High-performance Piezoelectrics Research Articles

Mass Production Technology for High-performance Piezoelectric Thin Films for MEMS Devices

Mass Production Technology for High-performance Piezoelectric Thin Films for MEMS Devices

Toward Ecofriendly Piezoelectric Ceramics-Reduction of Energy and Environmental Footprint from Conceptualization to Deployment.

Piezoelectric materials are widely used in electromechanical coupling components including actuators, kinetic sensors, and transducers, as well as in kinetic energy harvesters that convert mechanical energy into electricity and thus can power wireless sensing networks and the Internet of Things (IoT). Because the number of deployed energy harvesting powered systems is projected to explode, the supply of piezoelectric energy harvesters is also expected to be boosted. However, despite being able to produce green electricity from the ambient environment, high-performance piezoelectrics (i.e., piezoelectric ceramics) are energy intensive in research and manufacturing. For instance, the design of new piezoceramics relies on experimental trials, which need high process temperatures and thus cause high consumption and waste of energy. Also, the dominant element in high-performance piezoceramics is hazardous Pb, but substituting Pb with other nonhazardous elements may lead to a compromise of performance, extending the energy payback time and imposing a question of trade-offs between energy and environmental benefits. Meanwhile, piezoceramics are not well recycled, raising even more issues in terms of energy saving and environmental protection. This paper discusses these issues and then proposes solutions and provides perspectives to the future development of different aspects of piezoceramic research and industry.

New High-Performance Piezoelectric: Ferroelectric Carbon-Boron Clathrate.

High-performance piezoelectrics have been extensively reported with a typical perovskite structure, in which a huge breakthrough in piezoelectric constants is found to be more and more difficult. Hence, the development of materials beyond perovskite is a potential means of achieving lead-free and high piezoelectricity in next-generation piezoelectrics. Here, we demonstrate the possibility of developing high piezoelectricity in the nonperovskite carbon-boron clathrate with the composition of ScB_{3}C_{3} using first-principles calculations. The robust and highly symmetric B-C cage with mobilizable Sc atom constructs a flat potential valley to connect the ferroelectric orthorhombic and rhombohedral structures, which allows an easy, continuous, and strong polarization rotation. By manipulating the cell parameter b, the potential energy surface can be further flattened to produce an extra-high shear piezoelectric constant d_{15} of 9424 pC/N. Our calculations also confirm the effectiveness of the partial chemical replacement of Sc by Y to form a morphotropic phase boundary in the clathrate. The significance of large polarization and high symmetric polyhedron structure is demonstrated for realizing strong polarization rotation, offering the universal physical principles to aid the search for new high-performance piezoelectrics. This work takes ScB_{3}C_{3} as an example to exhibit the great potential for realizing high piezoelectricity in clathrate structure, which opens the door to developing next-generation lead-free piezoelectric applications.

Giant electric field–induced strain in lead-free piezoceramics

Piezoelectric actuators are indispensable over a wide range of industries for their fast response and precise displacement. Most commercial piezoelectric actuators contain lead, posing environmental challenges. We show that a giant strain (1.05%) and a large-signal piezoelectric strain coefficient (2100 picometer/volt) are achieved in strontium (Sr)-doped (K,Na)NbO3 lead-free piezoceramics, being synthesized by the conventional solid-state reaction method without any post treatment. The underlying mechanism responsible for the ultrahigh electrostrain is the interaction between defect dipoles and domain switching. The fatigue resistance, thermal stability, and strain value (0.25%) at 20 kilovolt/centimeter are comparable with or better than those of commercial Pb(Zr,Ti)O3-based ceramics, showing great potential for practical applications. This material may provide a lead-free alternative with a simple composition for piezoelectric actuators and a paradigm for the design of high-performance piezoelectrics.

