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BaTiO3(BT)‐templated 0.5Pb(Ni1/3Nb2/3)O3–0.16PbZrO3–0.34PbTiO3 with 0.2 wt% Li2CO3 (PNN‐PZT + LC) ceramics were successfully sintered at temperatures less than 1050°C. Their structural, ferroelectric, and piezoelectric properties were systematically investigated as a function of amount of BT, which ranged from 2 to 10 vol%. The PNN‐PZT + LC ceramics sintered at 1000°C showed highly textured morphologies with preferred (0 0 1) orientation, having Lotgering factors (fL) of 85% and higher. When sintering temperature exceeded 1000°C, the epitaxial grain growth of PNN‐PZT + LC rhombohedral phase, driven by BT templates, was hindered by dramatically enlarged matrix grains. In situ X‐ray diffractometry analyses are performed to identify phase transition behavior depending on temperature. Properties of d33 (1180 pC/N) and kp (80.3%) were obtained for the 2 vol% BT‐templated PNN‐PZT + LC ceramic sintered at 1000°C, along with ferroelectric properties of 2Pr (56.1 μC/cm2) and 2Ec (1.26 kV/mm) at 3.5 kV/mm. High‐resolution transmission electron microscopy and piezo‐response force microscopy were utilized to investigate domain structure and epitaxial grain growth between templated BaTiO3 and matrix ceramics. The low‐temperature sintered specimen showed an extremely large electrostrain characteristic (d33*) of 1215 pm/V at 1 kV/mm. Furthermore, textured multilayer piezoelectric actuators exhibited higher actuator performance and lower energy loss compared to untextured multilayer piezoelectric actuators, indicating their potential for use in piezoelectric actuator devices. [ABSTRACT FROM AUTHOR]

Flexible piezoelectric sensors have been spotlighted as an essential human–machine interface (HMI) by obtaining high‐quality data from omnipresent biomechanical inputs. Because human voice is the most intuitive bio‐signal among them, flexible piezoelectric acoustic sensors (f‐PAS) have a potential to shift the paradigm of HMI technologies. Despite the reported outstanding performance such as high sensitivity and speaker recognition accuracy, the theoretical investigation of f‐PAS has been insufficient to realize future customized development, because sensing principles are fundamentally different from commercialized microphones. Here, a theoretical framework of self‐powered f‐PAS by using mechanical and electrical physics is introduced. First of all, the basic theory of f‐PAS is compared with the auditory system of human cochlear. Based on the biomimetic trapezoidal shape, the resonant frequencies are analyzed with various structural and material conditions. In addition, the piezoelectricity of f‐PAS is derived to predict the sensitivity and SNR prior to experiments. To investigate sensor properties under the medium condition that is similar to human ear, the acoustic responses depending on the states of matter are theoretically compared. Finally, the distance limit of f‐PAS is studied with the correlations between piezoelectricity and sound pressure, which would provide novel strategies of functional material design for future applications of f‐PAS. [ABSTRACT FROM AUTHOR]

The lack of theoretical understanding of triboelectrification has hindered the development of energy harvesting technologies like triboelectric nanogenerators. Focusing on polytetrafluoroethylene, a material with a strong triboelectric output, a model predictive of its triboelectric behavior, driving the development of improved nanogenerators are formulated. With a combined computational‐experimental approach it is shown that defluorination enhances polytetrafluoroethylene nanoscale triboelectric charging. Then a model, explaining the macroscale triboelectric output as determined by the competition of two mechanisms is developed. Defluorination enhances charging while also reducing the interface gap, favoring the backflow of electrons, and possibly reducing charging. However, numerical analysis shows that backflow is negligible, aligning with the prediction of increased triboelectric output. By building triboelectric nanogenerators with defluorinated polytetrafluoroethylene samples, achieved by X‐ray irradiation, a one‐order‐of‐magnitude output increase is demonstrated. The predictive models, supported by experiments, lead to an improved strategy for designing effective energy harvesting devices and new applicative breakthroughs. [ABSTRACT FROM AUTHOR]

Dielectric materials are highly desired for pulsed power capacitors due to their ultra-fast charge-discharge rate and excellent fatigue behavior. Nevertheless, the low energy storage density caused by the low breakdown strength has been the main challenge for practical applications. Herein, we report the electric energy storage properties of (1 − x) Bi0.5(Na0.8K0.2)0.5TiO3-xBi0.2Sr0.7TiO3 (BNKT-BST; x = 0.15–0.50) relaxor ferroelectric ceramics that are enhanced via a domain engineering method. A rhombohedral-tetragonal phase, the formation of highly dynamic PNRs, and a dense microstructure are confirmed from XRD, Raman vibrational spectra, and microscopic investigations. The relative dielectric permittivity (2664 at 1 kHz) and loss factor (0.058) were gradually improved with BST (x = 0.45). The incorporation of BST into BNKT can disturb the long-range ferroelectric order, lowering the dielectric maximum temperature Tm and inducing the formation of highly dynamic polar nano-regions. In addition, the Tm shifts toward a high temperature with frequency and a diffuse phase transition, indicating relaxor ferroelectric characteristics of BNKT-BST ceramics, which is confirmed by the modified Curie-Weiss law. The rhombohedral-tetragonal phase, fine grain size, and lowered Tm with relaxor properties synergistically contribute to a high Pmax and low Pr, improving the breakdown strength with BST and resulting in a high recoverable energy density Wrec of 0.81 J/cm3 and a high energy efficiency η of 86.95% at 90 kV/cm for x = 0.45. [ABSTRACT FROM AUTHOR]