Large Piezoelectric Response Research Articles

Strain-Induced Tunable Enhancement of Piezoelectricity in a Novel Molecular Multiferroic Material.

Multiferroics are appealing because of application potentials in data storage devices, sensors, transducers, and energy harvesters. Molecular multiferroics emerge as a promising alternative to inorganic multiferroics due to flexibility, light weight, low toxicity, solution processing, structural diversity, and chemical tunability. While researches have predominantly focused on perovskite structures, studies on molecular ionic multiferroics remain relatively limited. It is urgent to creatively build a novel platform for studying and developing the coupling and interaction between the stress, electricity, and magnetism. Knowing this, the work focuses on a novel organic-inorganic hybrid multiferroic N-ethyl-N-(fluoromethyl)-N-methylethylammonium tetrabromoferrate (III) showing coexisting magnetic and electric orderings. It undergoes antiferromagnetic, ferroelectric, and ferroelastic transitions. Notably, under a strain of 2.0%, the piezoelectric response increases tenfold, and the coercive field of ferroelectric polarization is reduced by half. The strain-induced enhancement of piezoelectricity is rarely reported in molecular multiferroics. Density functional theory is employed to predict that the mechanism of the large piezoelectric response under strain engineering is related to the cation rotation and phase switching between the stable phase and an energetically competitive metastable phase. This study creates a new paradigm to develop molecular multiferroics and future microelectronic devices for energy conversion.

Exploring Aqueous Solution-Processed Pseudohalide Rare-Earth Double Perovskite Ferroelectrics toward X-Ray Detection with High Sensitivity.

Three-dimensional (3D) pseudohalide rare-earth double perovskites (PREDPs) have garnered significant attention for their versatile physical properties, including ferroelectricity, ferroelasticity, large piezoelectric responses, and circularly polarized luminescence. However, their potential for X-ray detection remains unexplored, and the low Curie temperature (TC) limits the performance window for PREDP ferroelectrics. Here, by applying the chemical regulation strategies involving halogen substitution on the organic cation and Rb/Cs substitution to the PREDP [(R)-M3HQ]2RbEu(NO3)6 [(R)-M3HQ=(R)-N-methyl-3-hydroxylquinuclidinium] with a low TC of 285 K, a novel 3D PREDP ferroelectric [(R)-CM3HQ]2CsEu(NO3)6 [(R)-CM3HQ=(R)-N-chloromethyl-3-hydroxylquinuclidinium] are successfully synthesized, for which the TC reaches 344 K. More importantly, such a strategy endowed [(R)-CM3HQ]2CsEu(NO3)6 with notable X-ray detection capabilities. Centimeter-sized [(R)-CM3HQ]2CsEu(NO3)6 single crystals fabricated from aqueous solutions demonstrated a sensitivity of 1307 μC Gyair -1 cm-2 and a low detectable dose rate of 152 nGyair s-1, the highest sensitivity reported for hybrid double perovskite ferroelectric detectors. This work positions PREDPs as promising candidates for the next generation of eco-friendly optoelectronic materials and also offers substantial insights into the interaction between structure, composition, and functionality in ferroelectric materials.

Exploring Aqueous Solution‐Processed Pseudohalide Rare‐Earth Double Perovskite Ferroelectrics toward X‐Ray Detection with High Sensitivity

AbstractThree‐dimensional (3D) pseudohalide rare‐earth double perovskites (PREDPs) have garnered significant attention for their versatile physical properties, including ferroelectricity, ferroelasticity, large piezoelectric responses, and circularly polarized luminescence. However, their potential for X‐ray detection remains unexplored, and the low Curie temperature (TC) limits the performance window for PREDP ferroelectrics. Here, by applying the chemical regulation strategies involving halogen substitution on the organic cation and Rb/Cs substitution to the PREDP [(R)‐M3HQ]2RbEu(NO3)6 [(R)‐M3HQ=(R)‐N‐methyl‐3‐hydroxylquinuclidinium] with a low TC of 285 K, a novel 3D PREDP ferroelectric [(R)‐CM3HQ]2CsEu(NO3)6 [(R)‐CM3HQ=(R)‐N‐chloromethyl‐3‐hydroxylquinuclidinium] are successfully synthesized, for which the TC reaches 344 K. More importantly, such a strategy endowed [(R)‐CM3HQ]2CsEu(NO3)6 with notable X‐ray detection capabilities. Centimeter‐sized [(R)‐CM3HQ]2CsEu(NO3)6 single crystals fabricated from aqueous solutions demonstrated a sensitivity of 1307 μC Gyair−1 cm−2 and a low detectable dose rate of 152 nGyair s−1, the highest sensitivity reported for hybrid double perovskite ferroelectric detectors. This work positions PREDPs as promising candidates for the next generation of eco‐friendly optoelectronic materials and also offers substantial insights into the interaction between structure, composition, and functionality in ferroelectric materials.

