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High-performance piezoelectrics benefit transducers and sensors in a variety of electromechanical applications. The materials with the highest piezoelectric charge coefficients (d33) are relaxor-PbTiO3 crystals, which were discovered two decades ago. We successfully grew Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Sm-PMN-PT) single crystals with even higher d33 values ranging from 3400 to 4100 picocoulombs per newton, with variation below 20% over the as-grown crystal boule, exhibiting good property uniformity. We characterized the Sm-PMN-PTon the atomic scale with scanning transmission electron microscopy and made first-principles calculations to determine that the giant piezoelectric properties arise from the enhanced local structural heterogeneity introduced by Sm3+ dopants. Rare-earth doping is thus identified as a general strategy for introducing local structural heterogeneity in order to enhance the piezoelectricity of relaxor ferroelectric crystals. [ABSTRACT FROM AUTHOR]

Abstract: Long‐range ordering of dipoles is a key microscopic signature of ferroelectrics. These ordered dipoles form ferroelectric domains, which can be reoriented by electric fields. Relaxor ferroelectrics are a type of ferroelectric where the long‐range ordering of dipoles is disrupted by cation disorder, exhibiting complex polar states with a significant amount of local structural heterogeneity at the nanoscale. They are the materials of choice for numerous devices such as capacitors, nonlinear optical devices, and piezoelectric transducers, owing to their extraordinary dielectric, electro‐optic, and electromechanical properties. However, despite their extensive applications in these devices, the origins of their unique properties are yet to be fully understood, hindering the design and exploration of new relaxor ferroelectric‐based materials. Herein, the complex polar states and applications of relaxor ferroelectrics are first introduced. Attention is then focused on their electromechanical properties, where the relationship between local structural heterogeneity and the extraordinary electromechanical properties is discussed. Based on the understanding of relaxor ferroelectrics, potential strategies to exploit the local structural heterogeneity to design ferroelectrics for drastically enhancing their electromechanical performances are also discussed. It is expected that this article will stimulate future studies on the important roles of local structural heterogeneity in improving the properties of various functional materials. [ABSTRACT FROM AUTHOR]

Perovskite ferroelectrics (PFs) have been the dominant piezoelectric materials for various electromechanical applications, such as ultrasonic transducers, sensors, and actuators, to name a few. In this review article, the development of PF crystals is introduced, focusing on the crystal growth and piezoelectric activity. The critical factors responsible for the high piezoelectric activity of PFs (i.e., phase transition, monoclinic phase, domain size, relaxor component, dopants, and piezoelectric anisotropy) are surveyed and discussed. A general picture of the present understanding on the high piezoelectricity of PFs is described. At the end of this review, potential approaches to further improve the piezoelectricity of PFs are proposed. [ABSTRACT FROM AUTHOR]

Flexoelectricity yields electric polarization through graded strains and exists in various kinds of solid dielectrics but usually with a weak coupling response. In this letter, several Bi-doped Pb(Mg2/3Nb1/3)O3-xPbTiO3 (PMN-xPT) ferroelectric ceramics were prepared and the interplay of their piezoelectricity and flexoelectricity was systematically investigated. The largest flexoelectric response (∼300 μC/m) was 30 times larger than that of pure PMN-PT and was observed in the Bi-doped PMN-32PT, where the after poling piezoelectric coefficients were also the largest (990 pC/N) among all the compositions. This suggests that the apparent flexoelectricity in ferroelectrics is highly related to the bulk piezoelectricity. Therefore, introducing a local structural heterogeneity is considered as a feasible approach to achieve an ultrahigh piezoelectric response while also providing an ultrahigh flexoelectricity. [ABSTRACT FROM AUTHOR]

