A boom in exploration for marine geology and ocean resources has resulted in a huge demand for radio navigation or special environment communications, in turn spurring the rapid development of portable underwater wireless communication technology. State of the art acoustic communication methods used today are plagued by substantial transmission delays, multipath effects, and doppler frequency shifts, among other challenges, thus impeding the advancement of underwater wireless communication technology. Low-frequency electromagnetic transmission has proven to be a prospective solution for underwater communication, but the conventional electrical antennas is too large for portable underwater wireless communication. Emergent magnetoelectric (ME) antennas driven by piezoelectric materials have become a promising solution for miniaturizing very low frequency (VLF) communication systems. Here, a theoretical model between the radiation performance and piezoelectric material properties of the ME antenna was conducted. Guide by the theory analysis, Pb(In_1/2Nb_1/2)O₃–Pb(Mn_1/3Sb_2/3)O₃–Pb(Zr_0.49Ti_0.51)O₃ (PIN-PMS-PZT) piezoelectric ceramic simultaneous with high d₃₃ and Q_m (d₃₃ ~ 401, Q_m ~ 1510) has been designed to enhance the magnetoelectric radiation of the VLF ME antenna. The PIN-PMS-PZT based ME antenna achieves a large converse magnetoelectric response 1.78 Gs·cm/V in EMR, which is almost doubled to commercial PZT based ME antenna. More importantly, a VLF communication system was built based on the VLF antenna, which successfully transmitted digital signals using Amplitude-Shift-Keying (ASK) modulation. It is believed that the presented work could provide a theoretical basis and feasible technical path for the employment of ME antennas in the future.

High piezoelectric properties and low strain hysteresis (H) are both equally necessary for practical applications in precisely controlled piezoelectric devices and systems. Unlike most of previous reports, where enhanced piezoelectric performance is typically accompanied by large hysteresis in lead-/lead-free-based ceramics, in this work, we report a reconstructed relaxor ferroelectric composition in 0.68Pb(Mg_1/3Nb_2/3)O₃–0.32PbTiO₃ (0.68PMN–0.32PT) ceramics through the introduction of (Bi_0.5Na_0.5)ZrO₃ (BNZ) to simultaneously achieve low strain hysteresis (~7.68%), superior piezoelectricity (~1040 pC·N⁻¹), and an electric field induced strain of 0.175%. Our work not only paves the way to simultaneously large piezoelectricity and negligible strain hysteresis in ceramic systems, but also lays the foundation for the further development of novel functional materials.

Piezoelectric materials are widely used in sensors and actuators due to their unique electromechanical coupling capability. However, the tradeoff between flexibility and high piezoelectric performance restrains their application into flexible electronic technology, which is an important underpinning for the future intelligent technology. In this review, we summarized the flexible piezoelectric materials currently available and their design and preparation strategies. Also, the application of flexible piezoelectric materials in pressure sensing, energy harvesting and biomedicine was outlined. Finally, we gave the challenges and perspectives of developing the flexible piezoelectric materials.

Intelligent robots have assisted mankind in achieving and operating thousands of functions, especially with the arrival of the artificial intelligent. However, heat dissipation and thermal management in the intelligent robots remain big challenges, which limit their miniaturization and performance. Electrocaloric (EC) materials, which exhibit temperature change in response to the application or withdrawal of an electric field, open a new strategy for cooling technology and have gained a flurry of research interest in recent years. Toward artificial intelligent self-cooling electronic skins, large-scale flexible materials with high EC effect near room temperature are in demand. Here, we report a large room temperature EC effect in flexible Pb_0.82Ba_0.08La_0.1Zr_0.9Ti_0.1O₃ (PBLZT) inorganic thin films via a transfer-free cost-effective sol-gel process, assisted by unique two-dimensional mica substrates. The maximum adiabatic temperature change and isothermal entropy change of the flexible PBLZT thin films reach to 22.5 K and 25.9 J K^{− 1} kg^{− 1} at room temperature. In particular, the flexible PBLZT thin films exhibit a stable EC effect both under bending state and after bending for 20000 times. Our flexible EC materials offer an alternative strategy to the development of cooling technologies for both artificial intelligent robots and personal wearable cooling devices.