Non-polar nanocluster confinement engineering realizes high capacitive energy storage in Pb-free high-entropy relaxors

Domain: chemistry
Published: 2026-01-12
Editorial outcome: major_revision

Abstract
Dielectric ceramic capacitors with ultrahigh power density have become indispensable in modern power electronics, yet the persistent challenge of achieving superior energy density with high energy efficiency remains a critical bottleneck for practical applications. Herein, we propose an effective non-polar nanocluster confinement strategy through phase-field simulation-guided design of high-entropy (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)(Ti1-xSnx)O3 lead-free relaxor ferroelectrics. The incorporation of Sn4+ ions with low ionic polarizability leads to the formation of localized non-ferroelectric perovskite units, which constitute robust non-polar nanoclusters, being further stabilized and rendered immobile against electric fields by the substantial local random fields inherent to the high-entropy configuration. Consequently, these engineered non-polar nanoclusters serve as effective pinning centers to impede the merging and growth of polar nanodomains under electric fields, thereby reconciling the inherent conflict between polarization enhancement and hysteresis reduction. The optimized composition (x = 0.06) exhibits a high recoverable energy density of ~18.5 J·cm-3 together with an ultrahigh energy efficiency of ~92.4% in multilayer ceramic capacitors, representing a competitive combination among lead-free counterparts. This approach not only establishes a viable paradigm for next-generation energy storage dielectrics but also provides fundamental insights for designing functional materials with tailored electrical properties.

Introduction
High-performance dielectric energy-storage capacitors are critical components for next-generation high/pulsed power electronic systems, driven by escalating demands for advanced energy conversion and management technologies1–3. Distinguished by their unique electrostatic energy-storage mechanism, dielectric capacitors offer unparalleled advantages, including the highest power density (~107–108 W/kg) among energy-storage devices, ultra-fast charge/discharge rates on nanosecond timescales, and exceptional operational longevity exceeding 105 cycles4–8. These characteristics make them indispensable in mission-critical applications, such as medical defibrillators, electromagnetic armor systems, and hybrid electric vehicle powertrains.

Multilayer ceramic capacitors (MLCCs) have attracted considerable attention as promising candidates for next-generation energy storage8–16. In contrast to bulk ceramic capacitors, their layered architecture enhances dielectric breakdown strength (EB) through the thinning of individual ceramic layers and improves volumetric efficiency via compact stacking of alternating dielectric and electrode layers8–16. While thin-film capacitors can attain higher EB and thus larger energy storage density (Wrec) owing to their sub-micron thickness, their limited active volume substantially restricts the total storable energy, making them less suitable for macro‑scale applications compared to MLCCs3,14. Nevertheless, the energy-storage performance of MLCCs remains fundamentally limited by the intrinsic properties of their ceramic dielectrics, particularly the challenge of achieving both high Wrec and high energy efficiency (η) simultaneously.

The energy storage performance of dielectric materials is governed by their polarization response under electric fields, where achieving high maximum polarization (Pmax) with minimal hysteresis is essential for obtaining high Wrec and η4–8. Recent advances have explored various strategies to optimize polarization response, including nanodomain engineering8,11,16, superparaelectric design17,18, defect engineering19, multiphase construction3,13, lattice strain modulation14, relaxor antiferroelectric (AFE) strategy20,21 and composite ceramic design9,22, etc. Especially, high-entropy ferroelectric (FE) materials featuring multi-elemental occupation of equivalent lattice sites have recently demonstrated exceptional potential for energy storage because that the atomic-scale compositional heterogeneity induces substantial local structural disorder and generates larger andomelectric/stress fields3,12,23–26. These features are highly desirable for enhancing energy storage performance. The above advancements have also catalyzed extensive exploration of various lead-free FE and AFE ceramic systems, including BaTiO3 (BT)3,11,13,18,23,26, Bi0.5Na0.5TiO3 (BNT)9,10,14, K0.5Na0.5NbO3 (KNN)27,28, BiFeO3 (BF)16,25, NaNbO3 (NN)20,24, and AgNbO3 (AN)-based materials19,21. Despite these advances, the intrinsic trade-off between Wrec and η remains a critical bottleneck in both relaxor FEs and AFEs. Excessive polarization hysteresis and consequent η degradation under high electric fields continue to impede progress, primarily due to the electric-field-induced growth of nanodomains. Therefore, the synergistic achievement of superior Wrec (>15 J cm−3) and ultrahigh η (>90%) presents a formidable challenge in lead-free ceramics and MLCCs (Table S1, Supplementary Information)4–7,9–16,18–30.

Herein, we propose a novel strategy of nonpolar nanocluster confinement to inhibit the electric-field-induced growth of polar nanodomains in high-entropy relaxor FEs, thereby enabling concurrent enhancement of polarization and reduction of hysteresis, as schematically illustrated in Fig. 1. We selected a representative high-entropy relaxor composition, (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3, which exhibits significant A-site cationic disorder, as the matrix31–33. Sn4+, which possesses extremely low ionic polarizability compared to other commonly used B-site cations, was introduced at the B-site34,35. Given that SrSnO3, CaSnO3, and BaSnO3 are all non-FE perovskites36,37, the Sn-rich regions that form at the atomic scale are expected to behave as non-polar clusters, exhibiting limited responsiveness to electric fields and thus not contributing to polarization growth. Furthermore, the incorporation of Sn4+ coupled with different A-site cations introduces varied lattice distortions, which enhances local random fields. This effect not only reduces the size of the polar domains but also further confines the Sn-rich nonpolar nanoclusters. Under increasing electric fields, these confined non-polar regions effectively impede the merging and growth of adjacent polar nanodomains, as depicted in Fig. 1a. This design concept is corroborated by our phase-field simulations of the domain structure evolution in (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)(Ti1-xSnx)O3 (BNBSCT1-xSx) ceramics (Fig. 1b). The simulated P-E loops demonstrate an improved polarization-field response along with significantly reduced hysteresis (Fig. 1c). Experimentally, we realized a desirable polarization-field response characterized by an extremely low hysteresis and a high Pmax in BNBSCT1-xSx bulk ceramics with x = 0.06. This yields a superior Wrec of ~18.5 J cm−3 and an ultrahigh η of ~92.4% under ~108 kV mm−1, representing a notable advancement in the comprehensive energy-storage properties of lead-free MLCCs.

