High-precision Actuators Research Articles

Low-temperature sintering BCZT-Dy ceramics with low strain hysteresis for actuator application

Ba(Cu0.5W0.5)O3 (BCuW)-doped [(Ba0.85Ca0.15)1-xDyx](Zr0.1Ti0.9)O3 (BCZT-xDy, x = 0.001, 0.03) ceramics were prepared by conventional ceramic processing via low-temperature sintering technique. Rather pure perovskite structure and densified morphology with irregular nearly spherical-shape grains are achieved in all ceramics due to liquid-phase sintering. All BCuW-doped BCZT-xDy ceramics present apparent dielectric frequency dispersion and relaxor ferroelectric characteristic due to ion substitution and adding BCuW. The ceramics prepared at optimized sintering temperatures have rather large strain and small strain hysteresis, showing prospect application in piezoelectric high-precision actuators.

An asynchronous dual-foot inertial piezoelectric actuator with strong magnetic compatibility

To address the limitations in actuator selection within strong magnetic environments, this study introduces a novel inertial piezoelectric actuator with asynchronous dual-foot motion, which meets the need for high-precision actuation in strong magnetic field environments. The design principle is to use two driving feet that generate elliptical motion in an alternating method to achieve continuous linear motion of the actuator. This approach enhances load capacity, speed, and stepping characteristics. The design allows for better control of backward motion without modifying the driving waveform, thus improving the actuator's speed and ensuring consistent performance in both directions. A finite element model of the proposed actuator stator is developed and analyzed using commercial software to optimize its dimensional parameters. A prototype is fabricated, and experimental investigations are carried out. The results indicate that the dual asynchronous driving method significantly increases the speed of the actuator and the consistency of the motion by improving stepping characteristics. The prototype reached a maximum speed of 8.98 mm/s, supported a maximum load of 4.5 N, and achieved a displacement resolution of 19 nm. Finally, the strong magnetic field environmental test and MRI image quality test were conducted, and experimental results confirmed that the actuator has superior magnetic compatibility, highlighting its potential for precision applications in challenging environments. This research proposes new methods to enhance the retraction characteristics and output performance of inertial actuators, with their excellent magnetic field compatibility anticipated to be applied in future MRI-compatible injectors, puncture devices, or other actuating mechanisms.

Fabrication of Textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 Electrostrictive Ceramics by Templated Grain Growth Using NaNbO3 Templates and Characterization of Their Electrical Properties

Electrostrictive materials based on (Na0.5Bi0.5)TiO3 are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3, by using templated grain growth. Textured ceramics were prepared with 1~9 wt% NaNbO3 templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 °C for 12 h. Polarization and strain hysteresis loops confirmed the ergodic nature of the system at room temperature, with unipolar strain significantly improving from 0.09% for untextured ceramics to 0.23% post-texturing. A maximum normalized strain, Smax/Emax (d33*), of 581 pm/V was achieved at an electric field of 4 kV/mm for textured ceramics. Textured ceramics also showed enhanced performance over untextured ceramics at lower electric fields. The electrostrictive coefficient Q33 increased from 0.017 m4C−2 for untextured ceramics to 0.043 m4C−2 for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 composition suitable for high-precision actuation applications. Dielectric properties measured between −193 °C and 550 °C distinguished the depolarization, Curie–Weiss and Burns temperatures, and activation energies for polar nanoregion transitions and dc conduction. Dispersive dielectric constants were found to observe the “two” law exhibiting a temperature dependence double the value of the Curie–Weiss constant, with shifts of about 10 °C per frequency decade where the non-dispersive THz limit was identified.

Lead-free ferroelectrics with giant unipolar strain for high-precision actuators

The trade-off between electrostrain and strain hysteresis for piezo/ferroelectric materials largely restrains the development of high precision actuators and remains unresolved over the past few decades. Here, a simple composition of (Bi0.5Na0.5)1-x/100Srx/100TiO3 in the ergodic relaxor state is collaboratively designed through the segregated domain structure with the ferroelectric core, local polarization heterogeneity, and defect engineering. The ferroelectric core can act as a seed to facilitate the field-induced nonpolar-to-polar transition. Together with the internal bias field caused by defect dipoles and adjusted through electric field cycling and heat treatment technology, a giant unipolar strain of 1.03% is achieved in the x = 30 ceramic with a low hysteresis of 27%, while the electric-field-independent large-signal piezoelectric strain coefficient of ~1000 pm/V and ultralow hysteresis of <10% can be obtained in the x = 35 ceramic. Intriguingly, the low-hysteresis high strain also exhibits near-zero remnant strain, excellent temperature and cycling stability.

