High-performance Piezoelectric Materials Research Articles

Giant piezoelectricity in antiferromagnetic CrS2 and CrSe2 monolayers

Abstract Two-dimensional (2D) materials, particularly transition metal dichalcogenides (TMDs), have garnered significant attention in the nanoscale piezoelectric field due to their high crystallinity and ability to withstand large strains. Through density-functional theory calculations, we have discovered that monolayer H-phase CrS2 and CrSe2 exhibit antiferromagnetic semiconducting properties, in contrast to the previously held belief that they were nonmagnetic (NM) semiconductors. While the piezoelectric coefficients of NM CrS2 and CrSe2 are comparable to those of MoS2, their antiferromagnetic ground states demonstrate significantly enhanced piezoelectric coefficients ( d 11 ) of 27.66 pm V−1 and 52.36 pm V−1, respectively. These values exceed that of MoS2 by an order of magnitude, marking the highest recorded for TMD materials and the highest in 2D magnetic materials to date. The greatly enhanced piezoelectric responses in the antiferromagnetic states of CrS2 and CrSe2 compared to their NM states arise from three primary factors. Firstly, the displacement of the Wannier center under strain is more pronounced in the antiferromagnetic state, leading to a greater change in dipole moment (enhanced clamped-ion contribution). Secondly, there is a heightened polarization change due to internal atomic distortions (internal-strain term) in response to macroscopic strain in the antiferromagnetic state. Thirdly, the material undergoes a softening of the elastic coefficient in its antiferromagnetic state. These findings open new avenues for designing high-performance piezoelectric and magnetic multifunctional materials.

High performance (K,Na)NbO3-based textured ceramics for piezoelectric energy harvesting

Piezoelectric energy harvesters (PEHs), which can provide sustainable green energy for low-power electronics have received extensive attention in the viewpoint of science and industrialization. In order to achieve large output power of PEHs, high-performance piezoelectric materials are extremely desired. Herein, excellent electromechanical conversion properties of d33 ∼ 447 pC/N, g33 ∼ 30 × 10−3 Vm/N, k33 ∼ 47 % and Suni ∼0.18 % were achieved in <001> grain aligned KNN-based lead-free ceramics with a favorable rhombohedral (R), orthorhombic (O) and tetragonal (T) multiphase structure. The superior electromechanical conversion properties can be attributed to grain orientation and crystal symmetry controlled anisotropy, and multiphase coexistence significantly decreased poling energy barrier, as well asthe flexible response of the nanometer domains to external stimuli. The PEHs fabricated using the optimal performance KNN-based textured ceramics exhibit high output power of 0.46 mW and power density of 6.7 mW/cm3 at a resonant frequency of 41 Hz, which is associated with the large k33 (∼47 %) and figure-of-merit (d33×g33 ∼ 13.4 × 10−12 m2/N) values. The output power can actually light up more than 145 commercial LEDs, demonstrating great potential of KNN-based PEHs to power wireless sensors.

Mechanical properties and multi-field ferroelastic response of Nb/Mn Co-doped CaBi4Ti4O15 high-temperature ferroelectric ceramics

CaBi4Ti4O15 (CBT) ceramics are promising piezoelectric materials that have been widely studied for high-temperature applications. Despite significant advancements in the electrical performance of CBT ceramics, the understanding of their mechanical behaviors remains limited, which is unfavorable for designing ceramics with high stability and reliability during high-temperature service. This work investigated the mechanical properties and fracture behaviors of Nb/Mn co-doped CaBi4Ti4O15 (CBTNM) with various doping levels, focusing on stress-strain responses and ferroelastic deformation behaviors under uniaxial compression and multi-field coupling conditions. HRTEM analysis reveals small-scale layered domain wall structures on the surface of plate-like grains. The fracture and compressive strengths of CBTNM ceramics initially decrease and then increase with an increase in doping content, and the underlying mechanisms are related to grain size, defects, and densification. CBTNM ceramics exhibit nonlinear stress-strain responses due to ferroelastic deformation under compressive loading, and the resultant irreversible domain switching strain increases with an increase in doping content, while poling can further increase the residual strain. Under multi-field loading conditions, CBTNM ceramics undergo more ferroelastic deformation events and exhibit larger residual strain. The micro-cracks, pores, complicated fracture modes, and degraded fracture surfaces with fragmental and rough features are mainly responsible for the lower elastic modulus and inferior mechanical response. This work enhances our understanding of the mechanical behaviors of high-temperature piezoelectric ceramics and provides guidance for designing high-performance piezoelectric materials for complex environmental applications.

