Relaxor Research Articles

Bridging the gap between the short-range to long-range structural descriptions of the lead magnesium niobate relaxor

The structure-property relationships on different length scales and their connections to the macroscopic piezoelectric and dielectric properties are one of the most fascinating topics of relaxor ferroelectrics and need to be further explored. Here, we provide structural insights into the gap between the short-range structure and the long-range structure of the classical relaxor ferroelectric lead magnesium niobate (PMN) using a combination of theoretical simulations and pair distribution function (PDF) analysis. Our study shows that PMN exhibits a disordered low-symmetry structure at the smallest length scale (1–10 Å) and a cubic crystallographic average structure at large length scale. A rhombohedral phase is observed at the intermediate length scale (∼ 20–70 Å), resulting from chemical ordered regions with the ordered local electric field and associated quasi-correlated Pb displacements. Our work advances the understanding of the structures of relaxor ferroelectrics at different length scales and the relationships among them.

Relaxor antiferroelectric-relaxor ferroelectric crossover in NaNbO3-based lead-free ceramics for high-efficiency large-capacitive energy storage

Relaxor ferroic dielectrics have garnered increasing attention in the past decade as promising materials for energy storage. Among them, relaxor antiferroelectrics (AFEs) and relaxor ferroelectrics (FEs) have shown great promise in term of high energy storage density and efficiency, respectively. In this study, a unique phase transition from relaxor AFE to relaxor FE was achieved for the first time by introducing strong-ferroelectricity BaTiO3 into NaNbO3-BiFeO3 system, leading to an evolution from AFE R hierarchical nanodomains to FE polar nanoregions. A novel medium state, consisting of relaxor AFE and relaxor FE, was identified in the crossover of 0.88NaNbO3–0.07BiFeO3–0.05BaTiO3 ceramic, exhibiting a distinctive core-shell grain structure due to the composition segregation. By harnessing the advantages of high energy storage density from relaxor AFE and large efficiency from relaxor FE, the ceramic showcased excellent overall energy storage properties. It achieved a substantial recoverable energy storage density Wrec ∼ 13.1 J/cm3 and an ultrahigh efficiency η ∼ 88.9%. These remarkable values shattered the trade-off relationship typically observed in most dielectric capacitors between Wrec and η. The findings of this study provide valuable insights for the design of ceramic capacitors with enhanced performance, specifically targeting the development of next generation pulse power devices.

Achieving superb electric energy storage in relaxor ferroelectric BiFeO3-BaTiO3-NaNbO3 ceramics via O2 atmosphere

Lead-free perovskite dielectric materials for storing electrical energy have been widely investigated due to their high polarization and reversible phase. However, their low electric resistivity limits the energy density and stability. In this study, the (1-x)(0.7BiFeO3-0.3BaTiO3)-xNaNbO3 ceramics (x = 0 – 0.2) were prepared using two sintering atmospheres (air and oxygen). A superb recoverable energy-stored density (Wrec) of 8.2 J/cm3 and efficiency (η) of 70% was achieved at x = 0.15 sintered in O2 atmosphere. The superior Wrec is due to the structural coexistence of ferroelectric rhombohedral (R3c), nonpolar cubic (Pm-3m), and antiferroelectric orthorhombic (Pbam) symmetries, tailored via antiferroelectric NaNbO3 addition. The improved breakdown strengths (up to 325 kV/cm) are due to the increased interatomic bonding linked to the BO6 octahedron and lattice network. Altogether, NaNbO3-substitution and O2 sintering synergistically resulted in excellent energy storage and pave a scheme of antiferroelectric-tailoring BiFeO3-BaTiO3–NaNbO3 relaxor ferroelectrics for dielectric capacitor.

Phase transition monitoring and temperature sensing via FIR technology in Bi/Sm‐codoped KNN transparent ceramics