Bond engineering of molecular ferroelectrics renders soft and high-performance piezoelectric energy harvesting materials

Piezoelectric materials convert mechanical stress to electrical energy and thus are widely used in energy harvesting and wearable devices. However, in the piezoelectric family, there are two pairs of properties that improving one of them will generally compromises the other, which limits their applications. The first pair is piezoelectric strain and voltage constant, and the second is piezoelectric performance and mechanical softness. Here, we report a molecular bond weakening strategy to mitigate these issues in organic-inorganic hybrid piezoelectrics. By introduction of large-size halide elements, the metal-halide bonds can be effectively weakened, leading to a softening effect on bond strength and reduction in polarization switching barrier. The obtained solid solution C6H5N(CH3)3CdBr2Cl0.75I0.25 exhibits excellent piezoelectric constants (d33 = 367 pm/V, g33 = 3595 × 10−3 Vm/N), energy harvesting property (power density is 11 W/m2), and superior mechanical softness (0.8 GPa), promising this hybrid as high-performance soft piezoelectrics.

Getting the Lead Out: Biomolecular Crystals as Low-Cost, High-Performance Piezoelectric Components.

Getting the Lead Out: Biomolecular Crystals as Low-Cost, High-Performance Piezoelectric Components.

Flexible polarization configuration in high-entropy piezoelectrics with high performance

Polarization configuration engineering by compositional and structural tuning in piezoelectrics holds great promise for high piezoelectricity that benefits wide electromechanical applications. Here, a novel flexible polarization configuration is achieved in high-entropy Pb-based perovskites, which contributes to superior piezoelectricity of d33 ∼1200 pC/N. Emergent characteristics and behaviors of such a flexible polarization configuration are thoroughly investigated by the combination of atomic-scale scanning transmission electron microscopy, in-situ high-energy synchrotron X-ray diffraction, and first-principles calculations. The multiple interactions among the A and B-site atoms, originating from the increase of the species of B-site elements as well as the enhanced entropy of the system, weaken the long-range polarization order, enhance the flexibility of the polarization under the external field, and eventually result in the high piezoelectric performance. This work demonstrates that polarization configuration engineering through the high-entropy method would be an effective strategy for obtaining outstanding piezoelectric properties, which provides new opportunities for the design and discovery of high-performance piezoelectrics.

High Piezoelectric Performance in Pb(Ni1/3Nb2/3)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 Ternary System Featuring Small Structural Distortion and Heterogeneous Domain Configuration.

Ternary/polynary perovskite solid solutions based on binary systems are well-known for their high piezoelectric performance. In this work, a series of Pb(Ni1/3Nb2/3)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 compositions with the particularly high piezoelectric coefficient of d33* > 1000 pm/V and d33 > 700 pC/N have been developed. The optimal performance was achieved in the 0.52PNN-0.14PSN-0.34PT composition (d33* = 1120 pm/V, d33 = 804 pC/N, and Tm = 109 °C). The high piezoelectric performance of this system is reported and is superior to those of most lead-based ternary/polynary ceramics. By a combination of in situ high-energy synchrotron diffraction with transmission electron microscopy (TEM), the origin of the high piezoelectric response has been unambiguously revealed. Upon application of an external electric field, synchrotron diffraction profiles show no splitting but prominent shifting, indicating that the large intrinsic lattice strain arising from the reduced crystal anisotropy and facilitated polarization variation is associated with the high piezoelectric response. Furthermore, microscopic studies by TEM highlight a heterogeneous ferroelectric domain configuration generated by a small local structural distortion, which is also beneficial for the high piezoelectric performance in the proposed ternary piezoelectric systems. The design process of ternary perovskite solid solutions with a wide morphotropic phase boundary region and small structural distortion may be enlightening for the exploration of other high-performance polynary piezoelectrics.

Microribbon Structured Polyvinylidene Fluoride with High-Performance Piezoelectricity for Sensing Application

Rapid development in artificial intelligence has increased the demand for portable and sustainable power sources. As one of the most important self-powered sensors, piezoelectric generator (PEG) ha...

