High‐entropy oxides (HEOs), which incorporate multiple‐principal cations into single‐phase crystals and interact with diverse metal ions, extend the border for available compositions and unprecedented properties. Herein, a high‐entropy‐stabilized (Ca0.2Sr0.2Ba0.2La0.2Pb0.2)TiO3 perovskite is reported, and the effective absorption bandwidth (90% absorption) improves almost two times than that of BaTiO3. The results demonstrate that the regulation of entropy configuration can yield significant grain boundaries, oxygen defects, and an ultradense distorted lattice. These characteristics give rise to strong interfacial and defect‐induced polarizations, thus synergistically contributing to the dielectric attenuation performance. Moreover, the large strains derived from the strong lattice distortions in the high‐entropy perovskite offer varied transport for electron carriers. The high‐entropy‐enhanced positive/negative charges accumulation around grain boundaries and strain‐concentrated location, quantitatively validated by electron holography, results in unusual dielectric polarization loss. This study opens up an effective avenue for designing strong microwave absorption materials to satisfy the increasingly demanding requirements of advanced and integrated electronics. This work also offers a paradigm for improving other interesting properties for HEOs through entropy engineering.

High‐Entropy Enhanced Microwave Attenuation in Titanate Perovskites

The miniaturization of electronic devices and power systems for capacitive energy storage under harsh environments requires scalable high‐quality ultrathin high‐temperature dielectric films. To meet the need, ultrasonic spray‐coating (USC) can be used. Novel polyimides with a dipolar group, CF3 (F‐PI), and all‐organic composites with trace organic semiconductor can serve as models. These scalable high‐quality ultrathin films (≈2.6 and ≈5.2 µm) are successfully fabricated via USC. The high quality of the films is evaluated from the micro‐millimeter scale to the sub‐millimeter and above. The high glass transition temperature Tg (≈340 °C) and concurrent large bandgap Eg (≈3.53 eV) induced by weak conjugation from considerable interchain distance (≈6.2 Å) enable F‐PI to be an excellent matrix delivering a discharge energy density with 90% discharge efficiency Uη90 of 2.85 J cm−3 at 200 °C. Further, the incorporation of a trace organic semiconductor leads to a record Uη90 of ≈4.39 J cm−3 at 200 °C due to the markedly enhanced breakdown strength caused by deep charge traps of ≈2 eV. Also, a USC‐fabricated multilayer F‐PI foil capacitor with ≈85 nF (six layers) has good performance at 150 °C. These results confirm that USC is an excellent technology to fabricate high‐quality ultrathin dielectric films and capacitors.

Scalable Ultrathin All‐Organic Polymer Dielectric Films for High‐Temperature Capacitive Energy Storage

Enhanced capacitive energy storage and dielectric temperature stability of A-site disordered high-entropy perovskite oxides

Achieving high energy storage properties in perovskite oxide via high-entropy design

Owing to the high power density, eco-friendly, and outstanding stability, the lead-free ceramics have attracted great interest in the fields of pulsed power systems. Nevertheless, the low energy storage density of such ceramics is undoubtedly a severe problem in practical applications. To overcome this limitation, the lead-free ceramics with gradient structures are designed and fabricated using the tape-casting method herein. By optimizing the composition and distribution of the gradient-structured ceramics, the energy storage density, and efficiency can be improved simultaneously. Under a moderate electric field of 320 kV cm-1 , the value of recoverable energy storage density (Wrec ) is higher than 4 J cm-3 , and the energy storage efficiency (η) is of ≥88% for 20-5-20 and 20-10-20. Furthermore, the gradient-structured ceramics of 20-10-0-10-20 and 20-15-0-15-20 possess high applied electric field, large maximum polarization, and small remnant polarization, which give rise to ultrahigh Wrec and η on the order of ≈6.5 J cm-3 and 89-90%, respectively. In addition, the energy storage density and efficiency also exhibit excellent stability over a broad range of frequencies, temperatures, and cycling numbers. This work provides an effective strategy for improving the energy storage capability of eco-friendly ceramics.

Wenlong Si

Papers

High-entropy enhanced capacitive energy storage