Enhancing piezoelectric properties of BiScO3-PbTiO3 ceramics via- incorporation of Bi(Zn1/2Ti1/2)O3 with high spontaneous polarization

High-performance piezoelectric materials are the core elements for the fabrication piezoelectric transducers and actuators. In recent years, there has been an increasing demand for piezoelectric materials with both high operational temperature and large piezoelectricity. However, the conventional approach of soft doping to enhance the piezoelectric response often results in a reduction in Curie temperature. To address this issue, we incorporated Bi(Zn1/2Ti1/2)O3 with a large spontaneous polarization (Ps ∼ 100 µC/cm2) and high Curie temperature (Tc ∼ 1380 °C) into BiScO3-PbTiO3 ceramics to improve the piezoelectric response while maintaining high Tc. The newly developed 0.08Bi(Zn1/2Ti1/2)O3-0.335BiScO3-0.585PbTiO3 ceramic exhibits impressive properties including a high d33 value of 585 pC/N (increased by ∼ 33 % compared to the 0.36BiScO3-0.64PbTiO3 ceramics), an electromechanical coupling coefficient k33 of 0.75, a dielectric constant ε′ of 2380, a relatively high Tc of 421 °C. These remarkable improvements hold great promise for advancing high-temperature piezoelectric devices.

Defect dipole stretching enables ultrahigh electrostrain.

Piezoelectric actuators have been extensively utilized as micro-displacement devices because of their advantages of large output displacement, high sensitivity, and immunity to electromagnetic interference. Here, we propose a straightforward approach to design <110>-oriented defect dipoles by introducing A-site vacancies and oxygen vacancies in (K0.48Na0.52)0.99NbO2.995 ceramics. As a result, we achieve ultrahigh electrostrains of 0.7% at 20 kV cm-1 (with an effective piezoelectric strain coefficient d33* = 3500 pm V-1), outperforming the performance of existing piezoelectric ceramics at the same driving field. The exceptional electrostrain is primarily attributed to the large stretching of defect dipoles when subjected to an applied electric field, a phenomenon that has been experimentally confirmed. Moreover, the strong interaction between these defect dipoles and <110> spontaneous polarizations plays a critical role in minimizing hysteresis and ensuring excellent fatigue resistance. Our findings present a practical and effective strategy for developing high-performance piezoelectric materials tailored for advanced actuator applications.

0.98(K0.5Na0.5)NbO3–0.02(Bi0.5Na0.5)(Zr0.85Sn0.15)O3 Single Crystals Grown by the Seed-Free Solid-State Crystal Growth Method and Their Characterization

(K0.5Na0.5)NbO3-based single crystals are of interest as high-performance lead-free piezoelectric materials, but conventional crystal growth methods have some disadvantages such as the requirement for expensive Pt crucibles and difficulty in controlling the composition of the crystals. Recently, (K0.5Na0.5)NbO3-based single crystals have been grown by the seed-free solid-state crystal growth method, which can avoid these problems. In the present work, 0.98(K0.5Na0.5)NbO3–0.02(Bi0.5Na0.5)(Zr0.85Sn0.15)O3 single crystals were grown by the seed-free solid-state crystal growth method. Sintering aids of 0.15 mol% Li2CO3 and 0.15 mol% Bi2O3 were added to promote single crystal growth. Pellets were sintered at 1150 °C for 15–50 h. Single crystals started to appear from 20 h. The single crystals grown for 50 h were studied in detail. Single crystal microstructure was studied by scanning electron microscopy of the as-grown surface and cross-section of the sample and revealed porosity in the crystals. Electron probe microanalysis indicated a slight reduction in K and Na content of a single crystal as compared to the nominal composition. X-ray diffraction shows that the single crystals contain mixed orthorhombic and tetragonal phases at room temperature. Raman scattering and impedance spectroscopy at different temperatures observed rhombohedral–orthorhombic, orthorhombic–tetragonal and tetragonal–cubic phase transitions. Polarization–electric field (P–E) hysteresis loops show that the single crystal is a normal ferroelectric material with a remanent polarization (Pr) of 18.5 μC/cm2 and a coercive electrical field (Ec) of 10.7 kV/cm. A single crystal presents d33 = 362 pC/N as measured by a d33 meter. Such a single crystal with a large d33 and high Curie temperature (~370 °C) can be a promising candidate for piezoelectric devices.