Growth and thickness effect of -oriented ternary 0.06Pb(Mn1/3Nb2/3)O3-0.94Pb(Zr0.48Ti0.52)O3 ferroelectric thin films on silicon substrate by RF sputtering

The development of advanced piezoelectric thin films with large piezoelectric response on silicon substrate is a crucial technology for piezoelectric microelectromechanical systems applications. In this work, high-quality <100>-oriented 0.06Pb(Mn1/3Nb2/3)O3-0.94Pb(Zr0.48Ti0.52)O3 (PMN-PZT) thin films were grown on the Pt/Ti/SiO2/Si substrate by sputtering. X-ray diffraction, scanning electron microscopy, and piezoresponse force microscopy were utilized to characterize the phase, morphologies, and domain structures. The growth parameters were optimized and thickness-dependent electrical properties were established. Well-crystalized micron-thick PMN-PZT films with high remnant polarization of 49 μC/cm2 and giant piezoelectric coefficient (d33) up to 484 pC/N (about twice of the polycrystalline PMN-PZT thin film and thrice of the Pb(Zr0.52Ti0.48)O3 thin film) were obtained. The excellent electrical properties make it highly advantageous for applications in MEMS devices.

High Frequency Ultrasound Transducer Based on Sm-Doped Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 Ceramic for Intravascular Ultrasound Imaging.

Sm-doped Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-0.28PT) ceramic has been reported to exhibit very large piezoelectric response (d33~1300 pC/N) that can be comparable with PMN-0.30PT single crystal. Based on the Sm-doped PMN-0.28PT ceramics, a high frequency ultrasound transducer with the center frequency above 30 MHz has been designed and fabricated for intravascular ultrasound imaging, and the performance of the transducer was investigated via ultrasound pulse-echo tests. Further, for a porcine vessel wall, the 2D and 3D ultrasound images were constructed using signal acquisition and processing from the fabricated high-frequency transducer. The obtained details of the vessel wall by the IVUS transducer indicate that Sm-doped PMN-0.28PT ceramic is a promising candidate for high frequency transducers.

Metal-Free Perovskite Ferroelectrics with the Most Equivalent Polarization Axes.

Ferroelectricity in metal-free perovskites (MFPs) has emerged as an academic hotspot for their lightweight, eco-friendly processability, flexibility, and degradability, with considerable progress including large spontaneous polarization, high Curie temperature, large piezoelectric response, and tailoring coercive field. However, their equivalent polarization axes as a key indicator are far from enough, although multiaxial ferroelectrics are highly preferred for performance output and application flexibility that profit from as many equivalent polarization directions as possible with easier reorientation. Here, by implementing the synergistic overlap of regulating anionic geometries (from spherical I- to octahedral [PF6]- and to tetrahedral [ClO4]- or [BF4]-) and cationic asymmetric modification, we successfully designed multiaxial MFP ferroelectrics CMDABCO-NH4-X3 (CMDABCO = N-chloromethyl-N'-diazabicyclo[2.2.2]octonium; X = [ClO4]- or [BF4]-) with the lowest P1 symmetry. More impressively, systemic characterizations indicate that they possess 24 equivalent polarization axes (Aizu notations of 432F1 and m3̅mF1, respectively)─the maximum number achievable for ferroelectrics. Benefiting from the multiaxial feature, CMDABCO-NH4-[ClO4]3 has been demonstrated to have excellent piezoelectric sensing performance in its polycrystalline sample and prepared composite device. Our study provides a feasible strategy for designing multiaxial MFP ferroelectrics and highlights their great promise for use in microelectromechanical, sensing, and body-compatible devices.