AbstractThe phase transition temperature (e.g., that of orthorhombic‐tetragonal TO‐T) of relaxor ferroelectrics are commonly obtained through electrical method (i.e., temperature dependence of dielectric constant), and the samples need to be coated with metal electrode and tested by a sophisticated impedance analyzer. This contact measuring method is inefficient, inconvenient and easy to damage the sample surface, inapplicable to transparent ferroelectrics. Here, we successfully fabricated Bi/Sm co‐doped K0.5Na0.5NbO3 transparent ceramics with photoluminescent behavior and relaxor‐like ferroelectricity, which simultaneously realized TO‐T monitoring and temperature sensing via fluorescence intensity ratio (FIR) technology. This simple, rapid, noncontact and nondestructive optical way displays small TO‐T deviation (merely 0.78%) compared to the electrical method. And the temperature‐dependent optical characteristics and coercive electric field all present abrupt changes, whose abnormal temperature regions are in accordance with that around TO‐T. In addition, the maximum absolute sensitivity and relative sensitivity of the ceramics reach 0.0072 K−1 (at 533 K) and 0.0111 K−1 (at 453 K), respectively, exhibiting superior optical temperature sensing performance. The tactical use of FIR technology is of great significance for widening the applications of luminescent‐ferroelectric transparent ceramics.

On the random temperature model for relaxors

The dependence of the Burns temperature on the parameters of the regions of structural heterogeneity was determined and the freezing temperature of a separate polar nanoregion was estimated within the framework of the phenomenological model of random temperature proposed to describe the properties of ferroelectric relaxors. It is shown that taking into account the temperature dependence of the free energy of the polar region is important for determining the dependence of the relaxation frequency on temperature.

Enhanced piezoelectric properties and electrical resistivity in CaHfO3 modified BiFeO3[sbnd]BaTiO3 lead-free piezoceramics

A number of CaHfO3 modified BiFeO3-0.33BaTiO3 (BF-0.33BT-xCH) lead-free piezoceramics were fabricated through the solid-state sintering method and comprehensively investigated in this work. Under the optimal sintering temperature, all compositions display a typical perovskite structure in a pseudo-cubic phase with slightly larger lattice parameters as the CH content increases. The electrical resistivity is highly enhanced due to the addition of CH. Microstructures, including the grain morphology, core-shell structure, and chemistry inhomogeneities, are demonstrated upon different BF-0.33BT-xCH compositions. In particular, the core-shell structures with non-uniform element distributions in the compositions can be eliminated by adding sufficient CH content (x > 0.05). The highest saturation polarization (40.1 μC/cm2), remnant polarization (26.8 μC/cm2), and converse piezoelectric coefficient (290 pm/V) are achieved in the BF-0.33BT-0.01CH piezoceramic, which are significantly enhanced in comparison with the undoped BF-0.33BT piezoceramic. With further increasing the CH content, the piezoelectric properties of BF-0.33BT-xCH ceramics decline rapidly, and they start to exhibit characteristics of relaxor ferroelectrics.

Enhanced energy‐storage properties in Zr4+‐modified (Bi0.4Ba0.2K0.2Na0.2)TiO3 high‐entropy ceramics

AbstractRecently, high‐entropy perovskite oxides (HEPOs) have received increasing interest for energy storage applications owing to their unique structure, huge composition space, and promising properties. However, designing HEPOs with improved energy storage performance remains a challenge. In this study, various HEPOs were designed by partially replacing Zr4+ for Ti4+ in (Bi0.4Ba0.2K0.2Na0.2)TiO3 medium‐entropy ferroelectric ceramics. The resulting ceramics exhibited a pseudo‐cubic structure. With increasing Zr4+ content, the ceramics gradually transformed into relaxor ferroelectrics. The energy storage performance of the ceramics depended on the Zr4+ content. The sample with 20 mol% Zr4+ showed the best energy storage performance with a maximum reversible energy density of 2.47 J/cm3 and an energy storage efficiency of 82.3% at a low applied electric field (224 kV/cm). This study obtained a promising material for the new generation dielectric energy storage capacitors and provided a novel method for enhancing energy storage performance.

Effect of the DC-bias electric field on the phase transition characteristics in PMN ceramics

Relaxor ferroelectrics play an important role for technological applications, mainly for using in the fabrication of actuators, transducers and sensors. Therefore, there has been an increasing interest of the scientific community in the investigation of the physical properties of such system in order to better elucidate the observed intriguing and unsolved phenomena. In this work, relaxor Pb(Mg1/3Nb2/3)O3 (PMN) ceramic system was prepared and the dielectric properties have been studied in details as a function of frequency, temperature and magnitude of the DC-bias electric field. Results reveal that the temperature dependence of the dielectric permittivity can be successfully described in the whole analyzed temperature range (100–400 K) by using a macroscopic statistical model, which describe the dielectric response in relaxor systems with diffuse phase transition (DPT). By using this phenomenological model, the temperature and DC-bias electric field dependences of the dielectric permittivity have been also revisited, from the analysis of the DPT behavior, promoting a careful discussion on the nature of the phase transition in relaxors materials. The calculated sizes of the polar nanoregions (PNRs) suggest the development of a structural disorder in the studied system, which promote the high diffuse ferroelectric transition as the amplitude of the DC-bias electric field increases.