Boosting piezoelectric response and electric-field induced strain in PMN-PT relaxor ferroelectrics

High-performance piezoelectric materials are essential for diverse electromechanical devices, from actuators to sensors and transducers. Here, we synthesized Ce2O3-doped Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (xCe-PMNT29) solid solutions via conventional solid-state methods. In the x = 2.5 % modified composition, we achieved a notable electrostrain-hysteresis trade-off, enhancing electrostrain (0.2 %), equivalent piezoelectric coefficient d33* (1701 pm V–1 at 3 kV cm–1), and reducing strain hysteresis to 8.1 %. Additionally, direct high-temperature piezoelectric characterizations revealed real-time variations in piezoelectric coefficient (d33) and the actual depolarization temperature, with d33 reaching 859 pC N−1 at 53 °C and planar electromechanical coupling coefficient (kp) exceeding 70 % within 30−85 °C. Leveraging x-ray diffraction (XRD) and piezoelectric force microscopy (PFM), we elucidated synergistic effects between complex nanodomains and local structural heterogeneity, enhancing piezoelectric activity. This study presents a promising approach for improving electromechanical performance and electrostrain in ferroelectrics, with significant potential for practical piezoelectric applications.

Ultrahigh strain and superior temperature stability in lead-free ceramics via synergetic texture technique and phase structure engineering

Lead-free piezoelectric ceramics with large strain response and good temperature stability are highly required for actuator applications. However, the search for lead-free ceramics with both enhanced strain and reduced thermal-dependent behavior is a great challenge. In this work, by employing templated grain growth technique and elaborately modulate the phase structure, large unipolar strain of 0.30 %, low strain hysteresis Hs ∼ 12 %, along with small strain variation 11.8 % between 20 and 100 °C are achieved in (001)C-oriented (Ba0.95Ca0.05)(Sn0.04Ti0.96)O3 ceramics, being the optimal level of BaTiO3 family. It is revealed the ceramics exhibit a coexistence of orthorhombic and tetragonal phases. The inherent piezoelectric anisotropy of orthorhombic phase, the reversible a→c domain switch, along with the refined non-180° domain structures contribute to the remarkable electrostrain characteristic. This study proposed a promising strategy to develop high performance piezoelectric materials for actuator applications.

Flexible Piezoelectric Sensor Based on Two-Dimensional Topological Network of PVDF/DA Composite Nanofiber Membrane

Owing to the robust scalability, ease of control and substantial industrial applications, the utilization of electrospinning technology to produce piezoelectric nanofiber materials demonstrates a significant potential in the development of wearable products including flexible wearable sensors. However, it is unfortunate that the attainment of high-performance piezoelectric materials through this method remains a challenging task. Herein, a high-performance composite nanofiber membrane with a coherent and uniformly dispersed two-dimensional network topology composed of polyvinylidene fluoride (PVDF)/dopamine (DA) nanofiber membranes and ultrafine PVDF/DA nanofibers was successfully fabricated by the electrospinning technique. Based on the evidence obtained from simulations, experimental and theoretical results, it was confirmed that the unique structure of the nanofiber membrane significantly enhances the piezoelectric performance. The present PVDF/DA composite nanofibers demonstrated a remarkable piezoelectric performance such as a wide response range (1.5–40 N), high sensitivity to weak forces (0–4 N, 7.29 V N−1), and outstanding operational durability. Furthermore, the potential application of the present PVDF/DA membrane as a flexible wearable sensor for monitoring human motion and subtle physiological signals has also been validated. This work not only introduces a novel strategy for the application of electrospun nanofibers in sensors but also provides new insights into high-performance piezoelectric materials.Graphical

Autoencoded chemical feature interaction machine learning method boosting performance of piezoelectric catalytic process

Piezoelectric catalytic process can reduce energy consumption in water treatment processes. However, the design of high-performance piezoelectric materials and the search for operating parameters are still challenging tasks. This study explored a modified machine learning (ML) technology, autoencoded chemical feature interaction machine learning (AutoCFI-ML), by employing the autoencoder and factorization machine for designing piezoelectric materials and optimizing operating parameters to improve the performance of the piezoelectric catalytic process. This method improved the performance of regression-based ML methods through carefully designed chemical features boost. The extreme gradient boosting (XGBoost) model was considered the optimal model with R2 = 0.88 and RMSE = 1.02. The catalyst composition, initial pH value, catalyst/pollutant dosage ratio, and ultrasound power were identified as relatively important features among the 34 features. When targeting RhB or phenol as the typical pollutant, the errors between the prediction results of the trained AutoCFI-XGBoost model and the experimental results in the reverse experiment were both less than 10%. This work provides novel insights and improvement strategies by ML technique to design piezoelectric catalysts and optimize operating parameters for enhancing the performance of piezoelectric catalytic process, improving the application potential of the piezoelectric catalytic process.

