Strain Temperature Stability Research Articles

Enhanced Strain Properties and Temperature Stability in Textured Potassium Niobate Sodium-Based Multilayer Piezoelectric Actuators

Enhanced Strain Properties and Temperature Stability in Textured Potassium Niobate Sodium-Based Multilayer Piezoelectric Actuators

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.

Ultra-high strain in Bi0.5(Na0.41K0.09)TiO3 Pb-free piezoelectric ceramics modified by Sr(Hf0.5Sb0.4)O3

The lead-free piezoelectric ceramics used in piezoelectric actuators have attracted extensive attention owing to their substantial electric-field-induced strain. In this study, The (1-x)Bi0.5(Na0.41K0.09)TiO3-xSr(Hf0.5Sb0.4)O3 (BNKT-xSHS) piezoelectric ceramics were synthesized using the conventional solid-state reaction method. The impact of SHS substitution on the microstructure and electrical properties was systematically explored. Among them, the BNKT-0.015SHS sample, featuring ergodic relaxor states, demonstrates a high piezoelectric strain coefficient (d33*) of 785 p.m./V under a low electric field of 50 kV/cm(Strain = 0.392 %). It exhibits a repeatable strain value of 0.47 % under an 80 kV/cm electric field(d33* = 590 p.m./V). Moreover, the strain values remain around 0.4 % between room temperature and 100 °C, with variations within 90 %. The heightened repeatable strain response is considered to be linked to the electric field-induced reversible phase transition occurring within the ergodic relaxor state. The higher strain temperature stability is ascribed to the coexistence of quadrilateral polar nanoregions and rhombic polydomain nanoregions. This study provides an effective example for achieving significant strain responses, presenting a feasible candidate material for applications in piezoelectric actuators.

Excellent strain and temperature stability in PNT-PZT multilayer textured ceramics

A new ceramic system, Pb(Ni1/3Ta2/3)O3-PbZrO3-PbTiO3(PNT-PZT), was found to be able to be textured at low temperatures (≤ 1000 °C) without the addition of sintering aids. Textured 0.24PNT-0.34PZ-0.42PT ceramics with different template contents were successfully prepared at 1000 °C using BaTiO3 platelets as templates. The phase structure, microstructure, electrical properties and strain-temperature stability of the ceramics were studied in detail. The 0.24PNT-0.34PZ-0.42PT-5 vol% BT ceramic has the best comprehensive properties (d33 = 820 pC/N, εr = 2499, EC = 6.25 kV/cm， TC = 180 °C) and excellent temperature stability (strain variation ≤ 5% between 20 °C and 140 °C). Finally, multilayer textured piezoelectric ceramics were prepared and their displacement output characteristics were studied. The multilayer piezoelectric ceramics successfully exhibit excellent strain under small voltage driving. Our work provides a new candidate material for the development of a new generation of multilayer piezoelectric ceramics.

High electric‐field‐induced strain of SnO2‐modified PLSBZT ceramic for actuator applications

AbstractIn this study, piezoelectric and ferroelectric properties of the Pb0.931La0.006Sr0.03Ba0.03(Zr0.535Ti0.465)O3–xwt%SnO2 (PLSBZT–xwt%SnO2) with x = 0–0.6 were investigated comprehensively. When the content of SnO2 was 0.55 wt%, the sample achieved optimum properties obtaining a high Curie temperature (259°C) and a large strain (0.203% at 20 kV/cm). In particular, the sample's maximum strain (Smax) remained stable with a variation of less than 4% between −20 and 120°C. Moreover, the PLSBZT–0.55 wt%SnO2 ceramic not only presented a small εr value of 1662, enabling the actuator to respond quickly, but also had a high value of g33 (35.8 × 10−3 V/m/N). These results implied that SnO2‐modified PLSBZT ceramics have significant potential for actuator applications owing to their high Curie temperature, large electric‐field‐induced strain, fast response, and good strain–temperature stability.

Achieving large strain and excellent temperature stability in PT-PZ-LST piezoelectric ceramics

Lead-based piezoelectric ceramics are the preferred material for commercial piezoelectric ceramic actuators due to their high performance and irreplaceability. However, the operating temperature (<100 °C) and strain (0.1 %∼0.2 %) of lead-based piezoelectric ceramics are still limited. Achieving large strain in a wide temperature range remains challenging. In this paper, a new strategy is proposed to effectively increase the strain value of lead-based piezoelectric ceramics through domain engineering. The new xPbTiO3-(0.97-x)PbZrO3-0.03(La0.1Sr0.80.1)TiO2.95 (xPT-PZ-LST) ternary piezoelectric ceramic system reaches a strain value as high as 0.5 % and exhibits extremely high temperature stability (13 %) in the range of 25–230 °C. By fine-tuning the content of PT components, the average length and width of a typical tetragonal domain are transformed from 800 nm to 80 nm (long and thin) to 300 nm and 200 nm (short and wide), relatively. From the experimental results of PFM and Rayleigh analysis, the high strain can be attributed to the synergistic effect of the reduced coercive field (Ec), enhanced micro-region response, and regulated domain morphology, which ensures that high intrinsic and extrinsic contribution can be achieved at the same time. In this paper, a new strain regulation method is provided for lead-based piezoelectric ceramics, and a valuable large strain material is obtained via domain engineering.