Results
Guided by the phase-field simulation predictions, we designed and synthesized a series of BNBSCT1-xSx high-entropy ceramics. X-ray diffraction patterns (Fig. S1) confirms the formation of single-phase perovskite structures across all compositions. Microstructural analysis reveals dense ceramic packing with well-defined grain boundaries (Fig. S2), where the refined grain morphology significantly enhances EB7,29. To experimentally validate the phase-field predictions regarding domain confinement, we investigated the electric-field-induced domain evolution using in situ piezoresponse force microscopy (PFM), as shown in Fig. 2a. At low voltage (10 V), featureless amplitude images indicative of polar nanoregions are observed across all compositions, confirming their relaxor FE nature38,39. This behavior is further evidenced by temperature-dependent dielectric spectroscopy (Fig. S3), revealing typical relaxor characteristics40,41. These characteristics likely originate from strong A-site ion disorder, which induces large local random electric/stress fields40,41. Under higher voltages (20–30 V), the PFM amplitude responses diverge significantly. The x = 0 sample develops micron-scale FE domains exhibiting strong piezoelectric activity, indicating an electric-field-induced transition from short-range to long-range polar order. In contrast, Sn-doped specimens maintain significantly finer domain configurations, demonstrating that this transition is progressively inhibited with increasing Sn content, which is consisted with our phase-field simulation results. This suppressed domain evolution is directly reflected in the field-dependent polarization responses. As displayed in Figs. 2b and S4, increasing Sn content induces remarkable slimming of P-E loops, coupled with broadening and suppression of current density peaks in current density-field (J–E) curves. It is noted that the current density does not return to zero when the electric field is withdrawn. This is a common feature observed in dielectric and FE materials, which can be understood from the fundamental relationship J ∝ dP/dt = (dP/dE) × (dE/dt)42. Under a triangular voltage waveform, dE/dt value is constant, and dP/dE is proportional to the differential dielectric constant of the material42,43. Thus, a finite background current is a natural manifestation of the material’s intrinsic dielectric polarizability rather than an artifact or a significant loss mechanism42,43. This physical interpretation confirms that the observed non‑zero current does not contradict the low‑energy‑loss characteristics of our ceramics. The optimized x = 0.06 composition achieves significantly improved energy storage performance in bulk ceramic form with Wrec = 8.1 J cm−3 and η = 95.0%, representing 40% and 22% improvements respectively compared to the undoped counterpart. While Wrec decreases slightly with further Sn addition, η remains around 95.0%, likely due to a gradual reduction in Pmax associated with increased non-polar phase content17.

Comparative analysis of field-dependent polarization behavior for two representative compositions (Fig. 2d–g) reveals fundamentally different energy loss mechanisms. The undoped ceramic (x = 0) exhibits pronounced polarization hysteresis under increasing fields, manifested by the rapidly enlarging difference between the total energy storage density Wtotal and Wrec and a dramatic η decrease from 96% to 78% as the field intensifies from 5 to 40 kV mm−1. In striking contrast, the x = 0.06 composition maintains significantly suppressed polarization hysteresis and ultrahigh efficiency (η ≥ 95%) even at 55 kV mm−1, demonstrating superior field stability. Analysis of the dynamic scaling behavior furthers supports this conclusion: the x = 0.06 ceramic exhibits a relatively small exponent α value in its two linear stages compared to the x = 0 ceramic12,28. Moreover, the turning point between these stages occurs at higher electric fields for x = 0.06. These results confirm that Sn4+ introduction effectively suppresses the electric-field-driven growth process from polar nanodomains to micrometer-scale FE domains, resulting in minimal polarization hysteresis even under high electric fields12,28.

The mechanism behind the suppressed field-induced domain evolution was elucidated through multiscale structural characterization. Atomic-resolution energy-dispersive X-ray spectroscopy (EDS) mapping (Fig. 3a) reveals distinct elemental distribution patterns. Primary elements in the lattice, namely A-site cations (Ba, Bi, Ca, and Sr) and B-site Ti, exhibit well-defined periodic distributions consistent with the atomic lattice, indicating a disordered coexistence of multiple elements occupying equivalent lattice sites. In contrast, Na and Sn display a random arrangement with significant intensity fluctuations. The weak signal from Na is related to its low atomic weight, whereas the sparse distribution of Sn is attributed to its low concentration. Although Sn demonstrates macroscopically uniform distribution similar to other elements (Fig. S5), atomic-scale heterogeneity is evident, suggesting local compositional variation and structural non-uniformity. This observation is further supported by the atomic fraction variation of A-site and B-site elements (Figs. S6 and 3a, respectively), where Sn exhibits relatively disordered changes compared to other elements.

Transmission electron microscopy (TEM) analysis of the x = 0.06 ceramic (Fig. 3b) shows no discernible FE domain contrast, indicating the absence of long-range FE order. High-resolution TEM images and corresponding selected-area electron diffraction patterns acquired along the [100]c and [110]c zone axes (Fig. 3c) further confirm the lack of large-scale FE or ferroelastic domains across multiple length scales, supporting the effective disruption of long-range ferroic ordering. To further probe the local polarization configurations, we acquired high-angle annular dark-field (HAADF) images with Z-contrast along the [001]c and [110]c directions (Fig. 3d, e, respectively). Local polarization vectors were mapped by quantifying the displacements of B-site cations relative to their four nearest A-site neighbors, with arrow color and length indicating the direction and magnitude of polarization, respectively. Along the [100]c zone axis (Fig. 3d), the T phase exhibits polarization oriented along [001], while both R and O phases show alignments along [110]. Along the [110]c zone axis (Fig. 3e), the R and O phases are distinguishable by their polarization directions: [111] for R and [110] for O2,15,43. Thus, our analysis reveals localized regions with distinct polar symmetries (R, O, and T). The coexistence of PNRs with multiple FE symmetries reduces polarization anisotropy, implying a low energy barrier for polarization reorientation. This is in favor of realizing a high Pmax. Critically, we identified regions exhibiting near-zero polarization magnitude, which we attribute to nonpolar clusters. These are likely caused by local compositional fluctuations, as supported by intensity variations in the fitted B-site and A-site atomic columns (Figs. 3f, g and S6). Notably, some non-polar nanoclusters (yellow dashed circles in Fig. 3d, e) exhibit enhanced B-site intensity, suggesting Sn-rich regions. The extremely low ionic polarizability of Sn4+ renders these Sn-rich clusters less responsive to electric fields. Furthermore, local unit cells containing Sn4+ coupled with different A-site cations (e.g., CaSnO3, BaSnO3, SrSnO3) are paraelectric with diverse crystal structures. These unit cells not only resist polarization under external fields but also introduce strong random electric and stress fields due to their distinct structural distortions, further suppressing polarization response. Consequently, these confined non-polar nanoclusters effectively inhibit the merging and growth of adjacent PNRs under electric fields, accounting for the extremely low polarization hysteresis observed in our electrical measurements.

MLCCs fabricated with the optimized x = 0.06 composition exhibit exceptional structural and functional integrity. Cross-sectional SEM analysis (Fig. 4a) confirms a well-laminated architecture comprising five highly dense dielectric layers (average thickness ≈ 16 μm) interfaced with continuous metallic electrodes. EDS mapping demonstrates negligible elemental interdiffusion at electrode-dielectric interfaces, preserving interfacial stability. The thickness of different dielectric layers is precisely controlled within a narrow range of ±0.8 μm, ensuring uniform field distribution. Field-dependent polarization responses (Fig. 4b, c) highlight the material’s superior energy storage dynamics. The slim P-E loops exhibit strongly field-amplified Pmax (49.8 μC cm−2 at 108 kV mm−1) with ultralow remnant polarization (Pr < 0.8 μC cm−2), corresponding to hysteresis losses below 8% of total energy input. This behavior directly manifests the effectiveness of the non-polar nanocluster confinement mechanism in suppressing long-range FE ordering under high electric fields while enabling rapid polarization reversal, which is also consistent with the phase-field simulation results. Consequently, a large Wrec of 18.5 J cm−3 and a high η of 92.4% were obtained under 108 kV mm−1 (Fig. 4d). As summarized in Fig. 4e and Table S1 (Supplementary Information), this performance surpasses most recently reported bulk ceramics and MLCCs, demonstrating the exceptional efficacy of our design strategy3–7,9–16,18–30,44–50.

