermediate phases modulation phases with coexisting antiferroelectric phase and relaxation ferroelectric phase. Overall, proposed NBT-based non-ergodic relaxation ferroelectric ceramics look promising for effectively improving energy storage performance, providing new prospects for the development of advanced pulse capacitors.

Ultrahigh energy storage performance in AN-based superparaelectric ceramics

Ceramics capacitors, especially featuring antiferroelectric (AFE) structure, are widely used in pulsed power electronic systems due to distinctive high-power density and external field stability. Lead-free AFE material AgNbO3 has seized substantial research attention owing to its unique temperature driven multi-level phase transitions, and many works have greatly improved the energy storage properties by engineering these temperature-dependent phase boundaries. In this work, an ever-unadopted strategy was proposed to modulate the relaxor structure in AgNbO3 by designing room-temperature (RT) superparaelectric phase via Bi incorporation into AN lattice matrix. Structural analysis shows M phase (space group Pbcm) evolves into O phase (space group Cmcm) with 12 mol.% Bi-substitution, breaking the long-range AFE order into polar nanoregions. Hence, an ultra-high recoverable energy density (7.6 J/cm3) and a high efficiency (79 %) are simultaneously achieved in the Ag0.64Bi0.12NbO3 ceramics under 52.2 kV/mm. Moreover, the excellent energy storage properties are accompanied with good temperature and frequency stability, with the variation of Wrec less than ± 15% (over 25–120 °C) and ± 10% (over 1–200 Hz) under 25 kV/mm, respectively. The novel approach reported herein provides a new guidance for designing AgNbO3-based and other AFE materials for high-performance energy storage applications.

Phase transition and large strain response with ultra-low hysteresis of BaTiO3 doped with a high-entropy perovskite oxide

(1 − x)BaTiO3–xBi(Sc0.2Y0.2Al0.2Fe0.2Ga0.2)O3 (BT–BSYAFG, x = 0.02, 0.04, 0.06, 0.08, and 0.10) ceramics were successfully prepared via the solid-state reaction method. X-ray diffraction and Raman spectroscopy results reveal that a structural transition from the tetragonal (P4mm) to the pseudocubic (Pm3¯m) phase occurs with increasing x. At x = 0.04 and 0.06, the tetragonal and pseudocubic phases coexist. The relaxor behavior of the as-prepared samples is enhanced via BSYAFG doping due to the lattice distortion effect of high-entropy perovskite oxides. Additionally, the transition from the classic ferroelectric to the relaxor ferroelectric state implies that the long-range-ordered macro-domains are completely transformed into disordered polar nano-regions, which improves the strain properties. A large strain response (0.28 %) with an ultra-low hysteresis (4 %) is achieved at x = 0.06 under an electric field of 70 kV/cm. These results indicate that BT–BSYAFG ceramics are promising materials for application to the field of precision actuators.