Attaining excellent piezoelectric properties and thermal stability in PIN-PHT ceramics by integrating tetragonal phase and relaxor ferroelectrics

Herein, Nd2O3-doped 0.11PIN-0.89PHT (PIN-PHT) single-phase tetragonal piezoelectric ceramics are prepared by traditional solid-phase method. In addition, impacts of Nd-doping on crystal structure and electrical performance for 0.11PIN-0.89PHT ceramics are systematically investigated. Based on Landau theory, we propose a novel strategy for obtaining high-performance ceramics by combining tetragonal phase and relaxor ferroelectrics. Results reveal that the introduction of polar nano-regions in tetragonal phase ceramics by doping with rare-earth ions to convert normal ferroelectrics into relaxed ferroelectrics is responsible for excellent properties of 0.11PIN-0.89PHT-xNd ceramics. The optimized comprehensive performance is obtained at x = 0.9 mol%, where d33 = 670 pC/N, Smax = 0.29% (45 kV/cm), strain hysteresis = 8.68% (45 kV/cm), d33* = 736 p.m./V (30 kV/cm), TC = 312.6 °C, εr = 3234, kp = 0.62, tanδ = 0.014, and excellent high-temperature stability in temperature range of 20–240 °C. After 106 cycles, electrical properties and strain remain unchanged, showing excellent anti-fatigue behavior. This work provides a novel approach for the development of ceramics with outstanding piezoelectric response, high strain, low strain hysteresis, excellent anti-fatigue resistance and thermal stability, and is expected to realize practical applications of piezoelectric ceramics.

Electrocaloric effect of (Ba1-xSrx)(HfxTi1-x)O3 lead-free ferroelectric ceramics with phase structure regulation

Electrocaloric (EC) refrigeration is a new type of solid-state refrigeration technology based on the electrocaloric effect (ECE), which has the advantages of environmental protection, high efficiency, easy integration and miniaturization. In this paper, Sr2+ and Hf4+ are doped into the A and B sites of BaTiO3 (BT), respectively. By adjusting the proportional composition, the multicritical point is constructed to improve the adiabatic temperature change (ΔT), and the relaxor ferroelectrics are formed to broaden the working temperature span (Tspan). The effect of doping content on the crystal structure, surface morphology, dielectric, ferroelectric and electrocaloric properties of ceramics is studied systematically. The phase diagram of (Ba1-xSrx)(HfxTi1-x)O3 (BSHT) ceramics is established, and (Ba0.9Sr0.1)(Hf0.1Ti0.9)O3 (BSHT10) is at the multicritical point. It has the most excellent comprehensive electrocaloric performance, with ΔTmax obtained 1.2 K and Tspan (ΔT ≥ 0.9 ΔTmax) reached 45 °C under 50 kV/cm, indicating its potential as a lead-free bulk ceramic material for EC refrigeration applications.

Enhanced Energy Storage Performance and Efficiency in Bi0.5(Na0.8K0.2)0.5TiO3-Bi0.2Sr0.7TiO3 Relaxor Ferroelectric Ceramics via Domain Engineering.

Dielectric materials are highly desired for pulsed power capacitors due to their ultra-fast charge-discharge rate and excellent fatigue behavior. Nevertheless, the low energy storage density caused by the low breakdown strength has been the main challenge for practical applications. Herein, we report the electric energy storage properties of (1 - x) Bi0.5(Na0.8K0.2)0.5TiO3-xBi0.2Sr0.7TiO3 (BNKT-BST; x = 0.15-0.50) relaxor ferroelectric ceramics that are enhanced via a domain engineering method. A rhombohedral-tetragonal phase, the formation of highly dynamic PNRs, and a dense microstructure are confirmed from XRD, Raman vibrational spectra, and microscopic investigations. The relative dielectric permittivity (2664 at 1 kHz) and loss factor (0.058) were gradually improved with BST (x = 0.45). The incorporation of BST into BNKT can disturb the long-range ferroelectric order, lowering the dielectric maximum temperature Tm and inducing the formation of highly dynamic polar nano-regions. In addition, the Tm shifts toward a high temperature with frequency and a diffuse phase transition, indicating relaxor ferroelectric characteristics of BNKT-BST ceramics, which is confirmed by the modified Curie-Weiss law. The rhombohedral-tetragonal phase, fine grain size, and lowered Tm with relaxor properties synergistically contribute to a high Pmax and low Pr, improving the breakdown strength with BST and resulting in a high recoverable energy density Wrec of 0.81 J/cm3 and a high energy efficiency η of 86.95% at 90 kV/cm for x = 0.45.