The temperature stability of energy-storage performance is crucial for practical applications7,51,52. Temperature-dependent in-situ Raman spectra (Fig. 5a) reveal minimal changes in peak shape and intensity between 25 and 175°C, indicating temperature-insensitive local structural features49,52. The distinctive broadening and smoothing of Raman peaks at 200°C correlate with reduced unit cell polarity. This remarkable thermal stability is attributed to the complex lattice stress conditions induced by the heterogeneous nanodomains within the material53,54. The variation of capacitance (ΔC/C) at 0.1–10 kHz is less than 15% over a wide temperature between 0 and 250°C (Fig. 5b), further confirming the temperature-insensitive structural features49. Furthermore, the material exhibits suppressed defect mobility at high temperatures. This is evidenced by effectively suppressed high-temperature dielectric loss (tan δ; Fig. 5b), indicating inhibited defect mobility that significantly reduces high-temperature energy losses7,51. Consequently, temperature-dependent P-E loops measured over a broad temperature range (20–170°C) demonstrate exceptional thermal stability, maintaining low hysteresis and high Pmax (Fig. 5c). This results in minimal variations in energy storage parameters (ΔWrec < 2%, Δη < 2%; Fig. 5e). Moreover, across a wide frequency range (1–100 Hz), the MLCCs exhibit outstanding frequency stability (Fig. 5d), characterized by Wrec = 8.9 ± 0.1 J cm−3 and η = 93.4% with variations less than 2% (Fig. 5f).

The charge/discharge performance further confirm the application potential of our MLCCs. Regular underdamped discharge waveforms are observed under electric fields from 20 to 60 kV mm−1 (Fig. 5g). The inset of Fig. 5g shows that the power density (PD) increases with electric field, reaching an ultrahigh value of ≈ 169.9 MW cm−3 at 60 kV mm−1. For overdamped discharge processes, the x = 0.06 MLCC exhibits stable oscillating waveforms from 20 to 60 kV mm−1 with a fixed load resistance (Fig. S8). As shown in Fig. 5h, an ultrahigh discharge energy density (WD) of ≈ 7.4 J cm−3 is achieved at 60 kV mm−1, with 90% of this energy released within ≈ 52.0 ns. This rapid discharge speed is attributed to the fast polarization-field response, as evidenced by the frequency-insensitive P-E loops in Fig. 5d. These comprehensive results demonstrate that the MLCCs exhibit outstanding overall properties with excellent stability, showing promising application prospects for advanced pulse-power capacitors.

In summary, we have demonstrated an effective strategy of non-polar nanocluster confinement engineering to mitigate the long-standing trade-off between Wrec and η in dielectric ceramics via a rationally designed high-entropy BNBSCT1-xSx system. By leveraging phase-field simulations and analyzing multiscale structure evolution, we found that the Sn-riched non-polar nanoclusters within a high-entropy relaxor FE matrix are hardly responsive to external electric fields owing to the weakly FE-active Sn4+ ions and large random fields. These confined nanostructures act as nonpolar pinning centers to inhibit the polar nanodomain mergence during high electric field loading, achieving a collaborative optimization of polarization and hysteresis. The optimized composition yields an excellent energy-storage performance in MLCCs, achieving a Wrec of ~18.5 J cm−3 together with an ultrahigh η of ~92.4%. This represents a competitive combination of properties among state‑of‑the‑art lead‑free counterparts. Our work not only provides a viable design pathway toward high‑efficiency, high‑energy‑density dielectrics for next‑generation power electronics but also offers broader insights into the control of nanoscale polarization behavior in functional materials through local compositional engineering.

Methods
Fabrication of bulk ceramics and MLCCs
The BNBSCT1-xSx perovskite powders were synthesized via a conventional solid-state reaction route employing high-purity precursors (>99%), including BaCO3, CaCO3, SrCO3, Na2CO3, Bi2O3, TiO2, and SnO2. The powders were weighed, thoroughly mixed, and then ball-milled in ethanol using zirconia grinding media for 6 h. The dried mixture was subsequently calcined at 900°C for 8 h in covered alumina crucibles. For bulk ceramic samples, the calcined powders were compacted into pellets and sintered at 1180–1220°C for 2 h within sealed crucibles. For the x = 0.06 MLCC fabrication, the calcined powder with composition x = 0.06 was dispersed in a solvent along with a dispersant and ball-milled for 12 h. Binders and plasticizers were then introduced, followed by additional milling for another 12 h. The resulting slurry was filtered, de-aired, and tape-cast to form green sheets. Ag/Pd electrode paste was screen-printed onto the sheets, which were then stacked, laminated (50°C, 5 min), and subjected to warm isostatic pressing (50 MPa, 55°C) to improve green density. Binder removal was conducted via thermal debinding at 600°C for 2 h with a heating rate of 0.5°C/min. The MLCCs were finally sintered at 1210°C for 2 h.

Structure characterizations
The XRD data were collected on an X-ray diffractometer (D/Max-RB, Rigaku, Japan). The grain morphology of the ceramics was took by a field-emission scanning electron microscope (FE-SEM, SU8020, JEOL, Japan). The domain morphology evolution with bias voltage was performed by using a PFM (Asylum Research MFP‑3D Origin+, Oxford Instruments, UK). Raman spectra was collected on well-polished samples through a Raman spectrometer (LabRam HR Evolution, HORIBA JOBIN YVON, Longjumeau Cedex, France). The atomic-scale STEM HAADF images were performed on a probe-corrected Hitachi HF5000 at 200 kV, while the domain morphology observations and SEAD measurements were carried out on a JEOL JEM-F200 microscope at 200 kV. Specimens for STEM and TEM measurements were prepared by a conventional approach combining mechanical thinning and finally Ar+ ion-milling in a Gatan PIPS II.

Electric property measurements
Temperature/frequency-dependent dielectric properties were measured by an LCR meter (E4980A, Agilent Technologies, Inc., USA) connected with a high/low-temperature probing stage (HCT1821, Tongguo Technology, China). The P-E loops were obtained through an FE measurement system (TF Analyzer 2000E, aixACCT Systems GmbH, Germany). The energy release properties were studied via a charge-discharge platform (CFD-003, Tongguo Technology, China).

Grain size distribution
Grain size distribution was analyzed using Nano Measurer software. To ensure statistical representativeness, the average grain size was determined from a sample of 200 grains, with a relative deviation of less than 5%.

