Abstract Lead-free relaxor ferroelectric ceramic is suitable for pulse energy storage. Achieving both high energy storage density and efficiency is crucial for the research. Herein, (1-x)(0.5Sr0.7Bi0.2TiO3-0.5K0.5Bi0.5TiO3)-xNaTaO3 relaxor ferroelectric ceramic is fabricated to optimize microstructures and energy storage behavior based on multi-sites charged defects synergistic regulation engineering. Na+ doping in A-site contributes to polymorphic polarization; Ta5+ doping in B-site refines grain and increases the electrical resistance; the formation and migration process of oxygen vacancy charged defects are significantly suppressed in O-site based on ion doping and the formation of Bi2Ti2O7-based insulating phase. The introduction and synergistic regulation of these charged defects enhance the ionic and charge disorder and configurational entropy, and induces more small-sized polar structure, resulting in the enhanced relaxor ferroelectricity and delayed polarization saturation. Meanwhile, the micromorphology is improved, resulting in the enhanced electrical insulation. Consequently, the polarization and breakdown behavior are optimized. 0.9(0.5Sr0.7Bi0.2TiO3-0.5K0.5Bi0.5TiO3)-0.1NaTaO3 exhibits low remnant polarization, high breakdown strength and maximum polarization, and achieves high energy storage density of 5.68 J/cm3 with high efficiency of 88.1% at moderate operating electric fields 490 kV/cm, and excellent temperature (-50~150 °C), frequency (10~500 Hz), and cycling stability. Meanwhile, the sample shows good pulsed charging-discharging properties with thermal stability and long cycle life (105 cycles at 25 °C and 150 °C). Therefore, this sample demonstrates promising potential for pulse energy storage, and this study offers a novel strategy and mechanism for the designing and optimization of advanced energy storage ceramics.
Abstract Developing flexible electronics that integrate multimodal sensing, bias-free signal generation, and electromagnetic interference (EMI) shielding is critical for wearable health monitoring, artificial intelligence, and human-computer interaction. Semiconducting Mo2TiC2Tx MXene films show promise for flexible thermoelectrics and EMI shielding, but their relatively low electrical conductivity restricts both the power factor (PF) and the overall EMI shielding effectiveness (SE). Here, we report a van der Waals heterostructure film of Mo2TiC2Tx/TaS2, fabricated via intercalation-exfoliation followed by vacuum-assisted filtration. The heterointerface engineering simultaneously enhances thermoelectric performance and EMI shielding. The electricalconductivity reaches 878.3 S cm−1 (~23-fold enhancement), and the PF reaches 14.4 μW m−1 K−2 (~4-fold), while the EMI SE improves from 14.1 to 40.6 dB. The film enables dual-mode sensing free from crosstalk, temperature detection via the Seebeck effect and pressure sensing via piezoresistive response, as well as maintaining stable signal fidelity under external EMI. Furthermore, the film exhibits photothermoelectric and Joule-heating responses. Integrated with a wireless acquisition module for signal readout and transmission, the sensor enables real-time transmission of temperature and pressure signals. This work provides a strategy for designing flexible heterostructures that synergistically combine bias-free signal generation, multimodal sensing, EMI resilience, and multi-stimulus responsiveness for next-generation smart electronics.
Abstract Refractory BaZrO3-based protonic ceramics offer outstanding chemical stability for protonic ceramic electrochemical cells but require sintering temperatures exceeding 1550 °C because of sluggish cation diffusion, leading to detrimental Ba volatilization, electrode coarsening, and microstructural degradation. Here, we report low-temperature processing of BaZr0.8Y0.2O3-δ (BZY) at only 1350 °C though a cooperative interfacial co-sintering strategy enabled by defect-structure coupling across the electrolyte/support interface. Zinc incorporation increases oxygen-vacancy concentration and is accompanied by enhanced sintering kinetics within the BZY electrolyte, while a Ni-modified BCZYYb support promotes cooperative membrane densification. Electron paramagnetic resonance and X-ray photoelectron spectroscopy confirm enhanced oxygen-vacancy formation, while the reduced thermal budget suppresses Ba evaporation and Ni coarsening, producing a fully dense electrolyte with a proton conductivity of ~0.01 S cm-1 at 550 °C. The resulting cells deliver reversible electrochemical operation with electrolysis current densities reaching -4 A cm-2 at 1.5 V and exceptional durability, exhibiting an ohmic degradation rate of only 0.012% h-1. This work establishes a defect-chemistry-guided, scalable processing strategy for overcoming diffusion-limited sintering in refractory protonic ceramics and provides a broadly applicable route toward low-temperature manufacturing of advanced solid-state electrochemical devices.
Abstract Electrically conductive composite ceramics face a critical trade-off where increasing the phase domain size ratio between the insulating matrix and the conductive phase theoretically enhances conductivity but practically hinders densification. The resulting porosity inevitably degrades both mechanical and electrical properties. To address this limitation, a matrix particle size grading strategy is proposed using the Al2O3–TiC system as a model. The incorporation of nano-Al2O3 into a micro-Al2O3 matrix triggers a synergistic microstructural evolution. Specifically, nano-Al2O3 particles fill interparticle spaces to promote densification and may pin TiC grain boundaries, thereby contributing to the refinement of the conductive phase domains. Concurrently, the micro-Al2O3 phase domains coarsen at the expense of nano-Al2O3, maximizing the phase domain size disparity and favoring the formation of a continuous three-dimensional TiC network. With 10 vol% nano-Al2O3 addition, the calculated effective percolation threshold drops from 15.54 vol% to 10.20 vol%, achieving an electrical conductivity of 4.02 × 104 S/m. Consequently, the composite exhibits enhanced electrical discharge machining (EDM) performance, achieving a material removal rate of 9.50 mm2/min alongside high surface quality. This strategy offers a robust framework for developing advanced conductive ceramics tailored for EDM applications.
Multi-principal component diboride (MEB) ceramics are promising candidates for ultrahigh-temperature thermal protection systems. However, their intrinsic oxidation behavior above 2000 u00B0C remains poorly understood because conventional testing methods have limitations. Here, an ultrafast heating oxidation test (UHOT) with a heating rate of 100 u00B0C/s was applied to investigate the oxidation behavior of (Zr1/4Hf1/4Ta1/4Ti1/4)B2, (Zr1/4Hf1/4Ta1/4Nb1/4)B2, (Zr1/3Hf1/3Ta1/3)B2, and monolithic ZrB2 ceramics at 2300 u00B0C under cyclic oxidation conditions. After five 1-min cyclic exposures at this temperature, totaling 5 min, MEB ceramics form multi-layered oxide scales, while ZrB2 ceramic develops only a porous and cracked single-layer scale. Among them, the Ti-containing composition exhibits the thinnest scale, the densest outer layer, the least mass loss, and intact scale integrity. Beyond the thermodynamic contribution of configurational entropy, this superior performance mainly arises from the dual role of the functional element Ti. First, it forms a liquid Ti-containing oxide phase that densifies the outer (Zr,Hf)O2-based layer derived from the structural elements Zr and Hf, enabling the outer layer to act as an effective oxygen diffusion barrier. Second, it promotes the formation of a porous needle-like Ta2O5 network in the inner layer during cooling, which can relieve thermal stress and prevent interfacial separation during cyclic heating and cooling. This work establishes a rapid-heating evaluation protocol and shows that oxidation resistance in these materials is governed by elemental functionality rather than entropy alone, offering a design principle for both equimolar and nonequimolar multiprincipal component nonoxide ceramics for reusable thermal protection applications.