Origins of the large piezoelectric response of samarium-doped lead magnesium niobate–lead titanate ceramics

Origins of the large piezoelectric response of samarium-doped lead magnesium niobate–lead titanate ceramics

Biodegradable ferroelectric molecular crystal with large piezoelectric response.

Transient implantable piezoelectric materials are desirable for biosensing, drug delivery, tissue regeneration, and antimicrobial and tumor therapy. For use in the human body, they must show flexibility, biocompatibility, and biodegradability. These requirements are challenging for conventional inorganic piezoelectric oxides and piezoelectric polymers. We discovered high piezoelectricity in a molecular crystal HOCH2(CF2)3CH2OH [2,2,3,3,4,4-hexafluoropentane-1,5-diol (HFPD)] with a large piezoelectric coefficient d33 of ~138 picocoulombs per newton and piezoelectric voltage constant g33 of ~2450 × 10-3 volt-meters per newton under no poling conditions, which also exhibits good biocompatibility toward biological cells and desirable biodegradation and biosafety in physiological environments. HFPD can be composite with polyvinyl alcohol to form flexible piezoelectric films with a d33 of 34.3 picocoulombs per newton. Our material demonstrates the ability for molecular crystals to have attractive piezoelectric properties and should be of interest for applications in transient implantable electromechanical devices.

Enhanced Piezoelectric Response at Nanoscale Vortex Structures in Ferroelectrics.

The piezoelectric response is a measure of the sensitivity of a material's polarization to stress or its strain to an applied field. Using in operando X-ray Bragg coherent diffraction imaging, we observe that topological vortices are the source of a 5-fold enhancement of the piezoelectric response near the vortex core. The vortices form where several low-symmetry ferroelectric phases and phase boundaries coalesce. Unlike bulk ferroelectric solid solutions in which a large piezoelectric response is associated with coexisting phases in the proximity of the triple point, the largest responses for pure BaTiO3 at the nanoscale are in spatial regions of extremely small spontaneous polarization at vortex cores. The response decays inversely with polarization away from the vortex, analogous to the behavior in bulk ceramics as the cation compositions are varied away from the triple point. We use first-principles-based molecular dynamics to augment our observations, and our results suggest that nanoscale piezoelectric materials with a large piezoelectric response can be designed within a parameter space governed by vortex cores. Our findings have implications for the development of next-generation nanoscale piezoelectric materials.

Large piezoelectric responses and ultra-high carrier mobility in Janus HfGeZ3H (Z = N, P, As) monolayers: a first-principles study.

Breaking structural symmetry in two-dimensional layered Janus materials can result in enhanced new phenomena and create additional degrees of piezoelectric responses. In this study, we theoretically design a series of Janus monolayers HfGeZ3H (Z = N, P, As) and investigate their structural characteristics, crystal stability, piezoelectric responses, electronic features, and carrier mobility using first-principles calculations. Phonon dispersion analysis confirms that HfGeZ3H monolayers are dynamically stable and their mechanical stability is also confirmed through the Born-Huang criteria. It is demonstrated that while HfGeN3H is a semiconductor with a large bandgap of 3.50 eV, HfGeP3H and HfGeAs3H monolayers have narrower bandgaps being 1.07 and 0.92 eV, respectively. When the spin-orbit coupling is included, large spin-splitting energy is found in the electronic bands of HfGeZ3H. Janus HfGeZ3H monolayers can be treated as piezoelectric semiconductors with the coexistence of both in-plane and out-of-plane piezoelectric responses. In particular, HfGeZ3H monolayers exhibit ultra-high electron mobilities up to 6.40 × 103 cm2 V-1 s-1 (HfGeAs3H), indicating that they have potential for various applications in nanoelectronics.

Organic-Inorganic Rare-Earth Double Perovskite Ferroelectric with Large Piezoelectric Response and Ferroelasticity for Flexible Composite Energy Harvesters.