3D meshless modeling of piezoelectric structure based on the radial point interpolation method

Piezoelectric materials find widespread applications in high-precision actuators and sensors. However, the traditional finite element method falls short in meeting the simulation needs of piezoelectric structures due to complexities in mesh generation and precision requirements for accurate simulations. This paper focuses on adapting and generalizing the meshless modeling technique based on the radial point interpolation method to address three-dimensional simulations of piezoelectric structures and accurately model positive and inverse piezoelectric behaviors. The piezoelectric body is discretized into point cloud data, and displacement and potential are approximated by interpolating values through the radial point interpolation method. Subsequently, a 3D meshless model for general piezoelectric structures is formulated based on the principle of minimum potential energy. The influences of key factors on interpolation accuracy and computational cost were discussed. Numerical examples, featuring a 3D piezoelectric bimorph beam as actuators and sensors, validate the efficacy of this extended approach. Results affirm that the three-dimensional meshless method, rooted in the radial point interpolation technique, achieves superior accuracy in predicting piezoelectric behavior compared to the traditional finite element method. This adaptation not only enhances the applicability of meshless modeling but also represents a significant advancement in accurately simulating complex three-dimensional piezoelectric structures.

Ultrahigh electrostrictive strain and its response to mechanical loading in Nd-doped PMN-PT ceramics

Electrostrictive materials play an important role in the development of high precision actuators, due to the advantages of high resolution, low power dissipation and fast response time. However, the practical application of electrostrictive materials has been hindered by their limited displacement output. To address this, we conducted a study where we doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics with Nd2O3, aiming to significantly improve the electrostrictive effect by enhancing local structural heterogeneities that disrupt the formation of long-range ordered ferroelectric domains. We obtained an optimized electrostrictive strain of 0.231 % with negligible hysteresis at an electric field of 50 kV/cm in 4 %Nd-doped PMN-PT ceramic, surpassing the performance of state-of-the-art lead-based electrostrictive ceramics. Of particular significance is that a high electrostrictive coefficients M33 = 12.2 × 10−16 m2/V2, together with a high mechanical work density of 0.035 J/cm3 and a low power dissipation of 14 %, was achieved under a mechanical prestress of 50 MPa and an electric field of 10 kV/cm. Additionally, this material exhibits excellent fatigue resistance, with less than 3 % variation over 106 operation cycles. All these findings position 4 %Nd-doped PMN-PT ceramics as a promising candidate for high-performance electromechanical actuator applications.

Low-Friction Soft Robots for Targeted Bacterial Infection Treatment in Gastrointestinal Tract.

Untethered and self-transformable miniature robots are capable of performing reconfigurable deformation and on-demand locomotion, which aid the traversal toward various lumens, and bring revolutionary changes for targeted delivery in gastrointestinal (GI) tract. However, the viscous non-Newtonian liquid environment and plicae gastricae obstacles severely hamper high-precision actuation and payload delivery. Here, we developed a low-friction soft robot by assembly of densely arranged cone structures and grafting of hydrophobic monolayers. The magnetic orientation encoded robot can move in multiple modes, with a substantially reduced drag, terrain adaptability, and improved motion velocity across the non-Newtonian liquids. Notably, the robot stiffness can be reversibly controlled with magnetically induced hardening, enabling on-site scratching and destruction of antibiotic-ineradicable polymeric matrix in biofilms with a low-frequency magnetic field. Furthermore, the magnetocaloric effect can be utilized to eradicate the bacteria by magnetocaloric effect under high-frequency alternating field. To verify the potential applications inside the body, the clinical imaging-guided actuation platforms were developed for vision-based control and delivery of the robots. The developed low-friction robots and clinical imaging-guided actuation platforms show their high potential to perform bacterial infection therapy in various lumens inside the body.