Towards high-performance linear piezoelectrics: Enhancing the piezoelectric response of zinc oxide thin films through epitaxial growth on flexible substrates

Ferroelectrics are popular for sensors, actuators and transducers. However, the energy barrier for reversing the polarization leads to extra energy losses, while the hysteresis causes phase-lags and non-linearities between input and output signals. The high piezoelectric constants of ferroelectrics dictate the figure-of-merit of piezoelectric devices. Enhancing the piezoelectric constant of linear-piezoelectrics potentially leads to next-generation piezoelectric devices free from issues associated with ferroelectrics. By epitaxial growth of undoped ZnO films on flexible Hastelloy substrates, we demonstrated an ~85% improvement in the piezoelectric constant, and more importantly maintained the linearity of the piezoelectric response. Strong out-of-plane and in-plane crystallographic alignments are detected in the epitaxial sample, yet modeling of the effective thin-film piezoelectric constant shows only a limited contribution of the optimized textures. The improvement in the piezoelectric response is ascribed mostly to the in-plane epitaxial strain resulted from the lattice mismatch of ZnO to the substrate. The epitaxial ZnO film on Hastelloy promisingly offer high-precision positioners with nano-/pico-meter resolutions. Enhancing the piezoelectric constant by strain engineering potentially removes the barrier for applications of linear-piezoelectrics and enriches the piezoelectric research community.

Phase-field simulation of magnetic microstructure and domain switching in (Tb0.27Dy0.73)Fe2 single crystal

The morphotropic phase boundary (MPB), separating two ferroic phases with rhombohedral and tetragonal crystal symmetries, has been utilized extensively in ferroelectrics because it can lead to high-performance piezoelectricity. Recently, a parallel ferromagnetic MPB was experimentally reported and was suggested that the optimal point for magneto-mechanical applications might lies on the rhombohedral side. However, the insight of the domain structures and switching mechanism near ferromagnetic MPB is still unclear. In this work, phase-field micromagnetic microelastic modeling was employed to simulate the domain formation and magnetization switching of (Tb0.27Dy0.73)Fe2, whose composition is around the rhombohedral side of ferromagnetic MPB. The results show that four kinds of domains of the rhombohedral phase automatically form twins of {110} or {100} boundaries with 71° and 109° domain walls after a process of nucleation and growth. The rhombohedral domain evolution and phase volume fraction under the external field of 120 kA/m along different directions are investigated. In ferromagnetics subject to an alternating magnetic field, domain magnetization switches to cause a magnetization hysteresis loop and an associated butterfly magnetostriction loop with the alternating magnetic field.

Role of tetragonal distortion on domain switching and lattice strain of piezoelectrics by in-situ synchrotron diffraction

The tetragonal phase is an indispensable component that plays an important role in forming the morphotropic phase boundary. Herein, the piezoelectric behaviors are systematically investigated in various Pb/Bi-based tetragonal piezoelectric systems as a function of tetragonal distortion using in-situ high-energy synchrotron diffraction. It is found that the tetragonal distortion has a significant influence on piezoelectric properties through constraining the domain switching. Specifically, a critical value of (c/a-1) ≈ 1.5 % is identified, below which the domain switching is significantly activated. The correlation between piezoelectric performance and the cooperative contribution of tetragonal distortion and domain switching has been established: Reducing tetragonal distortion and activating domain switching can enhance the piezoelectric coefficient. Furthermore, an approximate linear coupling between domain switching and lattice strain is confirmed in tetragonal piezoelectric systems. Insights from this work would facilitate the design of high-performance piezoelectrics, by controlling tetragonal distortion and domain switching.

Achieving high piezoelectric performances with enhanced domain-wall contributions in -textured Sm-modified PMN-29PT ceramics

1% Sm substituted PMN-29PT ([Sm0.01Pb0.985][(Mg1/3Nb2/3)0.71Ti0.29]O3) textured ceramics with a Lotgering factor of up to 80 % were successfully prepared. The dielectric, ferroelectric and piezoelectric properties have been investigated in detail for both textured and non-textured ceramics. The heterogeneous templates are found to be critical for the change in relaxor behaviors, leading to the reduced Tf, Tm, εmax and Pr in textured ceramics. The textured ceramics show an enhanced d33 of 810 pC/N, about 1.6 times greater than their randomly oriented ceramic counterparts. The domain structures and their responses to applied electric fields have been studied using piezoresponse force microscopy, signifying the enhanced extrinsic contributions by the increased domain wall densities and dynamics. The improved dielectric and piezoelectric properties are discussed and explained from the view point of extrinsic contributions in textured ceramics. The results demonstrate that the textured Sm-PMN-PT piezoelectric ceramics could be promising high performance piezoelectrics with low cost.

