Dielectric ceramic capacitors are promising for pulsed-power electronics owing to their high power density and rapid charge−discharge, yet their wider application is limited by a relatively low recoverable energy density (W_rec) and difficulty in simultaneously achieving high W_rec and high energy efficiency (η). Herein, a relaxor-to-superparaelectric crossover is engineered in NaNbO₃–(Bi_0.5K_0.5)TiO₃–BaZrO₃ multilayer ceramics, yielding an impressive W_rec of ~16.5 J·cm⁻³, a superior η of ~96.2% and a large W_rec/E merit value of 206.3 J·(kV)⁻¹·mm⁻². Multiscale structural analysis reveals that the introduced (Bi_0.5K_0.5)TiO₃ and BaZrO₃ stabilize the ferroelectric phase, disrupt long-range polar order, and shift the dielectric permittivity maximum close to room temperature, collectively creating a relaxor–superparaelectric transitional state composed of heterogeneous polar nanoregions (PNRs) with diverse symmetries and sizes. These PNRs exhibit highly dispersive reorientation dynamics under electric fields and thus enable high maximum polarization and simultaneously minimum hysteresis, accounting for the concurrent enhancement in both W_rec and η. Furthermore, the broad thermal stability range of this transitional state leads to excellent temperature-insensitive performance from 25 to 150 °C (W_rec = 8.5 J·cm ±3.2%, η = 96.1%±2.8%). This work demonstrates a viable material strategy for engineering relaxor–superparaelectric crossover to develop high-performance dielectric ceramics for advanced energy storage.

Dielectric capacitors exhibiting high energy-storage properties and excellent pulse performance are critical components in advanced pulsed power systems. Multilayer ceramic capacitors (MLCCs) are the most widely used capacitors due to their high integration and excellent high-temperature endurance. Nevertheless, achieving high energy density and reliable performance over a wide temperature range and prolonged cycling remains the major challenge for existing commercial MLCCs based on linear dielectrics or Pb-based antiferroelectrics. Herein, we developed BaTiO₃-based relaxor ferroelectric MLCCs with X9S characteristics for high-voltage applications. The BaTiO₃-based MLCCs exhibit a good energy density of 6.09 J cm⁻³ and an ultrahigh efficiency of 98.2%, with superior stability in temperature (< 10%, 24–250 °C) and fatigue (after 10⁶ cycles, < 4% at 200 °C). The pulse properties of MLCCs show minimal variation (< 4.5%, 22–200 °C). Moreover, 6878-size MLCCs with 300 nF can release a peak current of 3600 A at a rated voltage of 3000 V, which exhibits higher peak currents than linear MLCCs and better stability than Pb-based MLCCs. The excellent performance and superior stability demonstrate that relaxor ferroelectric MLCCs have great potential for advanced energy storage and pulsed power applications.

Dielectric pulse capacitors are of great concerns due to the fast charge/discharge rate and high-power density over traditional counterparts. However, energy-storage capacitor in power converters typically works at a large DC-biased voltage, where the energy-storge density (W_dis) and efficiency (η) will dramatically decay, thus fatally blocks its further applications. Herein, we proposed a synergistic strategy to achieve a comprehensively improved energy storage property in Bi_1-xNa_xTiO₃-NaNbO₃ based ceramics. Configuration of chemical composition optimization, A-site vacancy engineering, grain size refinement, and sample thickness reduction were designed in the ceramics. Finally, an optimum W_dis of 8.04 J/cm³ and an ultrahigh η of 85% was achieved for the 0.50 (0.95Bi_0.52Na_0.44TiO₃-0.05SrZrO₃)-0.50NaNbO₃ composite under a breakdown strength of 630 kV/cm, along with a stable DC-biased capacitance retention. Additionally, a superior performance stability was affirmed in a wide temperature/frequency range (25–150 ℃ and 1–100 Hz, respectively). It also exhibits an impressive ability in fatigue resistance after being subjected to up to 10⁶ cycles, which enable it to be a suitable candidate for high energy density storage devices.

The disruption and reconstruction of the TREM2⁺ tissue resident macrophage (TRM) barrier on the surface of synovial lining play a key role in the activation and "remission" of rheumatoid arthritis (RA), which engender the prediction of this immunologic barrier as a potential driver for the achievement of "cure" in RA. However, strategies to promote the reconstruction of this barrier have not been reported, and the effect of patching this barrier remains unidentified. On the other hand, appropriate piezoelectric stimulation can reprogram macrophages, which has never been exerted on this barrier TRM yet. Herein, we design piezoelectric tetragonal BaTiO₃ (BTO) ultrasound-driven nanorobots (USNRs) by the solvothermal synthesis method, which demonstrates satisfactory electro-mechanical conversion effects, paving the way to generate controllable electrical stimulation under ultrasound to reprogram the barrier TRM by minimally invasive injection into joint cavity. It is demonstrated that the immunologic barrier could be patched by this USNR effectively, thereby eliminating the hyperplasia of vessels and nerves (HVN) and synovitis. Additionally, TREM2 deficiency serum-transfected arthritis (STA) mice models are applied and proved the indispensable role of TREM2 in RA curing mediated by USNR. In all, our work is an interesting and important exploration to expand the classical tetragonal BTO nanoparticles in the treatment of autoimmune diseases, providing a new idea and direction for the biomedical application of piezoelectric ceramics.

There has been great progress in the last decade in the synthesis of nanopowders with highly controlled size and size distribution. Meanwhile, the development of an unconventional pressureless two-step sintering strategy enabling densification without grain growth provides a novel technology suitable for commercial production of nanograin ceramics. The particular interest concerning bulk dense nanograin ceramics is the manifestation of ferroelectricity, which remains a fundamental issue to be understood and exploited. Combining the best powder synthesis and optimized two-step sintering, high-density barium titanate (BT) and related nanograin ceramics have been fabricated to allow for a detailed determination of the size effect on nanometer-scale ferroelectricity and piezoelectricity of fundamental and industrial interest. These include dense ceramics of undoped BT with an average grain size down to 5 nm, and of (1−x)BiScO₃−xPbTiO₃ (BSPT) solid solutions with an average grain size down to 10 nm. Here we review the fabrication methods of high-density BT and BSPT nanoceramics and the major findings of the size effect on their microstructure, phase transition and electrical properties. Robust ferroelectricity is demonstrated for the first time in 5 nm BT nanoceramics, while strong local piezoelectricity is present in 10 nm BSPT nanoceramics.