Compared with the state-of-the-art Pb(Zr,Ti)O3 ceramics, relaxor-PbTiO3 (PT) based ferroelectric single crystals possess much higher piezoelectricity, thus receiving considerable attention from the ferroelectric community. Recently, it was found that the alternating current electric field poling (AC-poling) could further improve the piezoelectricity of [001]-poled rhombohedral (R) relaxor-PT single crystals. In this work, we investigated the domain structures and electromechanical properties of alternating current electric field poled (AC-poled) relaxor ferroelectric Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) crystals with different orientations and phase structures, including [001]-oriented R PIN–PMN–PT (23/47/30), [011]-oriented R PIN–PMN–PT (23/47/30), and [001]-oriented monoclinic (MC) PIN–PMN–PT (22/44/34) single crystals. We found that the piezoelectric coefficient (d33), free dielectric permittivity (ɛ33T/ɛ0), and clamped dielectric permittivity (ɛ33S/ɛ0) for AC-poled [001]-oriented R PIN–PMN–PT (23/47/30) crystals were improved by 24.4%, 22.6%, and 8.5%, respectively, when compared with the direct current electric field poled (DC-poled) counterparts. This phenomenon is attributed to the increase of domain size according to the observations from polarized light microscopy. Nevertheless, for [011]-poled R PIN–PMN–PT and [001]-poled MC PIN–PMN–PT crystals, the dielectric permittivities and piezoelectric coefficients were decreased a bit by AC-poling, being attributed to the depolarization phenomenon caused by the AC electric field. This work demonstrates that impacts of AC-poling on the properties of ferroelectrics are highly related to the orientation and phase of ferroelectric crystals. [ABSTRACT FROM AUTHOR]

The low uniformity in properties of relaxor ferroelectric crystals is a long‐standing issue in the ferroelectric community, which limits the available volume of the entire crystal boule. The aim of this study is to develop a relaxor ferroelectric crystal with improved property uniformity and excellent piezoelectricity. To this end, Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 is doped with Nd2O3 (Nd–PIN–PMN–PT) to improve the crystal performance. Along the crystal boule, the piezoelectric coefficient d33 varies from 2800 to 3500 pC N−1, and the dielectric constant ranges from 8400 to 9800, with variations of 25% and 16%, respectively. Such high property uniformity results in over 75% available volume of the crystal boule, compared to 30–50% for undoped crystals grown by Bridgman method. At the electric field of 1 kV cm−1, the converse piezoelectric response is up to 4780 pm V−1. In addition, its Curie temperature (TC) and coercive field (EC) are above 150 °C and 3 kV cm−1, respectively. Compared with Pb(Mg1/3Nb2/3)O3–PbTiO3 crystal (d33: 1500 pC N−1, TC: 135 °C, EC: 2.3 kV cm−1), the larger piezoelectricity, the higher TC and EC, and improved uniformity make Nd–PIN–PMN–PT crystals promising candidates for advanced piezoelectric applications. [ABSTRACT FROM AUTHOR]

The piezoelectric actuator is a kind of actuation device that acts through the inverse piezoelectric effect. Due to advantages of high precision, low power consumption, compact size, and flexible structure design, they have a wide range of applications in optics, robotics, microelectromechanical systems, and so on. Piezoelectric materials are the core materials for piezoelectric actuators. In this review, recent developments in high-performance piezoelectric materials (HPMs) are introduced, including relaxor ferroelectric crystals, textured ceramics, piezoelectric metamaterials, and so on. The advances of piezoelectric actuators are introduced in this review based on the developments of those piezoelectric materials, where the relationship between the figure of merits of materials and the performance of actuators is also discussed. Finally, we present outlooks and challenges for piezoelectric materials and actuators. [ABSTRACT FROM AUTHOR]