Optimization of polarization behavior enabled by multiscale heterostructure design for excellent energy storage performance in Na0.5Bi0.5TiO3-based relaxor ferroelectric thin film

Dielectric capacitors are promising candidates in the field of pulse power systems due to their ultrafast charge/discharge speed and high power density. A major challenge, however, is to improve the recoverable energy storage density (Wrec) and energy storage efficiency (η). In this work, Na0.5Bi0.5(Ti,Fe)O3 (NBFT)-based system is selected and the equivalent circuit of the corresponding capacitors is studied according to the Maxwell's displacement current hypothesis, providing a way of optimizing the polarization behavior by multiscale heterostructure design via adjusting the specific arrangement of layers and interface within the NBFT-based capacitors. By introducing heterogeneous components of (Ba,Sr)TiO3 (BST) and Na0.5Bi0.5(Ti,Zr)O3 (NBZT), abundant heterogeneous interfaces are obtained for NBFT/BSxT and NBFT/NBZT heterostructure thin films. Both the thin films possess superior breakdown strength (EBD) and polarization response (Pm–Pr) than that of NBFT, which is highly associated with the interfacial resistance, improvement of local component heterogeneity, changes in domain wall motion and Von Mises stress/strain distribution. Notably, the energy storage performance is modulated for NBFT/NBZT with enhanced relaxor ferroelectricity as the heterogeneous interface is increased with Wrec and η of 66.57 J/cm3 and 64.33%, respectively. These findings prove effective ways of optimizing NBT-based relaxor ferroelectric thin film for energy storage devices.

Enhancement of energy storage performance in lead‐free relaxor ferroelectric ceramics via band structure engineering

AbstractDielectric capacitors with excellent energy storage performance (ESP) are in great demand in the power electronics industry due to their high power density. For the dielectric materials, the dielectric breakdown strength (BDS) is the key factor to improve ESP, which is the focus and bottleneck of current research, especially in the relaxor ferroelectric (RFE) materials with already low residual polarization (Pr). Here, we stimulate the ESP of the BaTiO3 (BT)‐based RFE ceramics by band structure engineering. The Ta element is selected to enhance the band gap of doped ceramics, occupying Ti‐site in supercell of BT and optimizing the bonds length of Ti‐O bond to increase the energy band of Ti 3d states. In this way, the band gap of the doped ceramics is efficiently enhanced from 1.8 eV to 2.22 eV resulting in the large BDS. Prospectively, combined with the advantage of fine grain size, the highest recoverable energy storage density (Wrec) of 2.85 J/cm3 is obtained at 350 kV/cm and the ultra‐high energy efficiency (η) of 95.26% is found at 200 kV/cm. Our work reveals the relationship between elements doping in B‐site and band structure, being expected to benefit for designing energy storage materials.

Simultaneously realizing ultrahigh energy storage density and efficiency in BaTiO3-based dielectric ceramics by creating highly dynamic polar nanoregions and intrinsic conduction