Phase-field simulations
The details of the phase-field simulation about domain structure and polarization configuration are elaborated in the Supplementary Information.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The authors proposed an approach of inducing non-polar nanocluster confinement through the design of a high-entropy (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)(Ti1-xSnx)O3 lead-free relaxor ferroelectrics for energy storage application. The strategy looks good but is not timely. Because the quality of the work does not match with the requirement for a reputed journal like Nat. Comm. since a lot of work is happening in this area and mostly, the scientific community is giving importance to thin film-based capacitors. Also, the energy storage performance parameter values are far lower than values reported for RFE based thin films and simple binary oxide based ultra-thin film capacitors. Therefore, I am sorry to say that work cannot be considered for publication in this journal.", "reviewer_2": "The manuscript of Xie et al., reports a study on lead-free relaxor ferroelectric capacitors based on a high-entropy BNBSCT₁₋ₓSₓ system. The authors propose a “non-polar nanocluster confinement” strategy to address the trade-off between recoverable energy density (Wₚₑc) and energy efficiency (η), supported by phase-field simulations and multiscale structural analysis. Although concept of inhomogeneity introduction with pinning centers is not new, the reported Wrec ≈ 18.5 J•cm⁻³ and η ≈ 92.4% look large for a lead-free dielectric system, and the specific way of using Sn-rich non-polar clusters as pinning centers is potentially useful for designing high-performance dielectrics of this kind. While the topic is certainly relevant to the field of sustainable energy storage and the approach appears interesting, the manuscript in its current form falls short in several important aspects that hinder its scientific impact and clarity. I provide my comments below:\n1) Insufficient Positioning with Respect to State-of-the-Art: The introduction and discussion do not adequately situate the present work within the rapidly evolving state-of-the-art of lead-free relaxor ferroelectrics for capacitive energy storage. For example I found a recent study such of Kang et al., Nat. Commun. (2025) which reports even higher values of Wrec = 19.0 J•cm⁻³, although a bit smaller η = 90%. This work should be cited along with others similar works better in the form of the table demonstrating this paper achievement (for example Ribeiro et al., Nanoscale (2025) reported Wrec = 9.24 J•cm⁻³, η = 86.4%)\n2) Many works exploit nanoscale heterogeneity, therefore, the claimed “breakthrough” performance of the present BNBSCT₁₋ₓSₓ system appears overstated, unless a more rigorous quantitative comparison (under similar field conditions and device formats) is provided.\nA clear benchmarking figure or table comparing the present results to the latest lead-free systems, explicitly differentiating between bulk ceramics, thin films, and MLCC architectures would be a benefit to justify the claim of “superior efficiency”. The authors should temper such claims and clarify the true novelty—perhaps emphasizing more the co-optimization mechanism rather than absolute metrics.\n3) The link between phase-field simulation outputs and experimental observations should be better explained.\n4) Authors should provide the measurement frequency for P-E loops and for Fig. 4S. For this figure (Fig. 4S) authors should also comment on the fact why current J does not go to zero after FE switching for E>20kV/mm.\nMinor Comments\n• Some typos like “sturcture” and stylistic redundancies further obscure the message.\n• The term “breakthrough” should be avoided unless objectively supported by record-setting or unprecedented values.\n• As stated above a graphical comparison to previous works (Wrec vs η plot) would strongly improve readability and credibility.\nI recommend major revision prior to reconsideration. The authors should:\n1. Contextualize their data within the current high-performance literature;\n2. Clarify the unique contribution of their mechanism;\n3. Strengthen experimental and modeling evidence linking structure to function;\n4. Revise language and organization for precision and readability."}, "author_response": "Ruzhong Zuo, Professor\nCenter for Advanced Ceramics\nSchool of Materials Science and Engineering\nAnhui Polytechnic University\nWuhu 241000, China\nzuoruzhong@ahpu.edu.cn\nNov. 3, 2025\nDear Editor\nThank you very much for giving us an opportunity to revise our manuscript entitled “Non-Polar\nNanocluster Confinement Engineering Realizes Exceptional Capacitive Energy Storage in Pb-\nFree High-Entropy Relaxors”. We sincerely thank the reviewers for their time and for providing\ncomments on our manuscript. We have carefully considered the points raised and provide a point-\nby-point response below. We hope that our clarifications and the significant revisions made to the\nmanuscript will adequately address the reviewer's concerns.\nReviewer 1's Comments\nComment 1: The authors proposed an approach of inducing non-polar nanocluster confinement\nthrough the design of a high-entropy (Bi Na Ba Sr Ca )(Ti Sn )O lead-free relaxor\n0.2 0.2 0.2 0.2 0.2 1-x x 3\nferroelectrics for energy storage application. The strategy looks good but is not timely. Because\nthe quality of the work does not match with the requirement for a reputed journal like Nat. Comm.\nsince a lot of work is happening in this area and mostly, the scientific community is giving\nimportance to thin film-based capacitors.\nReply: We thank the reviewer for acknowledging that our strategy “looks good.” Regarding\ntimeliness and quality, we respectfully offer a different perspective based on the current research\nlandscape and the specific contribution of our work.\n Timeliness of the Strategy: The field of lead-free energy storage is indeed rapidly\nevolving. A key contemporary challenge is no longer merely pushing the absolute value\nof energy density (W ) in idealized thin-film systems, but rather designing dielectric\nrec\nmaterials that achieve a superior co-optimization of W and efficiency (η) in scalable,\nrec\npractical forms. Our work addresses this precise challenge by introducing a novel “non-\npolar nanocluster confinement” strategy, which is a timely and active research direction\nfocused on manipulating nanoscale polarization dynamics to overcome intrinsic material\nlimitations.\n Complementarity of Multilayer ceramic capacitors (MLCCs) and Thin Films: We\nagree that thin-film capacitors achieve outstanding performance in laboratory settings.\nHowever, the scientific community invests significant effort in bulk ceramics and MLCCs\nfor a crucial reason: they represent the practically viable pathway for macroscale power\nelectronics due to their superior robustness, scalability, large volume, and cost-\neffectiveness. Thin films and MLCCs are largely complementary technologies serving\ndifferent application spaces. Our work advances the fundamental science and performance\nceiling of the bulk ceramic platform, which remains indispensable.\n Quality and Novelty: The quality of our work is demonstrated through a combined\napproach of phase-field simulation, multiscale structural analysis, and experimental\nvalidation, which provides a comprehensive and mechanistic understanding of the\nstructure-property relationship. This level of fundamental insight into a new material\ndesign strategy meets the high standards for novelty and scientific rigor expected in\nleading journals.\nComment 2: Also, the energy storage performance parameter values are far lower than values\nreported for RFE based thin films and simple binary oxide based ultra-thin film capacitors.\nTherefore, I am sorry to say that work cannot be considered for publication in this journal.\nReply: We agree that the absolute W values of thin films are higher, a direct consequence of\nrec\ntheir nanometer-scale thickness enabling extremely high breakdown fields (>500 kV mm-1).\nHowever, a direct comparison is not equitable due to the fundamental differences in\ndimensionality, fabrication, and application, as noted above.\nThe more relevant and fair comparison is within the category of lead-free MLCCs, which is the\nfocus of our study. Within this context, our reported performance is among the very best,\nparticularly in its combination of high W\nrec\nand ultra-high η:\n Our work achieves W rec ~ 18.5 J cm-3 with an exceptionally high η ~ 92.4%.