Large Piezoelectric Response Research Articles

Achieving large piezoelectric response and ultrahigh electrostriction in [001] textured BiScO3‐PbTiO3 high‐temperature piezoelectric ceramics

Abstract[001] textured 0.40BiScO3‐0.60PbTiO3‐0.125 mol%Nb5+ (BS‐60PT‐0.125Nb) high‐temperature piezoelectric ceramics were synthesized using templated grain growth process. A high texture degree F001 of 99% was obtained using 2 vol% BaTiO3 (BT) templates. The piezoelectric charge constant d33 and the unipolar strain under 40 kV cm−1 at room temperature for the textured ceramics are 646 pC N−1 and 0.36%, respectively, which is over two times as those for untextured ceramics (∼243 pC N−1 and 0.17%). The electrostriction Q33 value of the textured sample remarkably increased from 0.034 m4 C−2 to 0.068 m4 C−2 under 30 kV cm−1, showing a twice higher than untextured. Compared with random ceramics, the improvement piezoelectric response of the textured ceramics is primarily attributed to the increase of the dielectric constant εr and electrostriction coefficient Q33 along [001] orientation, which is originating from the anisotropy of piezoelectricity. The BS‐60PT‐0.125Nb textured ceramics have large piezoelectric response and ultrahigh electrostriction with high temperature stability (high depolarization temperature Td of ∼360°C and high Curie temperature Tc of 421°C), showing great potential for the piezoelectric applications at high temperatures.

Structural mechanisms of large piezoelectric responses in BiFeO3-PbTiO3 based solid-solution ceramics

Achieving large piezoelectric response and high Curie temperature, simultaneously, are of great demand but have been rarely achieved in BiFeO3-PbTiO3 (BF-PT) based morphotropic phase boundary (MPB) systems. In this work, in-situ synchrotron x-ray diffraction and transmission electron microscopy were carried out in BF-PT-0.19Ba(Zr,Ti)O3 high-temperature piezoceramic, a recently reported MPB composition with high piezoelectric coefficient, to elucidate the underlying structural mechanism. A field induced irreversible transition from tetragonal (T) P4mm phase to rhombohedral (R) R3c phase is identified although R and T phases are still coexisted after poling. This induces the significantly enhanced irreversible domain switching of both R and T phases and the reversible domain switching of R phase but only a slightly enhanced reversible switching of T phase of as compared with other BF-PT-x Ba(Zr,Ti)O3 MPB compositions, leading to the significant increase of lattice strain up to ∼0.15% but only a slightly increase of strain from extrinsic domain switching due to the strong coupling between lattice strain and domain switching in both R and T phases, although the strain contribution seems to be composition independent after the field induced irreversible phase transition. The present study demonstrates a new performance enhancement mechanism to design the high-performance BF-PT based high-temperature piezoelectric ceramics in terms of the different roles of R and T phases within MPB.

Enhanced piezoelectricity in 0.7BiFeO3-0.3BaTiO3 lead-free ceramics: Distinct effect of poling engineering

BiFeO3-BaTiO3 based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature. Since the piezoelectric response of piezoelectric ceramics just appears after poling engineering, in this work, the domain evolution and microscopic piezoresponse were observed in-situ using piezoresponse force microscopy (PFM) and switching spectroscopy piezoresponse force microscopy (SS-PFM), which can effectively study the local switching characteristics of ferroelectric materials especially at the nanoscale. The new domain nucleation preferentially forms at the boundary of the relative polarization region and expands laterally with the increase of bias voltage and temperature. The maximum piezoresponse (Rs), remnant piezoresponse (Rrem), maximum displacement (Dmax) and negative displacement (Dneg) at 45 V and 120 °C reach 122, 69, 127 pm and 75 pm, respectively. Due to the distinct effect of poling engineering in full domain switching, the corresponding d33 at 50 kV/cm and 120 °C reaches a maximum of 205 pC/N, which is nearly twice as high as that at room temperature. Studying the evolution of ferroelectric domains in the poling engineering of BiFeO3-BaTiO3 ceramics provides an insight into the relationship between domain structure and piezoelectric response, which has implications for other piezoelectric ceramics as well.

