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Recently, Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) single crystals present tremendous potential in optical applications such as Q-switches and invisible robotic devices because they possess high electro-optic properties and perfect transparency simultaneously. However, due to the difficulties in testing and sample preparation, the nonlinear optical properties of PMN-PT single crystals have not been reported yet, which poses a bottleneck for exploring its nonlinear application. In this work, a large second-order nonlinear coefficient (d31 ∼ 77.9 pm V−1) of single domain PMN-0.39PT single crystal has been revealed, which is times times higher than the maximum nonlinear coefficient of commercial LiNbO3 single crystal (d33 = 25.4 pm V−1). The complete set of nonlinear coefficients of the sample has been determined by second harmonic generation microscopy. This work presents the promising nonlinear optical property in PMN-PT single crystals and opens a door for designing high-performance nonlinear optical devices. [ABSTRACT FROM AUTHOR]

Alternating current polarization (ACP) has been demonstrated to enhance the performance of 1-3 piezoelectric single crystal composites (PSCCs), compared to direct current polarization (DCP). However, the scaling effect and temperature stability of PSCCs under different polarization modes, which are of significance to practical applications, have rarely been studied. Here, we compared and analyzed the thickness and temperature-dependent properties of PSCCs under ACP and DCP. The results indicated that ACP PSCCs have improved piezoelectric, electromechanical coupling, and dielectric properties. There were scaling effects for PSCCs with thickness below 400 μm. Compared to high-thickness PSCCs, the piezoelectric coefficient (d33), free dielectric constant ( ε 33 T ε 0 ) as well as thickness electromechanical coupling factor (kt) of low-thickness samples were inferior and the corresponding performance enhancements under ACP were also relatively low. In contrast, the clamped dielectric constant ( ε 33 S ε 0 ) did not show significant thickness correlation. As for temperature stability, all performances of PSCCs improved with increase in temperature and the performance enhancement with temperature change was not dependent on the polarization conditions. This work provides reference significance of selecting appropriate polarization for PSCCs, thus benefiting the design and preparation for transducers. [ABSTRACT FROM AUTHOR]

Over the past decades, lead-based relaxor ferroelectrics have served as the model systems to unravel the relationship between electromechanical properties and local structure. Here, by employing pair distribution function analysis and the reverse Monte Carlo method, we investigate the local structural features and their temperature dependence in relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-xPbTiO3 with x = 0.15 (PZN-15PT), which has a tetragonal average structure, but displays frequency dependence at low temperatures. The refined atomic model suggests that ordered polar nanoregions (PNRs) originate from the strong atomic displacive correlation, and their polar directions are the same as the crystallographic symmetry axis. The dipoles in the disordered matrix have weak correlations and can be averaged into a global tetragonal symmetry. These findings establish a detailed picture of the local structure of lead-based relaxor ferroelectrics and provide a deeper insight into the nature of PNRs. [ABSTRACT FROM AUTHOR]

Pb-based relaxor piezoelectric single crystal composites (PSCCs) have attracted widespread attention for improving the bandwidth and sensitivity performance of acoustic transducers due to their excellent electromechanical and piezoelectric properties. Alternating current polarization (ACP) has been proven as an effective method for enhancing the dielectric and piezoelectric properties of relaxor-PbTiO3 single crystals. Herein, we investigated the effects of the amplitude, frequency, and cycle number of the poling electric field on the piezoelectric and dielectric performances of PSCCs and obtained the optimum poling condition of ACP. Compared with the traditional direct current poling method, both the dielectric permittivity ( ε 33 T / ε 0 ) and piezoelectric coefficient ( d 33 ) of the AC-poled PSCCs were both increased by up to 20%. Notably, the ACP PSCC with a volume fraction of 60% exhibited a high d 33 of 1610 pC/N, which is superior to values previously reported for PSCCs. This work provides an alternative strategy for enhancing the properties of PSCCs and may contribute to the further development of piezoelectric applications. [ABSTRACT FROM AUTHOR]

High-temperature piezoelectric devices require piezoelectric ceramics with high Curie temperatures and high-temperature stability of piezoelectric properties to avoid the depolarization of piezoelectric ceramics during application. However, piezoelectric materials with high Curie temperatures usually have restrained piezoelectric properties. Crystallographic orientation via texture engineering is a practicable way to improve piezoelectric performance. Here, we propose a sintering-aid-assisted template grain growth strategy to texture BiScO3-PbTiO3 ceramics to overcome the low orientation issue that challenges the texturing of BS-PT for decades. By judiciously selecting B2O3-CuO as sintering aids, we fabricated highly ⟨001⟩-textured 0.43BS-0.57PT ceramics with Logtering factors >99.0% that possess high piezoelectric coefficients d33 of 474–612 pC/N while maintaining relatively high Curie temperatures of 370–402 °C. Importantly, this work addresses a long-standing issue presented in BS-PT ceramics, i.e., the low electromechanical coupling property of BS-PT ceramics (k33 < 0.70) by improving the electromechanical coupling factor k33 to 81.2%. The newly designed textured BS-PT ceramics are thought to be promising candidates for the design of high-temperature piezoelectric transducers and actuators. [ABSTRACT FROM AUTHOR]