Hybrid organic-inorganic perovskite (HOIP) ferroelectric materials have great potential for developing self-powered electronic transducers owing to their impressive piezoelectric performance, structural tunability and low processing temperatures. Nevertheless, their inherent brittle and low elastic moduli limit their application in electromechanical conversion. Integration of HOIP ferroelectrics and soft polymers is a promising solution. In this work, a hybrid organic-inorganic rare-earth double perovskite ferroelectric, [RM3HQ]2 RbPr(NO3 )6 (RM3 HQ = (R)-N-methyl-3-hydroxylquinuclidinium) is presented, which possesses multiaxial nature, ferroelasticity and satisfactory piezoelectric properties, including piezoelectric charge coefficient (d33 ) of 102.3 pCN-1 and piezoelectric voltage coefficient (g33 ) of 680×10-3 V m N-1 . The piezoelectric generators (PEG) based on composite films of [RM3HQ]2 RbPr(NO3 )6 @polyurethane (PU) can generate an open-circuit voltage (Voc ) of 30V and short-circuit current (Isc ) of 18µA, representing one of the state-of-the-art PEGs to date. This work has promoted the exploration of new HOIP ferroelectrics and their development of applications in electromechanical conversion devices.

Superior high-temperature piezoelectric response of lead-free Ga-doped BiFeO3−BaTiO3 ceramic with multiphase coexistence

Herein, the (1 − x)BiFe0.97Ga0.03O3 − xBaTiO3 (BF97BG3 − xBT) ceramics were prepared by modulating the content of BT using (Bi0.5Li0.5)TiO3 and MnO2 as sintering additives. A record d33 of 533.2 pC/N is achieved in the BF97BG3 − 0.34BT ceramic at a real-time depolarization temperature (Tdr) of 314.7 °C, indicating the piezoelectric characteristic in the actual operating state. A multiphase coexistence structure involving rhombohedral (R), tetragonal (T), cubic (C) phases is produced in the BF97BG3-0.34BT ceramic, which contributes to the large piezoelectric response. The in-situ X-ray diffraction (XRD) results demonstrate that the crystal structure of BF97BG3-0.34BT ceramic does not change with the increase of temperature. Moreover, the formation of nanodomain morphology and a large number of polar nanoregions (PNRs) can weaken the energy barrier and polarization anisotropy, enhance the polarization rotation, and thus improve the piezoelectric response of the ceramic. This work provides an effective strategy to achieve large high-temperature piezoelectric response by constructing nanoscale multiphase coexistence.

Electromechanical properties of [0 0 1]‐textured Mn–PMN–PZT ceramics under uniaxial pressure

AbstractDielectric, ferroelectric, and piezoelectric properties of both random and textured Mn–PMN–PZT ceramics were characterized under uniaxial stress. Textured ceramics exhibit a large piezoelectric response under uniaxial pressure; the bias field piezoelectric constant is higher than 700 pC/N when pressure is below 50 MPa. Moreover, textured ceramics also show better depolarization resistance under uniaxial stress fields; overall, 30% of the origin performance will remain when stress approaches 200 MPa, but for random ceramics, it is only 10%. The ferroelectricity of both random and textured ceramics is suppressed by uniaxial compression. Ec, Pr, Ei, and dissipation energy all decrease with increasing uniaxial stress. In addition, phase‐field simulation was used to better understand the polarization‐changing effects on piezoelectric and dielectric performance. The uniaxial stress causes polarization rotation and increases the angle between polarization and the electric field, which is an important factor leading to the increase of the dielectric constant.

Domain reorientation and electric-field-induced phase transition in (K,Na)(Nb,Sb)O3-(Bi,Na)ZrO3 piezoceramics

Polymorphic phase transition boundary (PPB) strategy is effective in designing high-performance piezoelectric materials in (K0.5Na0.5)NbO3 (KNN)-based systems. However, the underlying mechanism of large piezoelectric response in KNN-based is still blurry and thus needs to be explored properly. In this paper, it is found that the domain reorientation becomes easier and more sufficient in the KNN-based ceramics with two-phase coexistence. Moreover, in situ transmission electron microscope experiments disclose the occurrence of a new intermediate phase under an external electric filed, which could relieve the internal stress generated by the domain reorientation and then facilitate the further domain switching along the electric field direction. The enhanced domain reorientation contributes to the high piezoelectric response in PPB region (d33 = 438 pC/N, kp = 48%, d33* = 520 p.m./V at 1.5 kV/mm). Our work provides an in-depth understanding of the contribution of the domain switching and electric-filed-induced phase transition to piezoelectric properties in KNN-based ceramics, which shall benefit the design of new lead-free high-performance piezoelectric materials.