Nowadays, it is urgent to explore advanced and eco-friendly energy storage capacitors based on lead-free relaxor ferroelectric (RFE) ceramics in order to meet the ever-increasing requirements in pulsed power systems. BaTiO3 (BT)-based RFE ceramics are considered as ones of the best high-temperature energy storage materials due to their good thermal stability. However, relatively low recoverable energy storage density (Wrec<5 J/cm3) has been a key bottleneck restricting the practical applications of them. Here, a novel strategy is proposed to create highly dynamic PNRs and the intrinsic conduction by introducing Bi(M1-0.015xTa0.015x)O3+0.015x (BMO-Ta, M=Mg2/3Ta1/3) to BT matrix. As a consequence, the designed (1-x)BT-x(BMO-Ta) ceramics exhibit dramatically enhanced energy storage properties including ultrahigh Wrec and efficiency (η), because of the coexistence of very slim polarization hysteresis (P-E) loops, large polarization difference (ΔP) and giant dielectric breakdown electric strength (Eb). Wrec and η of the x=0.25 ceramic reach up to 9.03 J/cm3 and 95.2% under 720 kV/cm, respectively. Furthermore, it shows excellent temperature/frequency/cycling stability over a wide range of 20−200 °C, 1−500 Hz and 1−3.3 × 105 cycles, respectively (the variations of Wrec and η are < 3% and < 4%, respectively). The findings in this paper not only indicate excellent comprehensive properties achieved in the novel (1-x)BT-x(BMO-Ta) system, but also provide an effective approach to explore advanced energy storage capacitors in other lead-free ceramic systems.

Phase-Transition Induced Optimization of Energy Storage and Temperature Stability of NaNbO3 Doped BNBST Ceramics

The 0.5Bi0.5Na0.5TiO3−0.5Ba0.3Sr0.7TiO3 (BNBST) ceramic is a relatively good relaxation component with tripartite phase and tetragonal phase coexisting at room temperature. Tripartite R3c is a polar phase, which can transform to long range ordered ferroelectric structures under the action of an applied electric field, exhibiting large remnant polarization (P r), which limits its application in energy storage. In this work, we designed NaNbO3 (NN) modified Bi0.5Na0.5TiO3-Ba0.3Sr0.7TiO3 ceramics to prepare (1−x) (0.5Bi0.5Na0.5TiO3−0.5Ba0.3Sr0.7TiO3)−xNaNbO3 (abbreviated as (1−x)BNBST-Xnn, x = 0, 0.05, 0.10, 0.15, 0.20, 0.25) relaxor ferroelectrics. By increasing the NN amount, the phase composition is regulated to induce the transformation of the polar phase R3c to the weakly polar phase P4bm, leading to a smaller P r. The ferroelectric test results show that the ceramic sample with x = 0.1 achieves a high effective energy storage density (W rec = 2.58 J cm−3) and energy storage efficiency (ƞ = 91%) at 140 kV cm−1.

Decoding the Atomic-Scale Structural Origin of Large Strain Performance in BNT-6BT Based Relaxor Ferroelectrics.

The relationship between matter properties and their atomic-scale structures is a challenging investigation. For relaxor ferroelectrics, correlating the relaxor mechanisms on the atomic scale to properties is still ambiguous. Here, the correlation between the atomic-scale structure and strain performance of 0.94 Bi0.5Na0.5TiO3-0.06BaTiO3 (94BNT-6BT) and 0.93 Bi0.5Na0.5TiO3-0.06BaTiO3-0.01BaZrO3 (93BNT-6BT-1BZ) is reported. The δTi-Bi/Na displacement vector map based on the annular dark field (ADF) scanning transmission electron microscopy (STEM) image demonstrates the coexistence of tetragonal (T) and rhombohedral (R) phases of the resulting ceramics, and BZ doping increases the proportion of the T phase. Furthermore, the enhanced annular bright field (eABF) STEM image demonstrates that BZ doped ceramics exhibit obvious oxygen octahedral tilt. The oxygen octahedral tilt increased gradually from the domain wall to the inner place of the nanodomain, indicating a regional consistency, which results in enhancement of the relaxor performance and stain property. This study opens exciting opportunities to the design of relaxor ferroelectrics with large strain for high-displacement actuator applications.

Hierarchically polar structures induced superb energy storage properties for relaxor Bi0.5Na0.5TiO3-based ceramics

