High‐entropy (HE) oxides have become increasingly popular as electromagnetic wave‐absorbing materials owing to their customizable structure and unique HE effects. However, the weak loss property of single‐phase HE ceramics and the approaches implemented to improve them based on semi‐empirical rules severely limit their development. Herein, two biphasic HE oxides are prepared by simple sintering to realize accurate regulation of crystal phases and structural defects. It is verified that HE effects cause various defects that are beneficial for microwave dissipation within complex‐phase ceramics. In spinel/perovskite HE oxides, around the interface of spinel (111) and perovskite (110) planes, notable stress concentrations and lattice distortions are directly observed, inducing numerous point defects and stacking faults. Interestingly, besides the existing heterogeneous interface of rock salt (220)/spinel (220) plane and defects, rock salt/spinel HE oxides enabled synergistic effects via the precise regulation of components’ phase. Driven by structural defects and multi‐phases in HE complexes, the intense polarization is evidently found, confirmed by the first‐principles calculations. Accordingly, the two complex‐phase HE oxides demonstrate excellent microwave absorption performance, and the minimal reflection loss of −54.5 dB is achieved. Therefore, this study provides valuable guidelines for the design of microwave absorbers using HE oxides.

The addition of numerous main metal elements into highentropy alloys (HEAs) have been popular since their discovery in 2004. [2] This has provided a vast combinatorial space for the exploration of new materials with unexplored abnormal functionalities. In general, four core factors, namely, sluggish diffusion, configurational entropy, lattice distortion, and cocktail effects, affect the crystal structure and properties of HEAs. [3] Since 2015, the concept of high entropy has been successfully expanded to include oxides. [4] Similar to HEAs, high-entropy oxides (HEOs) are defined as compositions consisting of oxygen and more than five metal cations in equimolar or near equimolar ratios in the range of 5-35% atomic concentration. [5] HEOs are rapidly emerging as delicate functional constituents that offer excellent compositional flexibility that permits the stabilization of numerous compositions with various crystal structures (e.g., rock-salt, spinel, fluorite, perovskite, and pyrochlore phases). [6] Consequently, HEOs present numerous attractive functional properties, such as high ionic conductivity; [7] superior storage capacity retention and good stable cycles of Li battery; [8] low thermal conductivity and good thermal stability; colossal dielectric constant; [9] and novel magnetic phenomena. [10] However, a deep understanding of their microstructures has yet to emerge. Thus, it is extremely urgent to learn more about the microstructure of HEOs to further understand their anomalous 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 (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Pb 0.2 )TiO 3 perovskite is reported, and the effective absorption bandwidth (90% absorption) improves almost two times than that of BaTiO 3 . 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.

Hydrogels exhibit potential applications in smart wearable devices because of their exceptional sensitivity to various external stimuli. However, their applications are limited by challenges in terms of issues in biocompatibility, custom shape, and self-healing. Herein, a conductive, stretchable, adaptable, self-healing, and biocompatible liquid metal GaInSn/Ni-based composite hydrogel is developed by incorporating a magnetic liquid metal into the hydrogel framework through crosslinking polyvinyl alcohol (PVA) with sodium tetraborate. The excellent stretchability and fast self-healing capability of the PVA/liquid metal hydrogel are derived from its abundant hydrogen binding sites and liquid metal fusion. Significantly, owing to the magnetic constituent, the PVA/liquid metal hydrogel can be guided remotely using an external magnetic field to a specific position to repair the broken wires with no need for manual operation. The composite hydrogel also exhibits sensitive deformation responses and can be used as a strain sensor to monitor various body motions. Additionally, the multifunctional hydrogel displays absorption-dominated electromagnetic interference (EMI) shielding properties. The total shielding performance of the composite hydrogel increases to ~ 62.5 dB from ~ 31.8 dB of the pure PVA hydrogel at the thickness of 3.0 mm. The proposed bioinspired multifunctional magnetic hydrogel demonstrates substantial application potential in the field of intelligent wearable devices.

Core–shell nanostructures have received widespread attention because of their potential usage in various technological and scientific fields. However, they still face significant challenges in terms of fabrication of core–shell nanostructure libraries on a controlled, and even programmed scale. This study proposes a general approach to systematically fabricate core–shell nanohybrids using liquid‐metal Ga alloys as reconfigurable templates, and the initiation of a local galvanic replacement reaction is demonstrated utilizing an ultrasonic system. Under ultrasonic agitation, the hydrated gallium oxides generated on the liquid metal droplets, simultaneously delaminated themselves from the interfaces. Subsequently, single‐metal or bimetallic components are deposited on fresh smooth Ga‐based alloys via galvanic reactions to form unique core–shell metal/metal nanohybrids. Controlled and quantitative regulation of the diversity of the non‐homogeneous nanoparticle shell layer composition is achieved. The obtained core–shell nanostructures are used as efficient microwave absorbers to dissipate unwanted electromagnetic wave pollution. The effective absorption bands (90% absorption) of core–shell GaNi and GaCoNi nanohybrids are 3.92 and 3.8 GHz at a thickness of 1.4 mm, respectively. This general and advanced strategy enables the growth of other oxides or sulfides by spontaneous interfacial redox reactions for the fabrication of functional materials in the future.

Recently, to improve the applicability of transition-metal carbon/nitride (MXene) shielding devices by integrating with nanomaterials and polymers has gradually attracted the attention of researchers. Although the addition of insulation enhancement...