Understanding Crystal Spatial Symmetry of Sm/Mg Heterovalent‐Doped BST–BNT Ceramics: An Effect Mechanism for Electrical Properties

The effect mechanism of lattice distortion caused by heterovalent rare‐earth and alkaline‐earth ions co‐doping in the electrical properties of piezo‐ceramics is generally concerning. Herein, the Sm2O3/MgO co‐doped 0.65(Ba0.96Sr0.04TiO3)–0.35(Bi0.50Na0.50TiO3) (BST–BNT: x(Sm, Mg)) (0 ≤ x ≤ 0.25 wt%) ceramics are prepared by Pechini sol–gel method. The reversibility transition from the tetragonal P4/mmm relaxation paraelectric phase to the tetragonal P4mm relaxation ferroelectric phase confirms the doping‐modulated piezoelectric constants’ response to the spatial symmetry. Excessive Sm3+ and Mg2+ in the interstitial lattice inhibit the Jahn–Teller effect of distortion in the crystal spatial symmetry. The restored P4/mmm spatial symmetry of BST–BNT: x(Sm, Mg) (x = 0.15 wt%) ceramics contributes to the large electric‐induced strain, increased Curie temperature, and the stabilized frequency dependence of the Curie temperature (TC [1 MHz] = 167 °C, εr [1 MHz] = 2151.92, d33 = 43 pC N−1, Smax/Emax = 535.22 pm V−1). The samples with large electric‐induced strain and good temperature stability of electrical properties can be applied in the heat dissipation actuators.

Excellent temperature stability of strain in PZ-PT-BNT ternary ceramics

Lead-based Pb(Zr, Ti)O3 ceramics have been widely applied in piezoelectric actuators, and yet high temperature stability and large strain have been pursued for further application. In this work, a novel PbZrO3–PbTiO3-(Bi0.5Na0.5)TiO3 (PZ-PT-BNT) piezoelectric ceramic is designed and prepared by solid-state route. It is found that the introduction of BNT constituent enhances the relaxation behavior of PZ-PT ceramic, inhibits the abrupt change in dielectric properties near Curie temperature, and increases the proportion of tetragonal phase with high temperature stability. Meanwhile, the patterns of electric domains are intentionally modified by adjusting composition of PZ-PT-BNT. Short and broad electric domains in PZ-PT-0.03BNT ceramic are observed by piezoresponse force microscopy, which are insensitive to temperature and have faster response under electric field, contributing to strain characteristics. As a result, through integrating phase structure and electric domain configuration, a strain of 0.21% and excellent temperature stability where the variation of strain is less than 8% in the temperature range of 25–250 °C are achieved in PZ-PT-0.03BNT ceramic. The findings provide an effective strategy for improving the strain stability of PZ-PT-based piezoelectric ceramics, and demonstrate that PZ-PT-BNT ceramics have potential application prospects in high-temperature piezoelectric actuators.

Giant Electric Field‐Induced Strain with High Temperature‐Stability in Textured KNN‐Based Piezoceramics for Actuator Applications

AbstractLarge‐strain (K,Na)NbO3 (KNN) based piezoceramics are attractive for next‐generation actuators because of growing environmental concerns. However, inferior performance with poor temperature stability greatly hinders their industrialized procedure. Herein, a feasible strategy is proposed by introducing ‐ defect dipoles and constructing grain orientation to enhance the strain performance and temperature stability of KNN‐based piezoceramics. This textured ceramics with 90.3% texture degree exhibit a giant strain (1.35%) and a large converse piezoelectric coefficient d33* (2700 pm V−1), outperforming most lead‐free piezoceramics and even some single crystals. Meanwhile, the strain deviation at high temperature of 100 °C–200 °C is obviously alleviated from 61% to 35% through texture engineering. From the perspective of practical applications, piezo‐actuators are commonly utilized in the form of multilayer. In order to illustrate the applicability on multilayer actuators, a stack‐type actuator consisted of 5 layers of 0.4 mm thick ceramics is fabricated. It can generate large field‐induced displacement (11.6 µm), and the promising potential in precise positioning and optical modulation are further demonstrated. This work provides a textured KNN‐based piezoceramic with temperature‐stable giant strain properties, and facilitates the lead‐free piezoceramic materials in actuator applications.