Traditional piezoelectric adaptive lenses (ALENS) are fabricated by piezoceramics with transparent liquids as the filling media. However, it is challenging to achieve high focal sensitivity and long-time robustness because of the low piezoelectricity of ceramics as well as the evaporation and leakage of the liquids. To overcome the above-mentioned issues, we design a piezoelectric lens based on a radial extension-arching mode by using polydimethylsiloxane films and Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIMNT) relaxor ferroelectric single crystals to replace the transparent liquids and Pb(Zr, Ti)O3 (PZT) ceramics, respectively. Due to the ultrahigh piezoelectric properties (d33 ∼ 1500 pC N−1 and d31 ∼ 730 pC N−1) of the PIMNT crystals and the optimized radial extension-arching structure, an ultrahigh focal sensitivity (8.5 cm V−1 and a fast response time (∼102μs) is achieved, outperforming conventional ALENS based on piezoceramic actuators (∼103 μs and ∼10−1 cm V−1) and dielectric elastomer actuators (∼105 μs and ∼10−2 cm V−1). The largest output displacement of our designed ALENS is up to 53.6 μm at 4.2 kHz under 80 Vpp, and its focus is in the range of 57.44 cm to ∞. Furthermore, its performance remains unchanged after 4 × 107 vibration cycles, indicating its long-time robustness. This work sheds light on the design of advanced adaptive optical systems, where an ultrahigh focal sensitivity and a fast response are required. [ABSTRACT FROM AUTHOR]

Relaxor‐PbTiO3 crystals exhibit excellent piezoelectric properties (d33 > 2000 pC N−1 and k33 > 90%) and thus attractes widespread attention in the past two decades. However, the inevitable segregation of components during the crystal growth results in relatively low‐performance consistency of Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) crystals, which seriously affects their practical applications. In this work, Nd3+ as A‐site substitution is introduced to improve the uniformity of electromechanical performance of PMN‐PT crystal. The results show that the crystal exhibits a high piezoelectric coefficient of 3000 pC N−1 in rhombohedral phase with a variation of 36%. The electron probe X‐ray microanalyzer indicates that the opposite separation characteristics of Nd3+ and Ti4+ lead to improved uniformity of piezoelectric performance along the crystal boule. The giant piezoelectricity in Nd‐doped PMN‐PT is attributed to the enhanced local structural heterogeneity introduced by doping Nd. Furthermore, the Nd‐doped PMN‐PT crystal shows the rhombohedral‐tetragonal phase transition temperature in the range of 74–87 °C, which indicates that Nd‐doped PMN‐PT crystal can be a promising candidate for the design of advanced piezoelectric transducers. [ABSTRACT FROM AUTHOR]

Alternating-current poling (AC-Poling) has attracted wide interests in enhancing piezoelectric performance of ferroelectric single crystals. However, the mechanism of phase transformations and domain morphology underlying AC-Poling has not been thoroughly investigated. In this work, we have systematically studied the AC-poling effect on domain structures and piezoelectric properties in the relaxor ferroelectric single crystals of 0.24Pb(In 1/2 Nb 1/2)O 3 –0.44Pb(Mg 1/3 Nb 2/3)O 3 –0.32PbTiO 3. It is shown that the piezoelectric constant (d 33) and permittivity (ε 33) are greatly enhanced via [001]-AC-poling compared to DC-poling, related to the presence of modified domain configurations as indicated previously. For [110]-oriented specimens, the piezoelectricity through AC-poling is only half as that for the DC-poled single crystals. We attribute this to the transition from the monoclinic-B phase to an orthorhombic phase under AC-poling, confirmed by synchrotron radiation X-ray diffraction and piezo-response force microscopy. The transition to the orthorhombic phase is likely a consequence of lower Gibbs energy. This study on orientation-dependent characteristics of AC-poling for PIN-PMN-PT single crystals will guide the development of AC-poling technology in applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Low driving voltage is important for miniaturization and untethered service of millirobots made of piezoelectric materials. In this research, we designed a bio-inspired bimorph-structured millirobot with a transparent relaxor ferroelectric crystal. Due to the ultrahigh piezoelectricity of the relaxor ferroelectric crystals and the optimized bimorph-based structure, the millirobot shows a maximum moving speed up to 9.22 b s−1 (body length per second) at 100 V, while the minimum driving voltage for initial movement can be as low as 3 V, which is more than two orders of magnitude smaller than that of millirobot based on dielectric elastomers. The maximum and minimum power consumptions of the millirobot are 71.6 mW and 85.9 μW, respectively. The robustness of the millirobot is reflected in its mechanical load stability carrying a 78 g mass (97.5 times of its weight) and its cryogenic tolerance. This work is believed to be beneficial to the design of various robust electromechanical devices with low driving voltage. [ABSTRACT FROM AUTHOR]