First-principles study of the lattice thermal conductivity of the nitride perovskite LaWN3

Recently, ${\mathrm{LaWN}}_{3}$ nitride perovskite with polar symmetry has been synthesized and has shown a large piezoelectric response. In addition to experimentally measured piezoelectricity and theoretically predicted ferroelectricity, the thermal transport properties of ${\mathrm{LaWN}}_{3}$ remains unexplored. In this work, the phonon dispersion, lattice thermal conductivity, group velocity, phonon lifetime, phase space, and Gr\"uneisen parameters of ${\mathrm{LaWN}}_{3}$ are systematically studied using first-principles calculations. The results show that the lattice thermal conductivity of ${\mathrm{LaWN}}_{3}$ is 3.33 and 3.71 W/(mK) along the $a$ and $c$ axes at 300 K, respectively, which is comparable to some typical ferroelectric oxide perovskites such as ${\mathrm{PbTiO}}_{3}$ and ${\mathrm{BaTiO}}_{3}$. Further analyses imply that over 60% of the lattice thermal conductivity of ${\mathrm{LaWN}}_{3}$ is contributed by the optical phonons. It is found that there exists the coupling effect between the acoustic and low-lying optical phonons which limits the group velocity and the contribution to lattice thermal conductivity of acoustic phonons. Additionally, the four-phonon scattering is found to play an important role in suppressing the lattice thermal conducitivty, which is reduced by \ensuremath{\sim}50% compared to the values where only three-phonon scattering is considered.

The contribution of nonlinear behavior for large piezoelectric response in BNT-BT-based ceramics

The contribution of nonlinear behavior for large piezoelectric response in BNT-BT-based ceramics

Large Piezoelectric Response in a Metal-Free Three-Dimensional Perovskite Ferroelectric

Metal-free perovskites with light weight and eco-friendly processability have received great interest in recent years due to their superior physical features in ferroelectrics, X-ray detection, and optoelectronics. The famous metal-free perovskite ferroelectric MDABCO-NH4-I3 (MDABCO = N-methyl-N'-diazabicyclo[2.2.2]octonium) has been demonstrated to exhibit excellent ferroelectricity comparable to that of inorganic ceramic ferroelectric BaTiO3, such as large spontaneous polarization and high Curie temperature (Ye et al. Science 2018, 361, 151). However, piezoelectricity as a vitally important index is far from enough in the metal-free perovskite family. Here, we report the discovery of large piezoelectric response in a new metal-free three-dimensional perovskite ferroelectric NDABCO-NH4-Br3 (NDABCO = N-amino-N'-diazabicyclo[2.2.2]octonium) by replacing the methyl group of MDABCO with the amino group. Besides the evident ferroelectricity, strikingly, NDABCO-NH4-Br3 shows a large d33 of 63 pC/N more than 4 times that of MDABCO-NH4-I3 (14 pC/N). The d33 value is also strongly supported by the computational study. To the best of our knowledge, such a large d33 value ranks the highest among the documented organic ferroelectric crystals to date and represents a major breakthrough in metal-free perovskite ferroelectrics. Combined with decent mechanical properties, NDABCO-NH4-Br3 is expected to be a competitive candidate for medical, biomechanical, wearable, and body-compatible ferroelectric devices.

Electric field-induced irreversible phase transformations in Pb(Zr, Ti)O3-based piezoceramics

La-modified Pb(Zr,Ti)O3 (PLZT) (d33 ∼ 650 pC/N) and unmodified Pb(Zr1-x, Tix)O3 in the composition range (0.35 = x ≤ 0.51) were electrically poled through a novel powder poling technique. The mechanisms of large piezoelectric response in morphotropic phase boundary (MPB) and non-MPB-based compositions were discussed. Structural analysis suggests MPB-based compositions undergo irreversible structural phase transformation and lattice distortion after poling, and non-MPB undergo irreversible structural phase transformation. In the framework of theories, it has been argued that the MPB compositions satisfy the polarization rotation cum structural distortion phenomenon and non-MPB-based compositions follow the polarization rotation model.

Enhanced piezoelectric response of Aurivillius ferroelectrics by constructing a novel solid solution and combining traditional chemical substitution

With the increasing demand for high-temperature piezoelectric ceramics, excellent piezoelectricity and high Curie temperature are required simultaneously. Herein, combining the advantages of constructing new-type solid solutions and traditional A-site doping strategy, Aurivillius ferroelectrics (Na0.5Bi0.5)0.5−x/2(Li0.5Ce0.5)x/2Bi2.5Ti0.5Nb1.5O9 (NBTN-LC100x, x = 0–0.16) were designed to achieve the large piezoelectric response and high Curie temperature simultaneously. The existence of a pseudo-tetragonal phase boundary together with the reduction of domain size produces a large piezoelectric coefficient (d33 ∼ 24.6 pC/N) with a fairly high TC (∼825 °C). Moreover, pseudo-tetragonal distortion might be responsible for the excellent thermal stability of d33 against thermal depolarization temperature (Td). For NBTN-LC12, high-temperature electric resistivity is still above 1 × 105 Ω cm at 600 °C. The improved comprehensive properties of NBTN-LC100x ceramics demonstrate that the construction of a novel Aurivillius ferroelectrics is a promising way to explore high-temperature sensor materials.