Utilizing a High-Performance Piezoelectric Nanocomposite as a Self-Activating Component in Piezotronic Artificial Mechanoreceptors.

Challenges such as poor dispersion and insufficient polarization of BaTiO3 (BTO) nanoparticles (NPs) within poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) composites have hindered their piezoelectricity, limiting their uses in pressure sensors, nanogenerators, and artificial sensory synapses. Here, we introduce a high-performance piezoelectric nanocomposite material consisting of P(VDF-TrFE)/modified-BTO (mBTO) NPs for use as a self-activating component in a piezotronic artificial mechanoreceptor. To generate high-performance piezoelectric nanocomposite materials, the surface of BTO is hydroxylated, followed by the covalent attachment of (3-aminopropyl)triethoxysilane to improve the dispersibility of mBTO NPs within the P(VDF-TrFE) matrix. We also aim to enhance the crystallization degree of P(VDF-TrFE), the efficiency characteristics of mBTO, and the poling efficiency, even when incorporating small amounts of mBTO NPs. The piezoelectric potential mechanically induced from the P(VDF-TrFE)/mBTO NPs nanocomposite was three times greater than that from P(VDF-TrFE) and twice as high as that from the P(VDF-TrFE)/BTO NPs nanocomposite. The piezoelectric potential generated by mechanical stimuli on the piezoelectric nanocomposite was utilized to activate the synaptic ionogel-gated field-effect transistor for the development of self-powered piezotronics artificial mechanoreceptors on a polyimide substrate. The device successfully emulated fast-adapting (FA) functions found in biological FA mechanoreceptors. This approach has great potential for applications to future intelligent tactile perception technology.

Centrosymmetry-Breaking Morphotropic Phase Boundary: A Pathway to Highly Sensitive and Strong Pressure-Responsive Nonlinear Optical Switches.

The quest for high-performance piezoelectric materials has been synonymous with the pursuit of the morphotropic phase boundary (MPB), yet the full potential of MPBs remains largely untapped outside of the realm of ferroelectrics. In this study, we reveal a new class of MPB by creating continuous molecular-based solid solutions between centro- and noncentrosymmetric compounds, exemplified by (tert-butylammonium)1-x(tert-amylammonium)xFeCl4 (0 ≤ x ≤ 1), where the MPB is formed due to disorder of molecular cations. Near the MPB, we discovered an exceptionally sensitive nonlinear optical material in the centrosymmetric phase, capable of activation at pressures as low as 0.12-0.27 GPa, and producing tunable second-harmonic generation (SHG) signals from zero to 18.8 times that of KH2PO4 (KDP). Meanwhile, synchrotron diffraction experiments have unveiled a third competing phase (P212121) appearing at low pressure, forming a triple-phase point near the MPB, thereby providing insight into the mechanism underpinning the nonlinear optical (NLO) switch behavior. These findings highlight the opportunity to harness exceptional physical properties in symmetry-breaking solid solution systems by strategically designing novel MPBs.

Mesocrystalline SrTiO3/CaTiO3 nanocomposites with 3D heteroepitaxial interfaces, superior piezoresponse and high Curie temperature

Ferroelectric mesocrystalline nanocomposites are promising piezoelectric nanomaterials due to the presence of three-dimensional (3-D) heteroepitaxial interfaces, rendering superior piezoelectric and dielectric responses due to lattice strain at the interface. Herein, we describe the synthesis of mesocrystalline SrTiO3/CaTiO3 (ST/CT) nanocomposites via a two-step topochemical process by using layered titanate H1.07Ti1.73O4·nH2O (HTO), as a precursor, and demonstrate the influence of synthesis parameters on nanostructure, morphology, piezoelectric response and dielectric behavior. The mesocrystalline ST/CT nanocomposites are formed by in-situ topotactic structural transformation, consisting of [110]-oriented ST nanocrystals and [001]-oriented CT nanocrystals with high-density 3-D heteroepitaxial interfaces. The presence of 3-D heteroepitaxial interfaces introduces lattice strain at the interface, leading to an enormously enhanced piezoelectric response with a d33* value of 301 p.m./V. Moreover, the Curie temperature of ST phase is significantly increased from −250 °C to 300 °C by introducing lattice strain. It is demonstrated that the piezoresponse depends on lattice mismatch at heteroepitaxial interfaces and optimal lattice mismatch is found to be ∼3.3%, where the largest lattice strain effect and an expected d33* value of about 450 p.m./V could be achieved. These results demonstrate the potential of lattice strain engineering for high-performance lead-free piezoelectric materials.