\n This co-optimization is rare and critically important. Many systems show high W rec at the\nexpense of η (often falling to 80-85%), which leads to significant energy loss and heat\ngeneration in practical devices.\n To contextualize this, we have included a new table (Table S1, Supplementary Information)\nand a W vs. η plot in the revised manuscript, comparing our results with other state-of-\nrec\nthe-art lead-free bulk ceramics, MLCCs and thin films. This visualization clearly shows\nthat our material occupies a leading position in the high-efficiency, high-energy-density\nregion for MLCCs.\nTherefore, we believe the performance of our material is not \"far lower\" in its relevant domain\nbut is, in fact, highly competitive and represents a significant step forward in solving the W -η\nrec\ntrade-off.\n[Table 1 omitted for brevity]\nSummary\nIn summary, we respectfully argue that our work is both timely and of high quality, as it\nintroduces a novel microstructure design strategy to a core problem in the field. It delivers top-\ntier performance within the technologically crucial domain of bulk ceramic and MLCCs,\nsupported by deep physical insight. We have significantly revised the manuscript to better\ncontextualize our work and temper claims, and we hope it is now deemed suitable for publication.\nWe are grateful for the reviewer's feedback, which has helped us improve the presentation of\nour work.\nReviewer 2's Comments\n[Reviewer 2's comments repeated in rebuttal]\nReply: We thank the Reviewer for this critical and valuable suggestion. We agree that a\nmore comprehensive and up-to-date comparison with the state-of-the-art is essential to\nproperly contextualize our work and highlight its significance.\nIn response to this comment, we have taken the following actions:\n1. Citation of Key Recent Works: We have now cited the important and recent works,\nincluding Kang et al., Nature Communications (2025) and the study by Ribeiro et al.,\nNanoscale (2025) in the revised Introduction and Discussion section. This will\nimmediately signal to the reader that our work is positioned within the most current\nresearch landscape.\n2. Inclusion of a Performance Comparison Table: As highly recommended by the\nReviewer, we have added a new table (Table S1, Supplementary Information) and a\nnew figure (Fig. 4e) in the revised manuscript. This table systematically compares the\nenergy storage performance (W and η) of our BNBSCT S capacitors with other\nrec 1-x x\nrecently reported high-performance lead-free bulk ceramics, MLCCs, and thin films,\nincluding the works by Kang et al. and Ribeiro et al. mentioned by the Reviewer.\n[Table 1 repeated in rebuttal]\n3. Enhanced Discussion: In the discussion section, we will now refer to this new table\nand the new Fig. 4e. We will not only list the values but also provide a brief analysis.\nWe will emphasize that while some systems (like Kang et al.) may achieve a\nmarginally higher W , our material achieves a superior combination of both high\nrec\nW (~18.5 J cm-3) and exceptionally high η (~92.4%). This outstanding efficiency is\nrec\na key advantage of our \"non-polar nanocluster confinement\" strategy, as it\nminimizes energy loss, which is crucial for practical applications. This direct\ncomparison will more clearly articulate the specific advancement and niche of our\nwork.\nWe believe these significant revisions will effectively address the Reviewer's concern\nand greatly strengthen the narrative of our manuscript by clearly demonstrating its\ncompetitive position within the forefront of lead-free energy storage material research.\nThanks.\n2) Many works exploit nanoscale heterogeneity, therefore, the claimed “breakthrough”\nperformance of the present BNBSCT S system appears overstated, unless a more rigorous\n1-x x\nquantitative comparison (under similar field conditions and device formats) is provided.\nReply: We sincerely thank the Reviewer for this critical and fair observation. We agree that\nthe term \"breakthrough\" can be subjective and that a more precise and contextualized\ncomparison is necessary to substantiate our claims. We have taken the following concrete\nsteps to address this comment thoroughly:\n1. Tempering Claims and Clarifying Novelty: We have revised the manuscript\nthroughout to remove overstated claims such as \"breakthrough.\" Instead, we now\nmore accurately describe our achievement as \"an excellent combination of high\nrecoverable energy density (Wrec) and ultra-high efficiency (η)\" or \"among the best-\nperforming lead-free bulk ceramics,\" focusing on the co-optimization of these two\nkey parameters, which is a significant challenge in the field. The narrative has been\nreframed to highlight that the true novelty lies in the specific \"non-polar nanocluster\nconfinement\" strategy for effectively achieving this co-optimization, rather than\nsolely in the absolute value of a single metric.\n2. Providing Rigorous, Architecture-Aware Benchmarking: As requested, we have now\nincluded a comprehensive benchmarking table in the revised manuscript (which will\nbe Table S1), explicitly categorizing the reported performance by material\narchitecture (Bulk Ceramics, Thin Films, and MLCCs). This allows for a direct and\nfair comparison with systems under similar conditions and device formats.\n3. Enhanced Discussion Based on Benchmarking: In the discussion section, we now\nrefer to this new table to provide a nuanced analysis. We explicitly state: Our work\nfocuses on MLCCs, and the comparison is primarily made within this category. We\nacknowledge that thin films often achieve higher W due to their ability to withstand\nrec\nmuch higher electric fields, but we emphasize that our work demonstrates superior\nperformance among MLCCs. We reiterate that the key advantage of our MLCC is\nits position in the high-performance landscape, specifically achieving >90%\nefficiency while maintaining a W > 18 J cm-3 under a moderate electric field, a\nrec\ncombination that is rare and highly desirable for practical, low-loss energy storage\ndevices.\nBy implementing these changes, we have provided the rigorous quantitative\ncomparison requested, tempered our language, and sharpened the focus of our manuscript\nonto its core scientific contribution: the material design strategy and the effective co-\noptimization mechanism it enables. We believe the revised manuscript is significantly\nimproved and more scientifically robust.\n3) The link between phase-field simulation outputs and experimental observations should be better\nexplained.\nReply: We sincerely thank the Reviewer for this insightful comment. We fully agree that\ncreating a stronger narrative thread connecting the phase-field simulations presented early\nin the manuscript with the subsequent experimental results is crucial.\nIn our original manuscript, the phase-field simulation in the introduction served as a\ntheoretical prediction and design guide to demonstrate the feasibility of the \"non-polar\nnanocluster confinement\" strategy before experimental synthesis. In response to the\nReviewer's feedback, we have now significantly strengthened the linkage in the following\nways:\n1. Enhanced Discussion in the Results and Discussion Section: We have added a\ndedicated content in the Results and Discussion section that explicitly refers back to\nthe introductory Figure 1 (phase-field simulation). In this new content, we:\no Directly recall the prediction: Remind the reader that our phase-field model\n(Fig. 1) predicted that the introduction of non-polar clusters would lead to a\nslimmer polarization hysteresis, higher breakdown strength, and a more\nuniform polarization distribution under electric fields.\no Confirm the prediction with experiments: We then systematically state that\nour experimental observations—specifically the slimmer P-E loops (Fig. 4)\nand the nanoscale domain structure revealed by PFM and TEM (Fig. 2 and\n3)—are in excellent qualitative agreement with that initial theoretical\nprediction.\no Bridge the gap: We use language such as: \"These experimental results directly\nvalidate the design principle proposed by our phase-field simulations in Fig.\n1, confirming that the Sn-rich non-polar clusters indeed act as effective\npinning centers to confine polar domains and enhance energy storage\nperformance.