Keywords: Nd-dopants; piezoelectric transducers; piezoelectricity; relaxor ferroelectric crystals EN Nd-dopants piezoelectric transducers piezoelectricity relaxor ferroelectric crystals 1 1 1 06/21/22 20220617 NES 220617 B Piezoelectric Transducers b In article number 2201719, Fei Li, Zhuo Xu, and co-workers, by using A-site rare earth dopants, greatly enhance the piezoelectricity of PMN-PT crystals and offset the variations of properties along the crystal growth direction induced by the segregation of B-site cations. The Nd-doped PMN-PT crystals could be a promising candidate for underwater acoustic transducer applications in future. Nd-dopants, piezoelectric transducers, piezoelectricity, relaxor ferroelectric crystals. [Extracted from the article]

• Bending-bending mode piezoelectric actuator with crystal stacks are proposed and evaluated. • Ultrahigh piezoelectric coefficient d 33 of ~10,800 pC/N are achieved in actuation crystal stacks. • Due to high piezoelectricity and bending mode, max velocity is 3.28 mm/s under 130 V pp. • Minimum step resolution of 0.35 µm is demonstrated under 25 V pp driving voltage. [Display omitted] Piezoelectric actuators are important elements for compact actuations with high precision; however, driving voltage reduction is demanding for integration and minimization of precision actuations. In this work, we proposed a bending-bending mode piezoelectric actuator based on multilayered Pb(In 1/2 Nb 1/2)O 3 -Pb(Mg 1/3 Nb 2/3)O 3 -PbTiO 3 (PIN-PMN-PT) single crystals. Ultrahigh apparent piezoelectric coefficient d 33 of ~10,800 pC/N is achieved in four crystal stacks. The crystal stacks are used to fabricate bending-bending mode piezoelectric actuators to reduce driving voltage. Experimental results show that it can produce a maximum traveling velocity of 3.28 mm/s under the driving voltage of 130 V pp at 1000 Hz and minimum step resolution of 0.35 µm with 25 V pp driving voltage. Conventional piezoelectric actuators require driving voltage of ~300 V pp for similar motion velocity. This work demonstrates advantages of crystal stacks in piezoelectric actuators and potential applications in low-voltage precise actuations. [ABSTRACT FROM AUTHOR]

Alternating current (AC) electric field poling (AC-poling) has been actively studied for tailoring the domain configuration of relaxor ferroelectric crystals to further improve their piezoelectric and electro-optical properties. Understanding the change and redistribution of ferroelectric domains under AC electric field is essential for exploring the mechanism of the enhanced piezoelectricity in AC-electric-field-poled (AC-poled) crystals. Despite extensive investigations over recent years, no consensus has yet been reached on this topic. Here, we performed a three-dimensional synchrotron X-ray diffraction study on [001] C -oriented rhombohedral Pb(Mg 1/3 Nb 2/3)O 3 -PbTiO 3 (PMN-PT) ferroelectric crystals to characterize the domain structure variation during the AC-poling process. Our study clearly reveals that the AC electric field has an ability to efficiently merge the ferroelectric domains on both sides of 71o domain walls, leading to a considerable increase of domain size and thus a significant enhancement of electromechanical properties. In addition, this work indicates that, for the AC-poled [001] C -oriented rhombohedral PMN-PT crystal, the most stable state should be the lamellar domain structure with only 109o domain walls and the same volume fractions of the two types of ferroelectric domains on both sides of domain walls, which is expected to benefit the design of high-performance ferroelectric via domain or domain wall engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

The property degradation observed in thin Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) crystals is believed to relate to large domains and subsequent clamping induced by the surface boundary. In this work, the properties were investigated as function of domain size, using controlled poling. The degraded piezoelectric and dielectric properties of thin PMN–PT were found to increase significantly with decreasing domain size. Furthermore, the fine domain structure was found to be stable at 3kVcm−1 after 7.0×105 negative-pulse cycles. These properties make PMN–PT crystals suitable for high-frequency (>20MHz) ultrasound transducers. [Copyright &y& Elsevier]