Relaxor behavior of potassium sodium niobate ceramics by domain evolution

Relaxor behavior is proved to be responsible for high piezoelectricity in piezoelectric materials due to the promoted polarization rotation, and an ultrahigh piezoelectricity can be also induced in potassium sodium niobate [(K,Na)NbO3, KNN]-based ceramics by dielectric relaxation at the multiphase coexistence region. However, it is still absent of the association study between domain evolution and relaxor behavior created by nanoscale multiphase coexistence. Herein, the frequency-dependent domain response, dwell-time dependence of domain radius and voltage-dependent domain switching are characterized in KNN-based ceramics with relaxor R–T phase boundary. These novel domain evolutions further illustrate the contribution of relaxor behavior on high piezoelectricity, yielding to easy polarization rotation based on low energy barrier of polar nanoregions merging into long-range ordering states. And an improved temperature stability is observed at 30−60 °C for relaxor R–T due to the unusual domain evolution. This study affords a new perspective in the mechanism of high-performance lead-free piezoelectrics.

Grain-Oriented Ferroelectric Ceramics with Single-Crystal-like Piezoelectric Properties and Low Texture Temperature

High-performance piezoelectrics are pivotal to various electronic applications including multilayer actuators, sensors, and energy harvesters. Despite the presence of high Lotgering factor F001, two key limitations to today's relaxor-PbTiO3 textured ceramics are low piezoelectric properties relative to single crystals and high texture temperature. In this work, Pb(Yb1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PYN-PMN-PT) textured ceramics with F001 ∼ 99% were synthesized at only 975 °C through liquid-phase-assisted templated grain growth, where of particular significance is that single-crystal properties, i.e., very large electrostrain Smax/Emax ∼ 1830 pm V-1, giant piezoelectric figure of merit d33 × g33 ∼ 61.3 × 10-12 m2 N-1, high electromechanical coupling k33 ∼ 0.90, and Curie temperature Tc ∼ 205 °C, were simultaneously achieved. Especially, the Smax/Emax and d33 × g33 values correspond to ∼180% enhancement as compared to the regularly 1200 °C-textured ceramics with F001 ∼ 96%, representing the highest values ever reported on piezoceramics. Phase-field simulation revealed that grain misorientation has a stronger influence on piezoelectricity than texture fraction. The ultrahigh piezoelectric response achieved here is mainly attributed to effective control of grain orientation features and domain miniaturization. This work provides important guidelines for developing novel ceramics with significantly enhanced functional properties and low synthesis temperature in the future and can also greatly expand application fields of piezoceramics to high-performance, miniaturized electronic devices with multilayer structures.

Structure and good piezoelectric performance in the complex system of Pb[(Zn,Ni)Nb]O3–Pb[(In,Yb)Nb]O3–Pb(Zr,Hf,Ti)O3

High-performance piezoelectrics are always demanded for the high-end application. Herein, a complex piezoelectric system of 0.49Pb(Zn1/2Ni1/2)1/3Nb2/3O3–xPb(In1/2Yb1/2)1/2Nb1/2O3–(0.51 − x)Pb(Zr1/2Hf1/2)0.1Ti0.9O3 (0.16 ≤ x ≤ 0.23) was fabricated through the solid-state method. The structure, ferroelectric, piezoelectric, and dielectric properties were investigated. The optimum piezoelectric coefficient d33 of 761 pC/N, high Curie temperature of 169 °C, dielectric permittivity (ɛr) of 4557, and electromechanical coupling coefficient (kp) of 63% were found at the morphotropic phase boundary composition of x = 0.19, which are superior to other complex piezoelectric materials. In particular, a significant large-signal d33∗ of 913 pm/V and low strain hysteresis (6%) was obtained in the temperature range of 20–170 °C. Temperature-dependent x-ray diffraction (XRD) has demonstrated that good temperature stability is put down to the structure stability. The agreement between the calculated lattice strain from in situ high-energy synchrotron XRD data and the macroscopic measurements suggests that the large lattice strain has a dominant contribution to the high piezoelectric response. The high piezoelectric performance and good temperature stability makes it potential for application.