\"\n2. Improved Narrative Flow: This revision creates a clear \"hypothesis-and-\nverification\" narrative:\no Introduction: \"We propose a strategy... Our phase-field simulations (Fig. 1)\npredict that this strategy will lead to superior properties.\"\no Results/Discussion: \"We synthesized the material... The measured excellent\nperformance (Figs. 4) and observed nanostructure (Fig. 3) experimentally\nconfirm the prediction made in Fig. 1, demonstrating the success of our\ndesign.\"\nWe believe these modifications effectively weave the phase-field simulation into the core\nstory of the paper, transforming it from a standalone design premise into an integral part of\nthe evidence that is explicitly verified by experiments. This greatly clarifies the link between\nsimulation and observation, as requested by the Reviewer.\n4) Authors should provide the measurement frequency for P-E loops and for Fiq.4S. For this figure\n(Fig.4S) authors should also comment on the fact why current does not go to zero after FE\nswitching for E>20kV/mm.\nReply: We thank the Reviewer for these pertinent technical questions and for the\nopportunity to clarify these points.\n1. Measurement Frequency: The Reviewer is correct, and we apologize for this omission.\nThe unipolar P-E loops and the corresponding current-density curves (Fig. 4S in the\nSupplementary Information) were all measured at a frequency of 10 Hz. This\ninformation has now been explicitly added to the Experimental Section/Methods of\nthe main text, as well as in the captions of the relevant figures in the main manuscript\nand the Supplementary Information.\n2. Non-Zero Current after Ferroelectric Switching at High Fields (>20 kV/mm): We\nappreciate the Reviewer's sharp observation regarding the behavior of the current-\ndensity curves in Fig. 4S. The fact that the current does not return to zero after the\nsharp polarization switching peak is a common and expected phenomenon in relaxor\nferroelectric ceramics, especially under high applied electric fields. We have added a\ndiscussion on this point in the Supplementary Information accompanying Fig. 4S.\nThe primary reasons for this are:\no Increased Leakage Current: At high electric fields (approaching the\nmaterial's breakdown strength), the contribution of ohmic leakage current\nbecomes significantly more pronounced. This leakage current, which is\napproximately proportional to the applied field, forms a conductive\n\"background\" upon which the displacement current (from polarization\nswitching) is superimposed. Therefore, even after the polarization switching\nis complete, the measured current does not drop to zero but to a finite value\ncorresponding to this leakage component (Mater. Res. Bull. 2022, 147, 111617).\no Dielectric Relaxation in Relaxor Ferroelectrics: As a canonical relaxor\nferroelectric, our BNBSCT S material contains a high density of polar\n1-x x\nnanoregions (PNRs). The dynamics of these PNRs under a high, rapidly\nchanging electric field involve a broad distribution of relaxation times (J. Adv.\nDielectr. 2011, 01, 107-118; Acta Mater. 2023, 255, 119071). This results in a\nlong-tailed, frequency-dependent dielectric response, which manifests as a\npersistent current after the main switching peak. This is distinct from the\nsharp, square-like current response of a normal ferroelectric.\nIn summary, the non-zero current baseline at high fields is attributed to the combined\neffects of increased leakage current and the intrinsic dielectric relaxation behavior of the\nrelaxor state. This behavior is consistent with other high-performance relaxor ferroelectric\nsystems reported in the literature and is directly linked to the energy loss (and thus the\nefficiency, η) of the material. We thank the Reviewer for prompting us to include this\nimportant physical explanation.\nMinor Comments\n• Some typos like “sturcture” and stylistic redundancies further obscure the message.\nReply: We thank the Reviewer for bringing these language and stylistic issues to our\nattention. We agree that a clear and precise presentation is essential for effective scientific\ncommunication.\nIn response, we have undertaken a thorough revision of the entire manuscript to address\nthese concerns. Specifically, we have:\n1. Corrected All Identified Typos: The typographical error \"sturcture\" has been\ncorrected to \"structure\". We have also performed a meticulous, word-by-word\nproofreading of the entire text to identify and correct any other spelling, grammatical,\nor punctuation errors that may have been overlooked.\n2. Eliminated Stylistic Redundancies: We have carefully reviewed the manuscript for\nredundant phrases, awkward constructions, and unnecessary repetitions. The text\nhas been streamlined to improve clarity, conciseness, and overall readability. For\nexample, we have revised phrases like [\"a large W of 18.5 J·cm-3 and a high η of\nrec\n92.4% were obtained under a high electric field of 105 kV·mm-1,\" -> \"a large W of\nrec\n18.5 J·cm-3 and a high η of 92.4% were obtained under 105 kV·mm-1\"] to ensure the\nmessage is delivered effectively.\n3. Sought Professional Language Editing: To ensure the highest standard of written\nEnglish, the revised manuscript has been professionally proofread by a native\nEnglish-speaking colleague. This step helps to eliminate subtle linguistic errors and\nfurther polish the academic writing style.\nWe believe these comprehensive efforts have significantly improved the clarity and\nprofessionalism of the manuscript's presentation, ensuring that the scientific message is no\nlonger obscured by language issues.\n• The term “breakthrough” should be avoided unless objectively supported by record-setting or\nunprecedented values.\nReply:We thank the Reviewer for reinforcing this important point. We fully agree with the\nneed for precise and measured language. In line with our detailed response to Comment #2,\nwe have systematically removed the term \"breakthrough\" and other similar superlatives\nthroughout the revised manuscript. The claims are now tempered, and the novelty is more\naccurately framed in terms of the effective co-optimization of energy density and efficiency\nachieved through our specific material design strategy.\n• As stated above a graphical comparison to previous works (Wrec vs η plot) would strongly\nimprove readability and credibility.\nReply:We thank the Reviewer for this excellent suggestion. In full agreement, and as a direct\nextension of the new benchmarking table (addressing Comment #2), we have now included\na new figure (Fig. 4e: W vs. η plot) in the revised manuscript.\nrec\nThis plot provides an immediate, visual representation of the performance landscape\nfor lead-free MLCCs, clearly highlighting the position of our BNBSCT S material in the\n1-x x\nhigh-efficiency, high-energy-density region. We believe this graphical comparison\nsignificantly enhances the readability and impact of our performance analysis, as suggested.\nI recommend major revision prior to reconsideration. The authors should:\n1. Contextualize their data within the current high-performance literature;\nReply: We fully agree with this point. In direct response to the Reviewer's specific comments,\nwe have now provided a dual-faceted benchmarking against the state-of-the-art:\n We have added a detailed table (Table S1,) in the Supporting Information that\nquantitatively compares our performance (W , η) with other recent high-\nrec\nperformance lead-free systems, explicitly differentiating between bulk ceramics, thin\nfilms, and MLCCs.\n Furthermore, we have included a new graphical plot (Fig. 4e: W rec vs. η) that offers\nan immediate visual representation of the performance landscape, clearly situating\nour work in the high-efficiency, high-energy-density region for bulk ceramics.\nThese additions ensure our claims are now rigorously supported and contextualized.\n2. Clarify the unique contribution of their mechanism;\nReply:We have substantially tempered our language and refined the narrative to clarify the\nunique contribution. As requested, we have removed overstated terms like \"breakthrough.\"\nThe revised manuscript now unambiguously frames the novelty not solely on absolute\nmetrics, but on the effectiveness of our \"non-polar nanocluster confinement\" strategy in\nachieving a superior co-optimization of W and η. We emphasize that this specific design\nrec\napproach, validated by multiscale evidence, is the key mechanistic insight.