Vector piezoelectric response and ferroelectric domain formation in Hf0.5Zr0.5O2 films

The evolution of the vector piezoelectric response of Hf0.5Zr0.5O2 films on SrTiO3 substrates with different orientations shows the large and anisotropic in-plane piezoelectric response in films grown on SrTiO3(110).

Two-dimensional Janus Si dichalcogenides: a first-principles study.

Strong structural asymmetry is actively explored in two-dimensional (2D) materials, because it can give rise to many interesting physical properties. Motivated by the recent synthesis of monolayer Si2Te2, we explored a family of 2D materials, named Janus Si dichalcogenides (JSD), which parallel the Janus transition metal dichalcogenides and exhibit even stronger inversion asymmetry. Using first-principles calculations, we show that their strong structural asymmetry leads to a pronounced intrinsic polar field, sizable spin splitting, and large piezoelectric response. The spin splitting involves an out-of-plane spin component, which is beyond the linear Rashba model. The piezoelectric tensor has a large value in both in-plane d11 coefficient and out-of-plane d31 coefficient, making monolayer JSDs distinct among existing 2D piezoelectric materials. In addition, we find interesting strain-induced phase transitions in these materials. Particularly, there are multiple valleys that compete for the conduction band minimum, which will lead to notable changes in the optical and transport properties under strain. Our work reveals a new family of Si based 2D materials, which could find promising applications in spintronic and piezoelectric devices.

Charge transport characteristic and charge stability enhancement mechanism of polyimide aerogel as an ultralight weight electret

In this study, polyimide aerogel (PIA) is applied as an ultralight-weight and thermally stable electret material, meanwhile its charge transport characteristic and charge stability enhancement mechanism are investigated. It is found that PIA can exhibit excellent electret properties at 120 °C after corona charging at room temperature, and its charge stability acquires further promotion after charging at elevated temperatures or heat treatment, which far exceeds conventional polyimide-based electrets. Further research indicates that the outstanding charge retention characteristics of PIA originate from the enhanced local defect density, fast retrapping effect, weakened internal electric field by dipole polarization, and prolonged conduction path, which are inextricably linked to its porous structure. In addition, the high gas breakdown strength in the pores of PIA effectively limits the breakdown induced conductivity, thereby ensuring high space charge density and large piezoelectric response of PIA electrets. Considering the extremely low density and inherently excellent properties of polyimide substances, PIA may have promising prospects as an electret in the lightweight sensing and energy conversion devices at elevated temperatures.

Large effective piezoelectric response from the spontaneously polarized surface layer in P(VDF-TrFE) arch films

In this work, we show that a [Formula: see text]150 pC/N can be obtained in nonpoled poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) copolymer films with an arch structure. The copolymer films, which are often thought to be homogeneous, are in fact inhomogeneous in microstructure and physical properties after film fabrication. Although a large proportion of the copolymer film is nonpolar, as expected in a nonpoled ferroelectric film, the surface regions of the film are spontaneously polarized. We propose that inhomogeneous stress in the surface regions, which is either from the constraint of the substrate or skin layer effect formed during the film fabrication, generates a flexoelectric response and orients the spontaneous polarization of the ferroelectric film. As a result of the polar surface regions, the nonpoled films exhibit a piezoelectric response. The piezoelectric response is further amplified by the special arch structure of the films, leading to the observed large effective piezoelectric response. This study not only discovers the polar surface effect in ferroelectric polymer films, but also proposes an approach to design polymer materials with a strong piezoelectric response.

Enhanced electromechanical properties in MnCO3‐modified Pb(Ni,Nb)O3–PbZrO3–PbTiO3 ceramics via defect and domain engineering

AbstractThe development of piezoelectric ceramics with both large piezoelectric responses and mechanical quality factor is still a key challenge for practical applications for high‐power piezoelectric devices. Here we report the strategy to utilize the synergistic contribution of engineered defect and domain structure, in which an excellent piezoelectric coefficient d33 of 655 pC N−1 and mechanical quality factor Qm of 371 are simultaneously achieved in MnCO3‐modified Pb(Ni,Nb)O3–PbZrO3–PbTiO3 (Mn‐PNN–PZ–PT) ceramics. Meanwhile, the depolarization temperature (Td) and the temperature corresponding to the εr,max (Tm) are enhanced relative to the pure counterpart. After annealing at 90°C, the sample with x = 0.3 shows the retained d33 value of 610 pC N−1, about 2.6 times larger than that with x = 0 counterpart, demonstrating a wider operating temperature range. These enhanced electromechanical properties originate from the internal bias field introduced by the defect dipoles and . It is verified that xMn‐PNN–PZ–PT ceramics have superior potential for high‐power application, meanwhile, paves a significant step toward enhancing the thermal stability of high‐temperature piezoceramics.