Asymmetric XMoGeY2 (X = S, Se, Te; Y = N, P, As) monolayers as potential flexible materials for nano piezoelectric devices and nanomedical sensors.

Highly efficient nano piezoelectric devices and nanomedical sensors are in great demand for high-performance piezoelectric materials. In this work, we propose new asymmetric XMoGeY2 (X = S, Se, Te; Y = N, P, As) monolayers with excellent piezoelectric properties, dynamic stability and flexible elastic properties. The piezoelectric coefficients (d11) of XMoGeY2 monolayers range from 2.92 to 8.19 pm V-1. Among them, TeMoGeAs2 exhibits the highest piezoelectric coefficient (d11 = 8.19 pm V-1), which is 2.2 times higher than that of common 2D piezoelectric materials such as 2H-MoS2 (d11 = 3.73 pm V-1). Furthermore, all XMoGeY2 monolayers demonstrate flexible elastic properties ranging from 96.23 to 253.70 N m-1. Notably, TeMoGeAs2 has a Young's modulus of 96.23 N m-1, which is only one-third of that of graphene (336 N m-1). The significant piezoelectric coefficients of XMoGeY2 monolayers can be attributed to their asymmetric structures and flexible elastic properties. This study provides valuable insights into the potential applications of XMoGeY2 monolayers in nano piezoelectric devices and nanomedical sensors.

Deciphering the structural heterogeneity behaviors of (K, Na)NbO[formula omitted]-based piezoelectric ceramics with multi-scale analyses

Inducing local structural heterogeneity is one of the most attractive strategies to enhance the piezoelectricity in lead-free piezoceramics, while the underlying mechanisms have not been well clarified, such as phase coexistence and domain boundary. Here, we mainly focus on analyzing the structure evolution mechanism of 0.96(K0.48Na0.52)(Nb1−xSbx)O3-0.04(Bi0.5Ag0.5)ZrO3 (0≤x≤0.1) (KNN) lead-free piezoelectric ceramics to study the intrinsic structural contributions from chemical modifying and/or alloy replacement. We explore the relation between structural characteristics and physical functionality by combining macro-spectral and micro-heterogeneity characterizations. It was found that Raman- and infrared-active phonon evolutions with respect to the motion of oxygen octahedron reveal the enhanced lattice symmetry when x increases to 0.06, along with the upswing optical electronic transitions. Moreover, we clarify the local heterogeneous structure of ceramics in terms of the spatial distribution of phonon traits on the micron scale accompanied with the atom-resolution polar vector state. The detected nanoscale atomic displacement clusters are directly related to the excellent polarization properties. Additionally, the phonon thermodynamics evolution was investigated in a wide temperature range of 80-720 K with unpolarized and polarized geometries. The detailed phase transition evolution and rhombohedral–orthorhombic–tetragonal multi-phase coexistence have been confirmed with Sb incorporation. The present work boosts the understanding of the compound-structure-functionality relation of KNN-based heterophase coexistent system, which could promote the development of the promising high-performance piezoelectric materials.

Engineering grain orientation and local heterogeneous enable further breakthroughs in piezoelectricity for NaNbO3-based piezoelectric oxides

Eco-friendly NaNbO3 (NN)-based relaxor ferroelectric ceramics with high dielectric constants cannot meet the high piezoelectric activity quality factors (FOMs: d33 × g33) requirements of electromechanically coupled devices. To solve this issue, we successfully improved the piezoelectricity of NN-based relaxor piezoceramics while reducing the dielectric constant based on microstructural tuning by virtue of the chemical design and texturing engineering. Mainly affected by the highly <001>c orientation and relaxor MPB, the obtained novel 88.5NaNbO3–10Ba(Ti0.7Sn0.3)O3–1.5NaSbO3 texture ceramics enjoys an ultrahigh piezoelectric coefficient (d33 = 423 pC/N), reaching a record high in NaNbO3-based lead-free ceramics. Meanwhile, a large FOMs value (d33 × g33 = 13.3·10−12 m2/N) is successfully realized due to the suppression of the dielectric constant. More importantly, the stable phase/domain evolution also encourages excellent temperature stability for piezoelectricity and FOMs. Especially for the piezoelectricity, when the annealing temperature is < 140 °C, the d33 of the 1.5T ceramics can be stabilized ∼ 400 pC/N. Such excellent electrical temperature stability shows more competition in the reported NN-based piezoceramics. This work not only provides a design paradigm for high-performance piezoelectric materials, but also facilitates their development in electromechanical coupling devices.