\n3. Strengthen experimental and modeling evidence linking structure to function;\nReply: This is a crucial point, and we have strengthened this link in several ways. Primarily,\nwe have created a much tighter connection between the phase-field simulations and\nexperimental data:\n We now explicitly discuss how the simulated slimmer P-E loops and confined\nnanoclusters predict the macroscopic behavior we observe experimentally.\n The discussion directly correlates the simulation outputs with our experimental P-E\nloops, current-density curves, and nanoscale structural analysis (e.g., TEM and\nPFM), creating a coherent \"prediction-to-verification\" narrative that solidifies the\nstructure-property relationship.\n4. Revise language and organization for precision and readability.\nReply: We have undertaken a comprehensive language edit to address this. This includes:\n Correcting all typographical errors (e.g., \"sturcture\" -> \"structure\").\n Eliminating stylistic redundancies and streamlining the text for clarity.\n Explicitly stating key experimental parameters previously omitted (e.g., the\nmeasurement frequency of 10 Hz for P-E loops).\n The manuscript has been professionally proofread to ensure a high standard of\nwritten English.\nWe are confident that these revisions have thoroughly addressed all the Reviewer's\nconcerns and have greatly enhanced the scientific rigor, clarity, and impact of our work. We\nare grateful for the opportunity to resubmit an improved manuscript."}, {"round": 2, "reviewer_comments": {"reviewer_1": "Thank you, for the response to my comments. However, I am still not satisfied with the authors response to the reason for the rejection from a reputed journal like Nat. comm. The author presented a comparison table for the recently reported work and their work cannot overcome the performance matrices. For instance, the energy storage performance reported in this work is comparable with the works reported in ref [32], [36] and [38]. Moreover, there are reported works on clustering the ferroelectric domains in the nanoscale region through disrupting long range FE order or forming nano-domains and refining grains in MLCC [https://www.nature.com/articles/s41467-025-64113-7]. So, I am sorry to say that my final decision is either transfer or rejection.", "reviewer_2": "In general, the authors have satisfactory revised the manuscript; however, I still have concerns regarding the claimed of 'Exceptional' capacitive energy storage and the manuscript's suitability for this particular journal. In principle, there is novelty and improvement, but I suggest changing the title to replace 'Exceptional' with 'High' (or a similar term). In my opinion, the reported improvement is not 'Exceptional.' Also I have searched, but found no mention of 10 Hz for the FE loop cycles frequency as stated in the rebuttal letter. The explanation for the non-zero current due to leakage conflicts with the low-energy loss claimed by the authors. This non-switching component in the FE current may actually stem from parasitic capacitance in the circuit or from multi-scale capacitance subsystems within the sample. I also suggest sorting Table S1 according to efficiency parameters rather than presenting it in a random manner."}, "author_response": "Ruzhong Zuo, Professor\nCenter for Advanced Ceramics\nSchool of Materials Science and Engineering\nAnhui Polytechnic University\nWuhu 241000, China\nzuoruzhong@ahpu.edu.cn\nDec. 5, 2025\nDear Editor\nThank you very much for giving us an opportunity to revise our manuscript entitled “Non-Polar\nNanocluster Confinement Engineering Realizes Exceptional Capacitive Energy Storage in Pb-\nFree High-Entropy Relaxors”. We sincerely thank the reviewers for their time and for providing\ncomments on our manuscript. We have carefully considered the points raised and provide a point-\nby-point response below. We hope that our clarifications and the significant revisions made to the\nmanuscript will adequately address the reviewer's concerns.\nReviewer 1's Comments\nComment 1: Thank you, for the response to my comments. However, I am still not satisfied with\nthe authors response to the reason for the rejection from a reputed journal like Nat. comm. The\nauthor presented a comparison table for the recently reported work and their work cannot\novercome the performance matrices. For instance, the energy storage performance reported in this\nwork is comparable with the works reported in ref [32], [36] and [38].\nReply:We sincerely appreciate Reviewer 1's continued involvement and valuable feedback.\nWe have carefully reflected on the comment regarding our work's performance relative to\nthe cited references, and we would like to further clarify the scope and positioning of our\ncontribution.\nIndeed, the field of dielectric energy storage ceramics has progressed remarkably in\nrecent years, with numerous high-quality studies published. In compiling our comparative\nanalysis (Table S1), we intentionally focused on what we regard as the most influential and\ntop-performing works in the field—those that represent seminal advances and set current\nbenchmarks. These selected studies reflect the leading strategies employed to overcome\nlongstanding challenges in ceramic energy storage. Within this rigorous framework, we are\npleased to note that the overall energy storage performance demonstrated in our work\nremains strongly competitive, as clearly illustrated in Fig. 4e. This positions our material\namong the forefront of reported systems and underscores the efficacy of our proposed\nstrategy.\nBeyond quantitative metrics, we also believe that a study's significance is substantially\nshaped by the conceptual novelty and mechanistic depth it provides. In this context, our\nwork introduces a distinct design approach: the use of confined non-polar nanoclusters\nwithin a relaxor ferroelectric matrix to reconcile the inherent conflict between polarization\nenhancement and hysteresis reduction—a long-standing trade-off in the field. Supported by\nintegrated theoretical and experimental evidence, this strategy not only delivers compelling\nperformance but also provides a new conceptual framework that may guide future material\ndesign beyond incremental improvements.\nWe hope this clarification helps to better situate our contribution within the current\nresearch landscape.\nComment 2: Moreover, there are reported works on clustering the ferroelectric domains in the\nnanoscale region through disrupting long range FE order or forming nano-domains and refining\ngrains in MLCC [https://www.nature.com/articles/s41467-025-64113-7]. So, I am sorry to say\nthat my final decision is either transfer or rejection.\nReply: We sincerely thank the reviewer for raising this important point and for sharing the\nrelevant reference. We wish to clarify that the study cited by the reviewer has already been\nreferenced in our manuscript, and we have explicitly acknowledged in the Introduction the\nsignificant progress made in the field through the engineering of polar nanoregions/clusters.\nOur work, however, is fundamentally centered on a conceptually distinct strategy: the\ndeliberate introduction and stabilization of non-polar nanoclusters within the relaxor\nmatrix. While polar nanoregions—as utilized in prior works—do contribute to reduced\nhysteresis at low and moderate fields, they remain susceptible to electric-field-induced\nmerging and growth under higher fields, which ultimately limits their effectiveness in\nmaintaining high efficiency. In contrast, the Sn-rich non-polar clusters in our system, owing\nto the low polarizability of Sn4+ and the formation of local paraelectric units, remain largely\nunresponsive to electric fields. These inert clusters serve as spatially confined pinning\ncenters that physically impede the coalescence and growth of polar domains, especially\nunder high electric fields, thereby suppressing hysteresis without compromising maximum\npolarization.