Inch-Size Molecular Ferroelectric Crystal with a Large Electromechanical Coupling Factor on Par with Barium Titanate.

Molecular ferroelectrics with large piezoelectric responses have long been sought for their advantages of light weight, mechanical flexibility, and easy preparation, in contrast to the widely used inorganic counterparts. Representatively, a molecular ferroelectric crystal [Me3NCH2Cl]CdCl3 (TMCM-CdCl3) has been found to show a large piezoelectric coefficient d33 of 220 pC/N exceeding that of BaTiO3 (You et al. Science2017, 357, 306-309). However, although the d33 of molecular ferroelectrics has achieved great progress, their electromechanical coupling factor k33, which is essential for various piezoelectric applications, including ultrasonic transducers and actuators, was rarely explored and is far below the level of inorganic ferroelectrics. The major reason for this situation is the great challenge of growing large-size crystals which is a key limiting factor for measuring k33. Here, we grew inch-size crystals of organic-inorganic perovskite ferroelectric TMCM-CdCl3 with a high d33 (383 pC/N) for investigating its piezoelectric responses including the k33 (0.483) by the resonance method. Such high k33 (0.483) is much larger than those of other molecular ferroelectrics and competitive with that of BaTiO3 (0.5). In addition, TMCM-CdCl3 has a low elastic modulus of 13.03 GPa, an order of magnitude lower than that of BaTiO3. This finding sheds light on the exploration of large electromechanical coupling factors in molecular ferroelectrics for potential applications in flexible and portable piezoelectric devices.

Misfit-Strain Phase Diagram, Electromechanical and Electrocaloric Responses in Epitaxial PIN-PMN-PT Thin Films.

xPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 (PIN-PMN-PT) bulks possess excellent electromechanical coupling and dielectric properties, but the corresponding epitaxial PIN-PMN-PT thin films have not yet been explored. This paper adopts a nonlinear thermodynamics analysis to investigate the influences of misfit strains on the phase structures, electromechanical properties, and electrocaloric responses in epitaxial PIN-PMN-PT thin films. The misfit strain-temperature phase diagram was constructed. The results reveal that the PIN-PMN-PT thin films may exist in tetragonal c-, orthorhombic aa-, monoclinic M-, and paraelectric PE phases. It is also found that the c-M and aa-PE phase boundaries exhibit a superior dielectric constant ε11 which reached 1.979 × 106 with um = -0.494%, as well as the c-M phase boundary showing a large piezoelectric response d15 which reached 1.64 × 105 pm/V. In comparison, the c-PE and M-aa phase boundaries exhibit a superior dielectric constant ε33 over 1 × 105 around um = 0.316% and the piezoelectric response d33 reached 7235 pm/V. The large electrocaloric responses appear near the paraelectric- ferroelectric phase boundary. These insights offer a guidance for experiments in epitaxial PIN-PMN-PT thin films.

Enhancing depolarization temperature and thermal stability of KNN-based piezoelectric ceramics through Li substitution and Al2O3 doping

Obtaining both large piezoelectric responses and broad service temperature range of ferroelectric ceramics is a key challenge for practical applications due to the so-called piezoelectric coefficient (d33)-Curie temperature (TC) trade-off. Here we report the strategy of employing Li substitution and Al2O3 doping in order to enhance the depolarization temperature (Td) and thermal stability of (K,Na)NbO3 (KNN)-based lead-free piezoelectric ceramics. All KNN-based ceramics are fabricated using conventional solid-state reaction techniques. Optimal comprehensive properties of d33 = 205 pC/N, kp = 46.5%, ε33T/ε0 = 998, tan δ = 0.047, Td = 470 °C are obtained with Li substitution of 6.5 mol%. Furthermore, doping 0.2 mol% Al2O3 improves the thermal stability in the whole working temperature range of 25 – 470 °C with a d33 decrement less than 10%, keeping the relatively high d33 of 200 pC/N even at high temperature (400 – 470 °C). The Al2O3 doping shows a further effect of inhibiting grain growth, which significantly reduces the grain size of ceramics. The results obtained in this work pave the way for the practical application of KNN-based ceramics at high temperature, such as aerospace sensors, oilfield logging, engine monitoring and injection nozzles in automobiles.