Simultaneous Realization of Good Piezoelectric and Strain Temperature Stability via the Synergic Contribution from Multilayer Design and Rare Earth Doping

AbstractNiobate‐based lead‐free piezoceramics have attracted wide attention due to their excellent piezoelectric properties. Although the temperature sensitivity of piezoelectricity or strain in one sample has been solved to a certain extent, how to simultaneously improve the temperature stability of both in one sample is still an issue. Herein, by constructing multilayer composite ceramics and doping Ho element, both improved piezoelectric and strain temperature stability (the variations are below 3% under 30–100 °C) are achieved, showing great property advantage compared with previous reports. Different from the compositionally graded composite ceramic design, the Ho doping can not only increase orthorhombic‐tetragonal phase transition temperature (TO‐T) and then create the condition for the formation of successive phase transition, but also stabilize the oriented domain state. Therefore, the excellent temperature stability of both piezoelectricity and strain can be attributed to the multistep phase transition induced by the multilayer design, the fine regulation of TO‐T interval by the optimization of lamination combination, and the stabilized polarization induced by Ho doping. The new strategy for solving both piezoelectric and strain temperature sensitivity can further promote the commercial application of potassium sodium niobate‐based lead‐free piezoelectric ceramics.

The Effect of Nb2O5 Precursor on KNN-Based Ceramics’ Piezoelectricity and Strain Temperature Stability

The performance of potassium sodium niobate ((K, Na) NbO3, KNN)-based lead-free piezoelectric ceramics has significantly improved over the past decade. However, the performance bottlenecks of KNN-based ceramics cannot be ignored. Here, the Nb2O5 precursor is obtained after thermal pretreatment, which can evidently improve the piezoelectric properties and strain temperature stability of KNN-based ceramics. With the help of the Nb2O5 precursor treated at 800 °C, the optimal piezoelectric constant d33 of 303 pC/N, inverse piezoelectric constant d*33 of 378 pm/V, Curie temperature TC of 310 °C and electromechanical coupling factor kp of 42% are obtained, and the value of d33 improves by about 30% compared with that of the ceramic prepared with untreated Nb2O5 as raw material. Additionally, in comparison with the strain temperature stability of the ceramics prepared with untreated Nb2O5 as raw material, the temperature stability is enhanced. Therefore, this study provides a useful approach to break the existing performance bottleneck and further improve the properties of KNN-based ceramics.

Simultaneously improving piezoelectric strain and temperature stability of KNN‐based ceramics via defect design

Piezoelectric strain and its temperature stability of KNN-based ceramics sintered in reducing atmosphere are improved simultaneously via defects design of Mn doping. MnO and MnO2 as raw materials have an impact on defects in KNN-based ceramics. When the dopant changes from MnO to MnO2, the defects (MnNb′′′, MnK·, MnNa·) concentration decrease and defects (MnNb′) increase. Defect dipoles (MnK·-VK′, MnNa·-VNa′, MnNb′′′-Vo··) in poled and aged 0.94 K0.48Na0.52Nb0.96Ta0.04O3-0.06BaZrO3 + 0.08MnO ceramics form a strong restoring force for domain switching, which enhances the reversibility of the non-180° domains switching and then significantly improves piezoelectric strain. The stable defect dipoles (MnK·-VK′, MnNa·-VNa′) form so that the reversibility of the non-180° domains switching can be preserved to high temperature. This defect dipoles design provides a general method to achieve large piezoelectric strain (582 pm/V@20 kV/cm) and excellent temperature stability (T90 =210 °C).

High-performance BF-BT-based lead-free piezoceramics with local polar nanoregions of room-temperature ergodic state

The present work highlights the successful fabrication of the (1-x)(BF-BHT)-xLST lead-free piezoelectric ceramics by the conventional solid-state method. The composition (x = 0.03) was found with a high Curie temperature of Tc ~ 435 °C and a superior electric field-induced strain as high as 0.42 %. The piezoelectric force microscopy (PFM) and transmission electron microscopy (TEM) measurement revealed the existence of polar nano-regions (PNRs) due to the local compositional heterogeneity which is attributed to the introduced relaxor (La0.1Sr0.8)TiO3-δ. Moreover, the superior temperature stability of piezoelectric strain S*% with the maximum 31 % was obtained in the temperature range of 25–245 °C, indicating that the recipe possesses outstanding high-temperature reliability. The findings in this work provide a novel design philosophy to prepare high-performance BF-BT-based lead-free piezoceramics.