Electrostatic capacitors are fundamental components in electronics and electric power systems because of their inherent superiorities of charging/discharging speed and power density. However, energy storage properties (ESPs) of the top promising relaxor ferroelectric (RFE) are intimately entwined symmetry of local lattice and dynamics of nano-scaled polar structure. Herein, hierarchically polar structure and oxygen octahedral tilting can be induced in the 0.7Bi0.5Na0.5TiO3-0.3Na0.91Bi0.09Nb0.94Mg0.06O3 (BNT-NBNM) matrix with the addition of CaZrO3 (CZ) to achieve outstanding comprehensive ESPs. The chemically induced coexisting triple phases of tetragonal P4bm, orthorhombic P21ma and Pnma2 bring forth hierarchically polar structure, featuring nanodomains and slush-like polar clusters embedded in stripe submicro-domains, as indicated by morphological observations, splitting of diffraction spots and polar state distributions. Accordingly, an ultrahigh recoverable energy storage density Wrec = 7.5 J cm−3 concurrent with a high-efficiency η = 94.5 % at a breakdown electric field of 510 kV cm−1 can be attained in BNT-NBNM-0.05CZ RFE ceramic. In addition, the optimal composition also displays excellent stability (Wrec = 5.1 ± 0.1 J cm−3, η = 92.7% ± 1%, 20–170 °C and Wrec = 5.2 ± 0.2 J cm−3, η = 92.1% ± 1.3%, 5–500 Hz) at 410 kV cm−1. The present work provides a new perspective for designing lead-free RFE ceramics with ultra-high ESPs that benefit from hierarchically polar structures.

Stretchable polymer composites with ultrahigh piezoelectric performance.

Flexible piezoelectric materials capable of withstanding large deformation play key roles in flexible electronics. Ferroelectric ceramics with a high piezoelectric coefficient are inherently brittle, whereas polar polymers exhibit a low piezoelectric coefficient. Here we report a highly stretchable/compressible piezoelectric composite composed of ferroelectric ceramic skeleton, elastomer matrix and relaxor ferroelectric-based hybrid at the ceramic/matrix interface as dielectric transition layers, exhibiting a giant piezoelectric coefficient of 250 picometers per volt, high electromechanical coupling factor keff of 65%, ultralow acoustic impedance of 3MRyl and high cyclic stability under 50% compression strain. The superior flexibility and piezoelectric properties are attributed to the electric polarization and mechanical load transfer paths formed by the ceramic skeleton, and dielectric mismatch mitigation between ceramic fillers and elastomer matrix by the dielectric transition layer. The synergistic fusion of ultrahigh piezoelectric properties and superior flexibility in these polymer composites is expected to drive emerging applications in flexible smart electronics.

Comprehending the underlying mechanism behind directly/indirectly obtained large electrocaloric response in Bi0.5Na0.5TiO3-based relaxor ferroelectrics

Lead-free ferroelectric electrocaloric (EC) materials are promising candidates for the next generation of cooling materials. Bi0.5Na0.5TiO3 (BNT)-based relaxor ferroelectrics, one of the most representative EC materials, exhibit a superior electrocaloric effect (ECE) near the depolarization temperature (Td). However, there are more and more concerns over the reliability of the widely used indirect measurement method. Here, to comprehend the difference between indirectly and directly obtained ECE results in BNT-based system, the applicability of indirect measurement (based on Maxwell equation) was critically analyzed with respect to the reliable direct measurement (based on heat flow). As evidenced in prototypical BNT-based compositions with different Td values, the dynamic behaviors of local polar structures including ferroelectric domains and polar nano-sized regions (PNRs), can largely affect the measured polarization and thus affect the reliability of indirect measurement. After systematically comparing and analyzing the composition-, temperature-, electric field (E-field)-dependent ECE results obtained from indirect and direct ways, the applicable working regions for the indirect method were determined. This work reveals the underlying mechanism behind direct and indirect ECE measurements, providing the “indirect + direct” experimental strategy for effectively evaluating the ECE performance in BNT-based relaxor ferroelectrics.

Influence of NaNbO3 addition to Bi0.5(Na0.8K0.2)0.5TiO3 lead-free ceramics on the energy storage properties

(1-x)Bi0·5(Na0·8K0.2)0.5TiO3/xNaNbO3 (x = 0–0.1) ceramics are prepared through solid-state reaction. The incorporation of NaNbO3 leads to slight crystal distortion with nanoscale particle size, improving the relaxor phenomenon by destruction of the original ferroelectric long-range order, which finally contributes to the enhanced energy storage density and efficiency. Particularly, the outstanding energy storage properties are observed at x = 0.075 with well thermal, frequency and cycle stability. Moreover, the highest energy storage density and efficiency are obtained at ∼160 °C with x = 0.075. Further, the well charge-discharge performance is also achieved. These results indicate that designing Bi0·5(Na0·8K0.2)0.5TiO3-based relaxor ferroelectrics through NaNbO3 is an effective method to realize excellent energy storage performance in dielectric capacitors.