Morphotropic phase boundary in pure perovskite lead titanate at room temperature

For many decades, great efforts have been devoted to pursue a large piezoelectric response by an intelligent design of morphotropic phase boundaries (MPB) in solid solutions, where tetragonal (T) and rhombohedral (R) structures coexist. For example, classical PbZrxTi1-xO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals demonstrate a giant piezoelectric response near MPB. However, as the end member of these solids, perovskite-structured PbTiO3 always adopts the T phase at room temperature. Here, we report a pathway to create room temperature MPB in a single-phase PbTiO3. The uniaxial stress along the c-axis drives a T-R phase transition bridged by a monoclinic (M) phase, which facilitates a polarization rotation in the monodomain PbTiO3. Meanwhile, we demonstrate that the coexistence of T and R phases at room temperature can be achieved via an extremely mismatched heterointerface system. The uniaxial pressure is proved as an efficient way to break the inherent symmetry and able to substantially tailor the phase transition temperature Tc. These findings provide new insights into MPB, offering the opportunity to explore the giant piezoelectric response in single-phase materials.

An Effective Strategy of Introducing Chirality to Achieve Multifunctionality in Rare‐Earth Double Perovskite Ferroelectrics (Small Methods 9/2022)

Inside Front Cover In article number 2200421, Song, You, Zhang, and co-workers found that the introduction of chirality is an efficient strategy for the targeted construction of multifunctionality, which simultaneously increased the possibility of obtaining multiaxial ferroelectricity and ferroelasticity, and effectively realized a large piezoelectric response. Moreover, chirality-induced ferroelasticity would also achieve excellent magnetic or optical response driven by pressure.

Homogenization of electrets with ellipsoidal microstructure and pathways for designing piezoelectricity in soft materials

True piezoelectricity in soft materials is rare if not virtually non-existent. This impedes applications where both large deformation and a strong electromechanical coupling are desirable e.g. soft robotics, biomedical sensors and actuators, a class of energy harvesting devices among others. The widely used soft dielectric elastomers rely on the electrostatic Maxwell stress effect for electromechanical coupling — a one-way quadratic effect that requires extremely large voltage for actuation and does not allow for the facile conversion of mechanical deformation into electricity. Prior research has shown that embedding (and stabilizing) immobile charges or dipoles in soft matter i.e. creating so-called electrets, can lead to an emergent piezoelectric effect. In this work, using a recently developed homogenization theory for soft electret materials, we derive closed-form expressions to design soft apparently piezoelectric materials with an ellipsoidal microstructure. Specifically, we determine both effective longitudinal (d33) and transverse (d31) piezoelectric coefficients of the material and study the impact of the material properties on these two coefficients. Conventional electrets exhibit a rather weak d31, which is quite disadvantageous for applications where flexure is important (e.g. energy harvesting). Either an elastic, or a dielectric contrast is essential for the emergence of piezoelectricity in electrets and, depending on the microstructural details, these two effects can either strengthen or diminish the other. Our results indicate that the microstructure and material properties which lead to an optimum d33 effect are different from the conditions underlying the optimal d31 response. The maximum d31 effect is observed in electrets where the inclusions are mechanically harder but dielectrically softer than the matrix material. Finally, we find that a significantly large d33 piezoelectric response is possible for spheroid inclusion microstructures with large aspect ratios.

Predicted ferromagnetic monolayer CrSCl with large vertical piezoelectric response: A first-principles study

For two-dimensional (2D) materials, piezoelectric ferromagnetism with large out-of-plane piezoresponse is highly desirable for multifunctional ultrathin piezoelectric device application. Here, we predict that Janus monolayer CrSCl is an out-of-plane ferromagnetic semiconductor with large vertical piezoelectric response and high Curie temperature. The predicted out-of-plane piezoelectric strain coefficient d31 is −1.58 pm/V, which is higher than that of most 2D materials (compare absolute values of d31). The large out-of-plane piezoelectricity is robust against electronic correlation and biaxial strain, confirming reliability of large d31. The calculated results show that tensile strain is conducive to high Curie temperature, large magnetic anisotropy energy, and large d31. Finally, by comparing d31 of CrYX (Y = S; X = Cl, Br, I) and CrYX (Y = O; X = F, Cl, Br), we conclude that the size of d31 is positively related to electronegativity difference of X and Y atoms. Such findings can provide valuable guidelines for designing 2D piezoelectric materials with large vertical piezoelectric response.