Significantly enhanced reversibility and mechanical stability in grain-oriented MnNiGe-based smart materials

Materials that undergo a magnetostructural transition (MST) usually exhibit fascinating magnetoresponsive properties, making them an important class of smart materials. However, practical application of this class of smart materials has been hindered by structural degradation as well as large irreversibility of the MST during consecutive thermal and field cycles. Here we report a significant improvement of the reversibility and mechanical stability in grain-oriented MnNiGe-based alloys that were fabricated using a directional solidification method. The preferred grain orientation enables synergistic deformations between neighboring grains during the MST, leading to a substantial reduction in the transition-induced stress concentration. As a result, in situ and ex situ microscopic observations demonstrate a good mechanical stability of the textured alloys across the MST, in strong contrast to conventional MM'X (M, M’ = Mn, Fe, Co, Ni; X = Si, Ge) materials with randomly-oriented grains. The detailed transition stages of the MST have also been observed at the microscopic scale, and are reported for the first time in the MM'X family. Besides, a low thermal hysteresis (ΔThys) of ∼ 4 K was obtained in the textured alloys, which is the lowest ΔThys in the MM'X material family. Textured MnNiGe-based alloys show a large reversible isothermal entropy change (≥ 35.9 Jkg−1K−1) in a 5 T field change, which is the highest among typical magnetocaloric materials. Consequently, this work provides a promising strategy for enhancing the cyclic stability of materials with a MST, which may boost their practical applications in solid-state refrigerators, energy harvesters and high-precision actuators.

Ultrahigh Electrostrictive Effect in Lead-Free Ferroelectric Ceramics Via Texture Engineering.

The electrostrictive effect, which induces strain in ferroelectric ceramics, offers distinct advantages over its piezoelectric counterpart for high-precision actuator applications, including anhysteretic behavior even at high frequencies, rapid reaction times, and no requirement for poling. Historically, commercially available electrostrictive materials have been lead oxide-based. However, global restrictions on the use of lead in electronic components necessitate the exploration of lead-free electrostrictive ceramics with a high strain performance. Although various engineering strategies for producing materials with high strain have been proposed, they typically come at the expense of increased strain hysteresis. Here, we describe the extraordinary electrostrictive response of (Ba0.95Ca0.05)(Ti0.88Sn0.12)O3 (BCTS) ceramics with ultrahigh electrostrictive strain and negligible hysteresis achieved through texture engineering leveraging the anisotropic intrinsic lattice contribution. The BCTS ceramics exhibit a high unipolar strain of 0.175%, a substantial electrostrictive coefficient Q33 of 0.0715 m4 C-2, and an ultralow hysteresis of less than 0.8%. Notably, the Q33 value is three times greater than that of high-performance lead-based Pb(Mg1/3Nb2/3)O3 electrostrictive ceramics. Multiscale structural analyses demonstrate that the electrostrictive effect dominates the BCTS strain response. This research introduces a novel approach to texture engineering to enhance the electrostrictive effect, offering a promising paradigm for future advancements in this field.

Thermal and fatigue endurance strain response in low temperature sintered 0.4PZN-0.6PZT ceramics for actuator applications

Piezo-ceramics with low sintering temperature (<1000 °C), enhanced strain (>0.1 %), low degree of hysteresis (<10 %), fatigue resistance (>106 cycles) with better thermal stability are extremely important characteristics for the development of high performance and cost-effective actuators. In this study, temperature (−50 to 250 °C) and fatigue (100 to 106) dependence of ferro/piezoelectric (P-E/S-E) characteristics of low temperature sintered (950 °C) (0.4[Pb(Zn1/3Nb2/3)O3-0.6Pb(Zr0.49Ti0.51)O3]) ceramics was investigated. A thermally stable strain response with a maximum of 0.17 % and degree of strain hysteresis (ηhys) of < 10 % was observed till 250 °C. The fatigue studies revealed a robust unipolar strain stability till 106 cycles even up to 200 °C. Interestingly, a very minimal strain asymmetry (γS) was observed only after 104 cycles till 200 °C, unlike PZT-5A, PIC151 and PMN-PT. This study demonstrates an exceptional thermal and fatigue resistant strain response even close to the Curie transition temperature (TC ∼ 280 °C) and suggests that the low temperature sintered 0.4PZN-0.6PZT ceramics could be a promising material, exclusively for high-precision actuator applications over a wide temperature range with a cost-effective solution.