Wearable Electrospun Piezoelectric Mats Based on a PVDF Nanofiber-ZnO@ZnS Core-Shell Nanoparticles Composite for Power Generation.

This work adopted a strategy to use new functional high-performance piezoelectric materials for sustainable energy production in wearable self-powered electrical devices. An innovative modification in electrospinning was used to produce highly aligned nanofibers. In the nanogenerator, the flexible membrane constituents were tunefully combined. The novel composite nanofibers were made of Poly (vinylidene fluoride) PVDF, loaded with ZnO@ZnS core-shell nanoparticles to achieve a non-brittle performance of the hetero nanoparticles and piezoelectric polymer. A nanofiber mat was inserted between two thermoplastic sheets with conductive electrodes for application in wearable electronic devices. Complete spectroscopic analyses were performed to characterize the nanofiber's material composition. It is shown that the addition of 10 wt % ZnO@ZnS core-shell nanoparticles significantly improved the piezoelectric properties of the nanofibers and simultaneously kept them flexible due to the exceedingly resilient nature of the composite. The superior performance of the piezoelectric parameter of the nanofibrous mats was due to the crystallinity (polar β phase) and surface topography of the mat. The conversion sensitivity of the PVDF device recorded almost 0.091 V/N·mm3, while that of the PVDF-10 wt % ZnO@ZnS composite mat recorded a sensitivity of 0.153 V/N·mm3, which is higher than many flexible nano-generators. These nanogenerators provide a simple, efficient, and cost-effective solution to microelectronic wearable devices.

Enhanced Electromechanical Performance in Lead-free (Na,K)NbO3-Based Piezoceramics via the Synergistic Design of Texture Engineering and Sm-Modification.

Next-generation electromechanical conversion devices have a significant demand for high-performance lead-free piezoelectric materials to meet environmentally friendly requirements. However, the low electromechanical properties of lead-free piezoceramics limit their application in high-end transducer applications. In this work, a 0.96K0.48Na0.52Nb0.96Sb0.04O3-0.04(Bi0.5-xSmx)Na0.5ZrO3 (abbreviated as T-NKN-xSm) ceramic was designed through phase regulation and texture engineering, which is expected to solve this difficulty. Through our research, we successfully demonstrated the enhanced electromechanical performance of lead-free textured ceramics with a highly oriented [001]c orientation. Notably, the T-NKN-xSm textured ceramics doped with 0.05 mol % Sm exhibited the optimal electromechanical performance: piezoelectric coefficient d33 ≈ 710 pC N-1, longitudinal electromechanical coupling k33 ≈ 0.88, planar electromechanical coupling kp ≈ 0.80, and Curie temperature Tc ≈ 244 °C. Finally, we conducted a detailed investigation into the phase and domain structures of the T-NKN-Sm ceramics, providing valuable insights for achieving high electromechanical properties in NKN-based ceramics. This research serves as a crucial reference for the development of advanced electromechanical devices by facilitating the utilization of lead-free piezoelectric materials with superior performance and environmental benefits.

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.

The unexpected diffuse phase transition in relaxor-PbTiO3 ferroelectrics via acceptor modification

The diffuse phase transition (DPT) and domain structure are essential to the functional properties of relaxor ferroelectrics and are extremely sensitive to the ion doping. The utilization of acceptor doping has been observed to be an effective method in enhancing the high-power properties of relaxor ferroelectric materials. The present study aims to examine the acceptor-doped DPT and domain structure in single crystals of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3. An unexpected physical phenomenon was identified in which Mn-doping increased dielectric diffusion and lowered domain size while suppressing dielectric relaxation. Traceability investigations suggest that Mn-doping inhibited the growth of polar nanoregions by enhancing random electric fields, which increases dielectric diffusion while decreasing the domain size. Meanwhile, Mn doping redistributes the relaxation time function, which results in a reduction in dielectric relaxation. The current research deepens the understanding of the physical basis of DPT and can be applied to the development of high-performance piezoelectric materials.