\nThis conceptual distinction is clearly articulated throughout our manuscript: it is\nreflected in the title, which emphasizes the \"non-polar nanocluster confinement\" strategy;\nit is framed in the Abstract and Introduction as a departure from conventional polar-centric\napproaches; and it is systematically validated in the Results and Discussion. We therefore\nbelieve that our work offers a novel and complementary pathway to decoupling high\npolarization from low loss—one that moves beyond the established paradigm of polar\nheterogeneity and represents a meaningful step forward in the design of high-performance\ndielectric materials.\nReviewer 2's Comments\nComment 1: In general, the authors have satisfactory revised the manuscript; however, I still have\nconcerns regarding the claimed of 'Exceptional' capacitive energy storage and the manuscript's\nsuitability for this particular journal. In principle, there is novelty and improvement, but I suggest\nchanging the title to replace 'Exceptional' with 'High' (or a similar term). In my opinion, the\nreported improvement is not 'Exceptional.'\nReply: We sincerely thank the reviewer for the thorough assessment and constructive\nsuggestions, which have helped us further improve the manuscript.We fully agree with the\nreviewer and have revised the title accordingly. The term “Exceptional” has been replaced\nwith “High” to more accurately and objectively reflect the performance level achieved. The\nupdated title now reads: “Non-Polar Nanocluster Confinement Engineering Realizes High\nCapacitive Energy Storage in Pb-Free High-Entropy Relaxor Ferroelectrics”\nComment 2: Also I have searched, but found no mention of 10 Hz for the FE loop cycles\nfrequency as stated in the rebuttal letter.\nReply: We apologize for this oversight. The measurement frequency of 10 Hz for the P-E\nloops has now been explicitly stated in in the corresponding figure captions where relevant.\nComment 3: The explanation for the non-zero current due to leakage conflicts with the low-\nenergy loss claimed by the authors. This non-switching component in the FE current may actually\nstem from parasitic capacitance in the circuit or from multi-scale capacitance subsystems within\nthe sample.\nReply: We sincerely thank the reviewer for raising this insightful point regarding the non-\nzero current observed in our J-E curves. We apologize for the oversimplification in our\nprevious response and have since conducted a thorough re-evaluation of the underlying\nphysics. Based on a careful review of the relevant literature and fundamental principles, we\nwould like to provide a more accurate explanation.\nThe phenomenon is not primarily due to increased leakage current under high fields or\nparasitic capacitance. Instead, it arises from the fundamental relationship between the\npolarization current and the material's dielectric constant. In unipolar P-E testing with a\ntriangular voltage waveform (Fig. R1), the current density (J) is derived from the time\nderivative of the polarization (P), which is directly related to the derivative of polarization\nwith respect to the electric field (dP/dE). As established in prior studies (e.g., J. Phys. D: Appl.\nPhys. 34, 3279–3284 (2001); Ceramics International 30, 1389–1392 (2004)), the displacement\ncurrent can be expressed as J  dP/dt = (dP/dE) * (dE/dt). Because a triangular waveform\nimposes a constant dE/dt value, the measured current density J becomes directly\nproportional to dP/dE, which in turn reflects the differential dielectric constant (ε ) of the\nd\nmaterial.\n[Fig. R1 omitted]\nCrucially, ε (and thus the intrinsic dielectric polarizability) remains finite even when\nd\nthe external electric field is withdrawn to zero (i.e., at E = 0, ε  0). Consequently, the\nd\npolarization current does not-and should not-return to zero at the end of a half-cycle; a finite\ncurrent background is a natural and expected feature of the dielectric response. This\nexplains why the J-E curves presented in our work, as well as those in the vast majority of\nreports on dielectric and ferroelectric materials, consistently exhibit this characteristic. The\nphenomenon is widely observed, though it is seldom explicitly discussed in the literature.\nThus, the non-zero current in our measurements is a normal feature that reflects the\ncontinuous dielectric polarizability of the material, rather than an artifact or a significant\nloss mechanism. We have clarified this point in the revised manuscript to avoid any\nmisunderstanding and to provide a more physically rigorous interpretation. This correction\nstrengthens our discussion and confirms that the ultrahigh efficiency (η > 92%) is fully\nconsistent with the intrinsic low-loss behavior of our ceramics.\nWe are grateful to the reviewer for prompting this deeper clarification, which has\nimproved the accuracy of our work. The relevant description has been modified in text in\nred (Page 6).\nI also suggest sorting Table S1 according to efficiency parameters rather than presenting it in a\nrandom manner.\nReply:We thank the reviewer for this helpful suggestion. Table S1 has been reorganized and\nis now sorted in descending order of energy efficiency (η%), making it easier for readers to\ncompare performance trends across different studies.\nWe believe that these revisions have addressed all the reviewer’s concerns and have\nfurther enhanced the clarity and accuracy of the manuscript. Thank you once again for the\nvaluable feedback."}, {"round": 3, "reviewer_comments": {"reviewer_2": "I somehow tend to agree with the referee 1. While manuscript now seems to be technically correct, its novelty looks insufficient with respect to other works and the journal score. I have no more questions and leave the final decision to the Editor."}, "author_response": "Ruzhong Zuo, Professor\nCenter for Advanced Ceramics\nSchool of Materials Science and Engineering\nAnhui Polytechnic University\nWuhu 241000, China\nzuoruzhong@ahpu.edu.cn\nDec. 25, 2025\nDear Editor\nThank you very much for giving us an opportunity to revise our manuscript entitled “Non-Polar\nNanocluster Confinement Engineering Realizes High Capacitive Energy Storage in Pb-Free High-\nEntropy Relaxors”. We sincerely thank the reviewers for their time and for providing comments\non our manuscript. We have carefully considered the points raised and provide a point-by-point\nresponse below.\nReviewer 2's Comments\nI somehow tend to agree with the referee 1. While manuscript now seems to be technically correct,\nits novelty looks insufficient with respect to other works and the journal score. I have no more\nquestions and leave the final decision to the Editor.\nReply: We sincerely thank Reviewer 2 for their time and valuable assessment of our manuscript.\nWe appreciate the reviewer’s acknowledgment of the technical correctness of the work.\nRegarding the comment on novelty, we respectfully wish to highlight several key innovative\naspects of our study that may not have been fully emphasized:\n1. Strategy Innovation: We introduce a “non-polar nanocluster confinement” strategy,\nconceptually distinct from common approaches that focus solely on polar nanostructure\nmodulation. This is achieved by deliberately creating localized non-ferroelectric\nperovskite units within a high-entropy relaxor matrix to act as immobile pinning centers.\n2. Material Design Paradigm: The work synergistically combines high-entropy composition\ndesign with targeted ion substitution (Sn4+) guided by phase-field simulations. This\nsimulation-guided design to stabilize specific non-polar clusters within a high-entropy\nenvironment presents a novel methodology for property optimization.\n3. Mechanistic Insight: We provide a clear physical rationale—stabilized by inherent high-\nentropy random fields—for why these non-polar clusters effectively suppress polar\ndomain growth without being switched themselves, directly addressing the classic\npolarization–hysteresis trade-off.\n4. Performance Benchmark: The achieved combination of a high recoverable energy density\n(~18.5 J·cm-3) and a large efficiency (~92.4%) in a lead-free multilayer ceramic capacitor\nrepresents a competitive advance among state-of-the-art lead-free systems, as validated in\nthe manuscript.\nWe believe the integration of this novel strategy, the guided design process, and the resultant\nperformance collectively constitute a meaningful step forward in the field of dielectric energy\nstorage.\nThank you once again for your constructive feedback. We have incorporated all previous\nsuggestions and hope the manuscript in its current form is now suitable for publication.\nSincerely,\nProf. Ruzhong Zuo (the corresponding author)"}]

Decision letter