Piezoelectric self-power supply driven by ferroelastic host–guest supramolecule with considerable electromechanical conversion capability

Crown ether supramolecules with host–guest structure bring the two most advanced application categories, namely information storage and energy conversion. The former was awarded the 2016 Nobel Prize in Chemistry, but the latter has thus far exhibited suboptimal electromechanical conversion properties. Enhancing the piezoelectric properties of such supramolecules has become a continuous and fascinating challenge. Here, we have made breakthrough progress in a crown ether-based ferroelastic supramolecular rotator [(N,N-dimethylethylenediammonium)(18-crown-6)]BF4 (MCBF) under the guidance of the crystallographic engineering. MCBF shows the record-high piezoelectric voltage coefficient (∼1000 × 10-3 V m N−1) and piezoelectric coefficient (∼46.1 pC N−1), which represent respectively improvements of 41.7% and 9.8% compared to the latest reported counterpart (J. Am. Chem. Soc. 145 (2023) 3187–3195). Notably, theoretical calculations elucidate that the ferroelasticity of MCBF contributes to its large piezoelectric response. In addition, an energy harvesting device is successfully achieved for the first time to evaluate its potential as a piezoelectric self-power supply, and LEDs are successfully lit by harvesting mechanical energy. This work takes an important step towards artificial supramolecular machines and arouses broad interest in self-powered flexible devices.

Engineering Ferroelectricity and Large Piezoelectricity in h-BN.

Hexagonal boron nitride (h-BN) is a well-known layered van der Waals (vdW) material that exhibits no spontaneous electric polarization due to its centrosymmetric structure. Extensive density functional theory (DFT) calculations are used to demonstrate that doping through the substitution of B by isovalent Al and Ga breaks the inversion symmetry and induces local dipole moments along the c-axis, which promotes a ferroelectric (FE) alignment over antiferroelectric. For doping concentrations below 25%, a "protruded layered" structure in which the dopant atoms protrude out of the planar h-BN layers is energetically more stable than the flat layered structure of pristine h-BN or a wurtzite structure similar to w-AlN. The computed polarization, between 7.227 and 21.117 μC/cm2, depending on dopant concentration and the switching barrier (16.684 and 45.838 meV/atom) for the FE polarization reversal are comparable to that of other well-known FEs. Interestingly, doping of h-BN also induces a large negative piezoelectric response in otherwise nonpiezoelectric h-BN. For example, we compute d33 of -24.214 pC/N for Ga0.125B0.875N, which is about 5 times larger than that of pure w-AlN (5 pC/N), although the computed e33 (-1.164 C/m2) is about 1.6 times lower than that of pure w-AlN (1.462 C/m2). Because of the layered structure, the rather small elastic constant C33 provides the origin of the large d33. Moreover, doping makes h-BN an electric auxetic piezoelectric. We also show that ferroelectricity in doped h-BN may persist down to its trilayer, which indicates high potential for applications in FE nonvolatile memories.

La-doped PMN–PT transparent ceramics with ultra-high electro-optic effect and its application in optical devices

Transparent electro-optic (EO) ceramics of La-doped 0.75Pb(Mg_1/3Nb_2/3)O₃–0.25PbTiO₃ (0.75PMN–0.25PT) were prepared successfully. High transparency of 69% in the near-infrared (IR) wavelength (1550 nm) was achieved at 2 mol% La doping, meanwhile it shows an extremely high quadratic EO coefficient of 45.4×10⁻¹⁶ m²·V⁻², which is indispensable for applications in EO devices. The distribution of a polar nanodomain structure of the samples experiences disorder–order–disorder evolution in a La doping range. It is found that a parallelly-stacked polar nanodomain structure with an easier and faster polarization switching in the 2 mol% La-doped sample suggests that an ordering distribution of polar nanoregions would be critical to inducing large EO effect, transparency, and piezoelectric response. A triple-cavity tunable optical filter (TOF) with a single transmission peak and a tuning voltage below 30 V in a tuning range of 190–197 THz was designed based on our ceramics. The work is believed to bridge the relationship among doping-engineering, EO properties, and polarization behavior, which would guide the further optimization of transparent EO ceramics.