Engineered colossal linear thermal expansion in nanocrystalline NiTi micropillars by stress

Materials with unusual large negative and positive thermal expansions are attractive for applications in high-precision actuation and thermal expansion compensation. So far, such unusual property has been reported in a variety of framework materials and polymers but it remains challenging to obtain in metals. Here, we report a colossal linear thermal expansion in single-phase nanocrystalline NiTi ferroelastic alloy under uniaxial compressive stress. By microscale isothermal severe plastic deformation, we fabricated fully austenitic and martensitic NiTi nanocrystalline micropillars that respectively possess high yield stresses of 2.65 GPa and 2.23 GPa and strong negative, and positive temperature dependence of Young′s modulus (dE/dT). We demonstrate that due to the large dE/dT, the coefficient of linear thermal expansion (CTE) of the austenitic and martensitic NiTi micropillars can be tailored to values of +106×10−6 K–1 and -88×10−6 K–1 by applying 2.5 GPa and 2.0 GPa compressive stress. Such tailored CTEs are approximately 10 times larger than the typical value (∼10×10−6 K–1) of metallic materials. Our work provides a mechanical route to obtain colossal positive and negative thermal expansion in single-phase nanostructured ferroelastic alloys at microscale.

Ultrahigh electrostrictive coefficient and hysteresis-free electrostrictive strain in textured BCZT ceramic

Precision-controlled systems necessitate electronic actuators with large displacement, high precision, and miniaturization. Therefore, advanced ferroelectric functional ceramic materials must exhibit substantial displacement responsiveness, minimal hysteresis, and performance stability. Modifying electrostrictive ceramics to enhance the electrostrictive coefficient (Q33) through conventional doping strategies has proven challenging. To address this, grain-oriented textured ceramics harness crystalline anisotropy to elevate Q33 and electrostrictive strain response. In this work, we employ the template grain growth (TGG) method integrating preprepared BaTiO3 (BT) microtemplates, to cultivate <001>-oriented 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT) ceramics. Remarkably, the <001>-oriented BCZT ceramic manifests a substantial Q33 value of 0.066 m4/C2, marking a 65 % increase compared to randomly oriented ceramics. Under 100 kV/cm, ultra-high electrostrictive strain response (0.23%) and minimal hysteresis (1−8%) were achieved. Crucially, this elevated Q33 remains thermally stable within the range of 20−100 °C. This advancement not only enables the production of electrostrictive ceramics with improved Q33 and hysteresis-free strain but also broadens the application horizon of BCZT-based electrostrictive ceramics within high-precision actuator technologies.

Optimized Strain Response in (Co0.5Nb0.5)4+-Doped 76Bi0.5Na0.5TiO3-24SrTiO3 Relaxors

High strain with low hysteresis is crucial for commercial applications in high precision actuators. However, the clear conflict between the high strain and low hysteresis in BNT-based ceramics has long been an obstacle to actual precise actuating or positioning applications. To obtain piezoceramics with high strain and low hysteresis, it is necessary to enhance the electrostrictive effect and develop an ergodic relaxor (ER) and nonergodic relaxor (NR) phase boundary under ambient conditions. In this work, (Co0.5Nb0.5)4+ doped 76Bi0.5Na0.5TiO3-24SrTiO3 (BNST24) relaxors were fabricated using the conventional solid state reaction route. X-ray diffraction patterns revealed the B-site substitution in BNST24 ceramics. By adjusting the (Co0.5Nb0.5)4+ doping in BNST24, we effectively tuned the TNR-ER and Td close to ambient temperature, which contributed to the development of the ergodic relaxor phase and enhanced the electrostrictive effect at ambient temperature. The I-P-E loops and bipolar strain curves verified the gradual evolution from NR to ER states, while the enhanced electrostrictive effect was verified by the nearly linear S-P2 curves and improved electrostrictive coefficient of the BNST24-xCN relaxors. An enhanced strain of 0.34% (d*33 = 483 pm/V) with low hysteresis of 8.9% was simultaneously achieved in the BNST24-0.02CN relaxors. The enhanced strain was mainly attributed to the proximity effect at the ER and NR phase boundary of BNST24-0.02CN, while the improved electrostrictive effect contributed to the reduced strain hysteresis. Our work demonstrates an effective strategy for balancing the paradox of high strain and low hysteresis in piezoceramics.

Development and Prospect of Smart Materials and Structures for Aerospace Sensing Systems and Applications.