AgNbO3 (ANO)-based lead-free antiferroelectric ceramics with high energy storage density show potential application in pulsed power systems. Structural heterogeneity via doping different ions offers an effective route to explore high performance dielectric materials. The effect of A-site and B-site modified ANO-based ceramics at the same doping amount of 50% on ferroelectricity was investigated. The result shows that the A/B site structural heterogeneities both improved relaxor features, which make a great contribution to the energy storage efficiency, while the B-site modification shows a more effective influence on the structure, grain growth, and ferroelectricity regulation. In this case, the optimized recoverable energy storage density of 2.6 J/cc with an improved efficiency of 87.6% was achieved in the Ta-ANO component. [ABSTRACT FROM AUTHOR]

Various wireless sensors in the Internet of Things (IoT) systems have been adopted in ocean exploration, with increasing energy supply concern. Regarding the marine environment, self-powered sensors utilizing ambient flow and wave energy can increase maintainability with a long lifespan. However, the current underwater piezoelectric energy harvesters made of piezoelectric ceramics suffer from low power density (<0.5 mW cm−3 m−1 s). In this paper, we proposed a vortex-induction underwater piezoelectric energy harvester based on a Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) single crystal macro-fiber composite (MFC). The single crystal MFC shows mechanical flexibility in which the volume fraction of the piezoelectric phase is 70%. Regarding the structure design, a bicylinder configuration with a ladder-shaped cantilever is employed for decreasing the resonant frequency of the underwater piezoelectric energy harvester and enhancing vortex force during fluid–structure interaction process. The designed underwater energy harvester exhibits a high output voltage of 54 Vpp at 0.9 m/s flow in the designed underwater energy harvesting test platform. Due to the high figure-of-merit d 32 × g 32 (7.65 × 10−11 m2/N) of the single crystal, the maximum output power reaches 62 μW under the flow speed of 0.9 m/s. The normalized power density is 1.1 mW cm−3 m−1 s, being 2.3 times larger than that of the state-of-the-art PZT ceramics-based underwater energy harvester. This work will help to mitigate the energy crisis of the IoT system, promoting the development of underwater equipment. [ABSTRACT FROM AUTHOR]

In this letter, we report on significant flexoelectric fatigue in lead-free (K,Na,Li)(Nb,Sb)O3 (KNNLS) ceramics. In the ferroelectric phase of KNNLS, the observed effective transverse flexoelectric coefficient, which is initially as high as 1 μC/m, decreases nonlinearly with increasing cycles of strain gradient, and the fatigue regulation is well reproduced by a stretched exponential function. By comparing the time dependence of dielectric permittivity and ferroelectricity in KNNLS ceramics, we conclude that large flexoelectric and flexocoupling coefficients in the ferroelectric phase originate mainly from ferroelectricity and that the related flexoelectric fatigue is likely due to the pinning effect of ferroelectric domains. [ABSTRACT FROM AUTHOR]

Over the past decades, lead-based relaxor ferroelectrics have served as the model systems to unravel the relationship between electromechanical properties and local structure. Here, by employing pair distribution function analysis and the reverse Monte Carlo method, we investigate the local structural features and their temperature dependence in relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-xPbTiO3 with x = 0.15 (PZN-15PT), which has a tetragonal average structure, but displays frequency dependence at low temperatures. The refined atomic model suggests that ordered polar nanoregions (PNRs) originate from the strong atomic displacive correlation, and their polar directions are the same as the crystallographic symmetry axis. The dipoles in the disordered matrix have weak correlations and can be averaged into a global tetragonal symmetry. These findings establish a detailed picture of the local structure of lead-based relaxor ferroelectrics and provide a deeper insight into the nature of PNRs. [ABSTRACT FROM AUTHOR]