Unexpectedly high piezoelectric response in Sm-doped PZT ceramics beyond the morphotropic phase boundary region

Abstract Compositional design by multiphase coexistence is regarded as a guiding rule for material design to develop high-performance piezoelectric materials. An open question is whether a certain PZT composition outside of the morphotropic phase boundary (MPB) region can obtain high piezoelectric response like that close to MPB region. Here, a non-MPB composition, rhombohedral Pb(Zr0.54Ti0.46)O3 was selected as the parent material. The optimized electrical properties were obtained by Sm doping with a large piezoelectric coefficient d33 of 590 pC/N, a high planar electromechanical coupling factors kp of 57.1%, a large piezoelectric strain S of 0.31% (d33∗ = 632 pm/V), and a promising Curie temperature of 335 °C, compared to the commercial PZTs. The enhancement of piezoelectric response can be ascribed to the donor characteristics by Sm replacement, which contribute to polarization orientation of ferroelectric dipoles. This work broadens the domain of high-performance piezoelectrics by developing novel solid solutions beyond the MPB framework.

Transparent ferroelectric crystals with ultrahigh piezoelectricity.

Transparent piezoelectrics are highly desirable for numerous hybrid ultrasound-optical devices ranging from photoacoustic imaging transducers to transparent actuators for haptic applications1-7. However, it is challenging to achieve high piezoelectricity and perfect transparency simultaneously because most high-performance piezoelectrics are ferroelectrics that contain high-density light-scattering domain walls. Here, through a combination of phase-field simulations and experiments, we demonstrate a relatively simple method of using an alternating-current electric field to engineer the domain structures of originally opaque rhombohedral Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals to simultaneously generate near-perfect transparency, an ultrahigh piezoelectric coefficient d33 (greater than 2,100picocoulombs per newton), an excellent electromechanical coupling factor k33 (about 94 per cent) and a large electro-optical coefficient γ33 (approximately 220picometres per volt), which is far beyond the performance of the commonly used transparent ferroelectric crystal LiNbO3. We find that increasing the domain size leads to a higher d33 value for the [001]-oriented rhombohedral PMN-PT crystals, challenging the conventional wisdom that decreasing the domain size always results in higher piezoelectricity8-10. This work presents a paradigm for achieving high transparency and piezoelectricity by ferroelectricdomain engineering, and we expect the transparent ferroelectric crystals reported here to provide a route to a wide range of hybrid device applications, such as medical imaging, self-energy-harvesting touch screens and invisible robotic devices.

Practical high-performance lead-free piezoelectrics: structural flexibility beyond utilizing multiphase coexistence.

Due to growing concern for the environment and human health, searching for high-performance lead-free piezoceramics has been a hot topic of scientific and industrial research. Despite the significant progress achieved toward enhancing piezoelectricity, further efforts should be devoted to the synergistic improvement of piezoelectricity and its thermal stability. This study provides new insight into these topics. A new KNN-based lead-free ceramic material is presented, which features a large piezoelectric coefficient (d33) exceeding 500 pC/N and a high Curie temperature (Tc) of ∼200°C. The superior piezoelectric response strongly relies on the increased composition-induced structural flexibility due to lattice softening and decreased unit cell distortion. In contrast to piezoelectricity anomalies induced via polymorphic transition, this piezoelectricity enhancement is effective within a broad temperature range rather than a specific small range. In particular, a hierarchical domain architecture composed of nano-sized domains along the submicron domains was detected in this material system, which further contributes to the high piezoelectricity.

Understanding, Predicting, and Designing Ferroelectric Domain Structures and Switching Guided by the Phase-Field Method

Understanding mesoscale ferroelectric domain structures and their switching behavior under external fields is critical to applications of ferroelectrics. The phase-field method has been established as a powerful tool for probing, predicting, and designing the formation of domain structures under different electromechanical boundary conditions and their switching behavior under electric and/or mechanical stimuli. Here we review the basic framework of the phase-field model of ferroelectrics and its applications to simulating domain formation in bulk crystals, thin films, superlattices, and nanostructured ferroelectrics and to understanding macroscopic and local domain switching under electrical and/or mechanical fields. We discuss the possibility of utilizing the structure-property relationship learned from phase-field simulations to design high-performance relaxor piezoelectrics and electrically tunable thermal conductivity. The review ends with a summary of and an outlook on the potential new applications of the phase-field method of ferroelectrics.