The rapid development of the aviation industry has put forward higher and higher requirements for material properties, and the research on smart material structure has also received widespread attention. Smart materials (e.g., piezoelectric materials, shape memory materials, and giant magnetostrictive materials) have unique physical properties and excellent integration properties, and they perform well as sensors or actuators in the aviation industry, providing a solid material foundation for various intelligent applications in the aviation industry. As a popular smart material, piezoelectric materials have a large number of application research in structural health monitoring, energy harvest, vibration and noise control, damage control, and other fields. As a unique material with deformation ability, shape memory materials have their own outstanding performance in the field of shape control, low-shock release, vibration control, and impact absorption. At the same time, as a material to assist other structures, it also has important applications in the fields of sealing connection and structural self-healing. Giant magnetostrictive material is a representative advanced material, which has unique application advantages in guided wave monitoring, vibration control, energy harvest, and other directions. In addition, giant magnetostrictive materials themselves have high-resolution output, and there are many studies in the direction of high-precision actuators. Some smart materials are summarized and discussed in the above application directions, aiming at providing a reference for the initial development of follow-up related research.

Polarity Modulation Induced High Electrostrain Performance with Near-Zero Hysteresis in a (Sr0.7Bi0.2□0.1)TiO3-Based System

High-precision piezo actuators necessitate dielectrics with high electrostrain performance with low hysteresis. Polarity-modulated (Sr0.7Bi0.2□0.1)TiO3-based ceramics exhibit extraordinarily discrete multiphase coexistence regions: (i) the relaxor phase coexistence (RPC) region with local weakly polar tetragonal (T) and pseudocubic (Pc) short-range polar nanodomains and (ii) the ferroelectric phase coexistence (FPC) region with T long-range domains and Pc nanodomains. The RPC composition features a specially high and pure electrostrain performance with near-zero hysteresis (S ∼ 0.185%, Q33 ∼ 0.038 m4·C-2), which is double those of conventional Pb(Mg1/3Nb2/3)O3-based ceramics. Particular interest is paid to the RPC and FPC with multiscale characterization to unravel local structure-performance relationships. Guided by piezoelectric force microscopy, scanning transmission electron microscopy, and phase-field simulations, the RPC composition with multiphase low-angle weakly polar nanodomains shows local structural heterogeneity and contributes to a flat local free energy profile and thus to nanodomain switching and superior electrostrain performance, in contrast to the FPC composition with a macroscopic domain that shows stark hysteresis. This work provides a paradigm to design high-precision actuator materials with large electrostrain and ultralow hysteresis, extending our knowledge of multiphase coexistence species in ferroelectrics.

Temperature-insensitive strain response in Bi(Zn1/2Ti1/2)O3–PbZrO3–PbTiO3 ferroelectric ceramics simultaneously with low hysteresis for high-precision actuators application

Temperature stability and strain hysteresis are two extremely important parameters for high-precision piezoelectric actuators applications. Piezoelectric ceramics with high temperature stability and low strain hysteresis are eagerly expected. In this work, the strain characteristics of xBi(Zn1/2Ti1/2)O3-(1-x)(0.55PbZrO3-0.45PbTiO3) [xBZT-(1-x)(PZ-PT)] ferroelectric ceramics were investigated meticulously, and temperature-insensitive strain response and low strain hysteresis were simultaneously acquired at x = 0.15. The strain variation was less than 10% in the temperature range of 30–100 °C and the strain hysteresis was only 6% at 7 kV/mm. The incorporation of BZT transforms the crystal structure of PZ-PT ceramics from morphotropic phase boundary (MPB) to tetragonal phase. Strong relaxation behaviors occurred and a large piezoelectric coefficient of 500 p.m./V at 2 kV/mm were obtained at x = 0.15. The above merits will make this ferroelectric ceramic an ideal material for the fabrication of high-precision actuators and their use in harsh environment conditions.

Giant energy storage efficiency and low strain hysteresis in lead-free relaxor ferroelectrics by designing the dynamic behavior of PNRs

Lead-free ferroelectric ceramics have aroused widespread concerns, due to their properties of rapid charge/discharge and electric-induced strain without harming the environment. However, compared with thin-film capacitors, ceramics have a larger energy loss. In addition, the large time lag between electric field and strain also reduces its accuracy as an actuator. Therefore, the relaxor ternary solid solution (BaTiO3–Bi0.48Na0.48La0.03TiO3–NaNbO3) was constructed in this work, aiming to obtain large energy storage efficiency and low time delay. The strategy and optimization aim to improve the relaxation degree and reduce the maximum permittivity temperature to room temperature, building a special crossover region where high and low dynamic polar nano regions co-existence. Thus a recoverable energy density of 1.24 J/cm3 under a low electric field (135 kV/cm) and a high energy storage efficiency (96%) are obtained and low hysteresis electrostriction with a large electrostriction coefficient (Q33 = 0.0367 m4/C2) is also achieved in this system. This work suggests that this system can be considered promising materials as high-efficiency capacitors and high-precision actuators. It also attracts interest in the basic research on the dynamic changes of polar nano regions.