The temperature dependence of the shear piezoelectric responses in relaxor-PbTiO3 based perovskite crystals with rhombohedral, orthorhombic, and tetragonal phases were investigated. Based on thermodynamic analysis, high shear piezoelectric coefficients (d24) and good thermal stability were predicted in orthorhombic crystals, owing to the 'vertical' orthorhombic-rhombohedral phase boundary. By resonance measurements, shear piezoelectric coefficient d24 was found to be on the order of ∼2100 pC/N at room temperature, maintaining same value over the temperature range of -50-100 °C. In contrast, the shear piezoelectric coefficients d15, with values of 3300, 3600, and 2000 pC/N at room temperature for rhombohedral, orthorhombic, and tetragonal crystals, respectively, exhibited strong temperature dependent behavior due to their respective ferroelectric-ferroelectric phase transitions. [ABSTRACT FROM AUTHOR]

The piezoelectric properties of Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals with various engineered domain configurations were investigated. Rhombohedral and monoclinic/orthorhombic crystals poled along their crystallographic [011] directions were found to possess macroscopic mm2 symmetry, with '2R' and '1O' domain, respectively. Crystals with the '2R' domain configuration were found to exhibit high extensional piezoelectric coefficients d33 (∼1300 pC/N) and d32 (∼-1680 pC/N), while crystals with the '1O' configuration possessed high shear coefficients d15 (∼3500 pC/N) and d24 (∼2070 pC/N), with relatively low extensional piezoelectric coefficients d33 (∼340 pC/N) and d32 (∼-260 pC/N). The observed results were explained by 'polarization rotation' model, as related to their respective domain configurations. [ABSTRACT FROM AUTHOR]

Organic photodetectors have attracted increasing attention in the scenario of low-cost imaging, health monitoring, and near-infrared sensing. However, relatively high dark current and trap density block the sensitivity for organic photodetectors. In this manuscript, a simple yet effective strategy is proposed to enhance the detectivity of organic photodetectors by incorporating a non-conjugated polymer additive of polystyrene into the functional layers. Systematic morphological investigation reveals that this strategy can not only enable suppressed amorphous phase but also effectively tune the phase separation in the bulk heterojunction blends. Electrical results suggest the suppressed trap density in optimized organic photodetectors. Consequently, a dark current density of 5.06 × 10−10 A cm−2 is achieved for PM6:Y6-BO-based organic photodetectors, showing a peak detectivity of 6.38 × 1013 cm Hz1/2 W−1 at 850 nm. This strategy is also applicable in various representative organic-semiconductor systems, including PTB7-Th:PC71BM and P3HT:PC61BM blends, superior to other optimization techniques. [ABSTRACT FROM AUTHOR]

This study presents an investigation into the stress effect on the leakage current in ferroelectric Al 0.7 Sc 0.3 N films by experiments and density functional theory (DFT) computations. The experiments are based on 8-in. 100 nm Al 0.7 Sc 0.3 N films obtained from pulsed DC co-sputter deposition technology, which exhibit non-uniform compressive in-plane stress across the wafers and similar distributions of leakage current, suggesting close dependence between each other. DFT computations revealed that stress affects leakage current in two ways: the level of traps introduced by nitrogen vacancy and the formation energy of nitrogen vacancy in Al 0.7 Sc 0.3 N. By considering both factors, the leakage current of Al 0.7 Sc 0.3 N films increases with larger compressive in-plane stress, as observed in the experimental results. Additionally, the DFT calculation results indicated that the leakage current is more sensitive to compressive stress compared to the tensile, and the minimum leakage current can be obtained with neutral in-plane stress. These findings provide a guideline for stress engineering to optimize the AlScN-based ferroelectric devices. [ABSTRACT FROM AUTHOR]

We demonstrate a long-wavelength infrared quantum cascade detector (QCD) that operates at a wavelength of 10 μm, in which the active diagonal transition for the electrons occurs from a fundamental energy level into a miniband in adjacent coupled quantum wells. When compared with a bound-to-bound diagonal transition-based QCD, the use of a miniband as the final transition state increases the absorption strength and enhances the electron extraction efficiency of the device, leading to QCD responsivities of 75 at 180 and 30 mA/W at 300 K for 10.55 μm wavelength operation. [ABSTRACT FROM AUTHOR]

In this work, a helical structure with three spiral channels is employed to build the coding units of metalenses, which can provide high transmission efficiency with an arbitrary phase shift compared to air. The helical unit with the phase shift of π is used as logical unit 1, and the hollow tube filled with air is regarded as logical unit 0. By arranging these logical units in specific sequences, acoustic metalenses can achieve wave-field manipulation like acoustic focusing and splitting. The focusing efficiency as high as 41.5% is achieved. Meanwhile, the genetic algorithm is applied to seek the optimal arrangement of the bipartite units for 3D sound focusing. Simulations and experiments are conducted to demonstrate the proposed coding metalenses for molding the acoustic wave field in the desired manners. [ABSTRACT FROM AUTHOR]