The First Ring Enlargement Induced Large Piezoelectric Response in a Polycrystalline Molecular Ferroelectric.

Inorganic ferroelectrics have long dominated research and applications, taking advantage of high piezoelectric performance in bulk polycrystalline ceramic forms. Molecular ferroelectrics have attracted growing interest because of their environmental friendliness, easy processing, lightweight, and good biocompatibility, while realizing the considerable piezoelectricity in their bulk polycrystalline forms remains a great challenge. Herein, for the first time, through ring enlargement, a molecular ferroelectric 1-azabicyclo[3.2.1]octonium perrhenate ([3.2.1-abco]ReO4 ) with a large piezoelectric coefficient d33 up to 118 pC/N in the polycrystalline pellet form is designed, which is higher than that of the parent 1-azabicyclo[2.2.1]heptanium perrhenate ([2.2.1-abch]ReO4 , 90 pC/N) and those of most molecular ferroelectrics in polycrystalline or even single crystal forms. The ring enlargement reduces the molecular strain for easier molecular deformation, which contributes to the higher piezoelectric response in [3.2.1-abco]ReO4 . This work opens up a new avenue for exploring high piezoelectric polycrystalline molecular ferroelectrics with great potential in piezoelectric applications.

Enhanced piezoelectric properties in coarse-grained 0.7Bi(Fe0.9985Mn0.0015)O3-0.3BaTiO3 ceramics

The lead-free BiFeO3-BaTiO3 (BF-BT) based ceramics with large piezoelectric coefficient (d33) have been desired for promising applications in high-temperature fields. Herein, the 0.7Bi(Fe0.9985Mn0.0015)O3-0.3BaTiO3 ceramics with different grain sizes are intentionally prepared by solid-state method, and a large d33 (232 pC/N) and high Curie temperature Tc (501 °C) are simultaneously achieved in the case of large grain size (>9 µm). X-ray diffraction and Rietveld refinement analyses indicate that these coarse-grained samples possess stronger rhombohedral distortion and enlarged lattice parameter compared to fine-grained samples, which make domain switching easier and give rise to the increase in strain. As a result, the piezoelectric and ferroelectric properties of such samples are significantly improved with increasing grain size from 3.05 µm to 9.07 µm. In addition, electric domain configuration and field-induced strain further prove that the strong piezoelectric response in coarse-grained samples is attributed mainly to enhanced non-180° domain mobility. This study reveals the origin of large piezoelectric response in coarse-grained BF-BT ceramics, and proposes an effective approach to improve the piezoelectric properties of BF-BT ceramics.

Simultaneously enhanced piezoelectric response and depolarization temperature in BNT-7BT ceramics with simple composition via optimizing sintering temperature

For (Bi0.5Na0.5)TiO3-based ceramics, one of the obstacles limiting their actual application is the incompatibility of a large piezoelectric response d33 with a low depolarization temperature Td. In this work, a high d33 of 186 pC/N and a Td of 133 °C are achieved simultaneously in unmodified 0.93(Bi0.5Na0.5) TiO3–0.07BaTiO3 (BNT-7BT) ceramics only via optimizing sintering temperature. Structural and microstructural analyses show that grain size and relative content of P4bm and R3c phases in BNT-7BT ceramics can be regulated by tuning the sintering temperature (Tsinter = 1100 °C, 1120 °C, 1140 °C, 1160 °C, and 1180 °C). Thus, high sintering temperature is not only able to increase the grain size to promote the domains switching for higher the piezoelectric response, but also to enhance the ratio of R3c/P4bm phase so as to improve ferroelectric-relaxor transition temperature that defer the depolarization. Hence, the present work provides a simple and effective method for optimizing the piezoelectric properties of (Bi0.5Na0.5)TiO3-based ceramics.