Giant electrostrictive coefficient of KNN-based lead-free ferroelectrics

The development of (K, Na)NbO3 (KNN)-based lead-free materials with excellent piezoelectric properties has become an vital aspects in recent years, based on the environmental friendliness and potential for device. As the typical electromechanical property, the electrostrictive effect is tightly linked to piezoelectric response, which is dominating the market of high-precision actuators. However, the electrostriction behaviors of KNN-based piezoelectric materials have been little studied as yet, evoking the exploration for the electrostrictive effect potential urgently. Here, a typical KNN-based piezoelectric material of (1-x)K0.5Na0.5NbO3-xBi0.5Na0.5ZrO3 (KNN-xBNZ, x = 0.09, 0.10, 0.11) has been concentrated on the enhanced relaxor characteristic due to destroyed ferroelectric long-range orders via introducing high content of BNZ, aiming to strengthen the electrostriction. A giant electrostrictive coefficient (Q33 ∼ 0.067 m4/C2) is achieved in KNN-0.1BNZ materials, nearly three times higher than that of reported Pb(Zr, Ti)O3-based materials, and comparable to some typical BaTiO3-based materials. The optimization of Q33 roots in the co-doped appropriate of Bi3+ and Zr4+ at A or B site, which induces the heterogeneous structure and then limits the range of movement for ions on B site. Significantly, a pretty frequency stability of the remarkable Q33 (>0.054 m4/C2 under the frequency of 1–100 Hz) is revealed, benefiting to application for some commercial fuel injectors’ actuators. This research provides a high-performance electrostrictive material, promoting the research of eco-friendly piezoelectric materials.

Large strain and reduced hysteresis of BiFeO3-xBaTiO3 lead-free ceramic via multiphase coexistence and relaxor behaviors

Ferroelectric ceramics with large strain response, low hysteresis and high Curie temperature (TC) are required for contemporary displacement actuator. In this work, (1-x)BiFeO3-xBaTiO3 ceramics were synthesized using traditional solid sintering technique. A high electric field-induced strain (0.25%), a relatively low hysteresis (22.5%) and a high Curie temperature (415 °C) were achieved in BiFeO3-0.35BaTiO3 ceramic. Meanwhile, the ceramics exhibited apparent relaxor behavior owing to the local structural heterogeneity. Aberration-corrected scanning transmission electron microscopy revealed that polar nano-regions with multiphase coexistence occur in the material, which is the microstructure origin of the enhanced strain and low hysteresis in BiFeO3-0.35BaTiO3 ceramics. This work indicates that BiFeO3–BaTiO3-based ceramics are good high-temperature ferroelectric materials and are promising candidates for high-precision actuator.

Ultra-slim electrostrains with superior temperature-stability in lead-free sodium niobate-based ferroelectric perovskite

Large electrostrains with high temperature stability and low hysteresis are essential for applications in high-precision actuator devices. However, achieving simultaneously all three of the aforementioned features in ferroelectric ceramics remains a considerable challenge. In this work, we firstly report a high unipolar electrostrain (0.12% at 60 kV/cm) in (1–x)NaNbO3-x[(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3] (NN-xBCZT) ferroelectric polycrystalline ceramics with excellent thermal stability (variation less than 10% in the temperature range of 30–160 °C) and ultra-low hysteresis (<6%). Secondly, the high-field electrostrain response is dominated by the intrinsic electrostrictive effect, which may account for more than 80% of the electrostrain. Furthermore, due to the thermal stability of the polarization in the pure tetragonal phase, the large electrostrain demonstrates extraordinarily high stability from room temperature to 140 °C. Finally, in-situ piezoelectric force microscopy reveals ultra-highly stable domain structures, which also guarantee the thermal stability of the electrostrain in (NN-xBCZT ferroelectrics ceramics. This study not only clarifies the origin of thermally stable electrostrain in NN-xBCZT ferroelectric perovskite in terms of electrostrictive effect, but also provides ideas for developing applicable ferroelectric ceramic materials used in actuator devices with excellent thermal stability.