An exploration for new strategy: Achieving both excellent temperature stability and good electrostrain in BiFeO3–BaTiO3-based relaxor ferroelectrics by domain engineering

In BiFeO3-xBaTiO3 (BF-xBT) ceramic systems, some of them exhibit good electrostrain, unfortunately, their electrostrain properties always fluctuate with temperature. To obtain good strain performance with excellent temperature stability, the BiFeO3–BaTiO3-xBi(Mg2/3Nb1/3)O3 (BF-0.4BT-xBMN) relaxor ferroelectrics were designed, and a new strategy of changing the temperature & electric field-dependent characteristics of nanodomains by doping was proposed for the first time. An excellent result (S = 0.27% @80 °C, fluctuating degree≈2% during 80 °C–180 °C) was achieved, much better than previously reported results, presenting great potential in the application of high-temperature devices. Temperature-dependent dielectric permitivity combined with piezo-response force microscopic (PFM) techniques demonstrated that the doping of Bi(Mg2/3Nb1/3)O3 (BMN) decreased the high maximum-dielectric-constant temperature (Tm) and freezing temperature (Tf) as well as the proportion of nanodomains with strong piezo-response. What's more, the temperature-dependent dS/dE curves combined with in-situ synchrotron X-Ray diffraction measurements during electric field loading revealed the transformation from nanodomain into macrodomain (n-m). The introduction of BMN resulted in an increase of the nanodomain-macrodomain transition electric field at room temperature together with the decrease of domain switching at high temperature, both of which were the key to improving the temperature stability of strain.

Effect of stress on the phase transition and optimizing electric-induced strain behavior of Bi0.5Na0.5TiO3-SrTiO3 lead-free co-fired multilayer piezoactuators

A series of (1-x)Bi1/2Na1/2TiO3-xSrTiO3+0.05 wt% MnO2 lead-free multilayer piezoactuators was prepared using a tape casting method, and the field-induced strain performance, temperature stability, electric fatigue and load characteristics were evaluated to assess potential practical applications. In contrast to traditional PZT ceramics, the fabrication of BNT bulk ceramics into multilayer piezoactuators provides significantly decreased strain (S)-electric field (E) characteristics as a result of internal compressive residual stress. The inactive edge distance, sintering temperature and layer thickness were all found to affect the compressive residual stress of the actuator. Through reconstructing the material composition and structure of BNT-ST actuators, active strain (0.168 %, 2 kV/mm), total strain (>0.15 %, E ≤ 2.5 kV/mm) and blocking stress (42.6 MPa) were realized in BNT-based cofired multilayer actuators, displaying a better performance than commercial PZT actuators. These results indicate that environmental-friendly BNT-based lead-free multilayer piezoactuators are promising candidates with regard to practical applications.

Bi(Mg1/2Zr1/2)O3–PbZrO3–PbTiO3 relaxor ferroelectric ceramics with large and temperature-insensitive electric field-induced strain response

A large strain (0.33% at 5 kV mm−1) and high temperature stability (strain variation less than 8%) were obtained simultaneously in new BMZ-PZ-PT ternary ceramics by the substitution of BMZ for PZ in PZT ceramics.

Tuning the Covalency of A-O Bonds to Improve the Performance of KNN-Based Ceramics with Multiphase Coexistence.

Although a room-temperature multiphase coexistence (MPC) strategy improves the piezoelectric coefficient (d33) of potassium sodium niobate ((K,Na)NbO3, KNN) ceramics, it still suffers from the dependencies on composition and temperature, making it remain challenging to further improve d33 and temperature stability of strain for an already-built MPC. Here, we proposed a new route to resolve this issue, that is, tuning the covalency of A-O bonds in an already-built MPC. We chose 0.96(Na0.60K0.40)(Nb0.955Sb0.045)O3-0.04(Bi0.5Na0.5)ZrO3 ceramics as an already-built MPC and replaced (Bi0.5Na0.5)2+ with Ba2+ to tune the covalency of A-O bonds. Thus, we synthesized 0.96(Na0.60K0.40)(Nb0.955Sb0.045)O3-0.04(Bi0.5Na0.5)1-xBaxZrO3 ceramics. We not only improved d33 values from 450 pC/N (at x = 0) to 500-505 pC/N (at x = 0.05-0.10) but also obtained the enhanced temperature stability for strain at x = 0.10, outperforming that of samples with x = 0 and other KNN-based ceramics. The increased d33 is attributed to the well-preserved MPC and the repaired long-range ordering, and the improved temperature stability of strain is due to shifting the MPC to a slightly higher temperature than room temperature. Therefore, the new route is useful to further improve the performance of an already-built MPC, benefiting to the future design of MPC and the practical application of KNN-based ceramics.

New Role of Relaxor Multiphase Coexistence in Potassium Sodium Niobate Ceramics: Reduced Electric Field Dependence of Strain Temperature Stability.

The influence of relaxor behavior on strain behavior is less investigated in potassium sodium niobate [(K, Na)NbO3, KNN] ceramics. Here, we report novel phenomena in the temperature-dependent strain behavior with the electric field of KNN-based ceramics with relaxation characteristics. The strain temperature stability is electric field dependent below the threshold electric field: temperature-dependent strain can be effectively improved by increasing the applied electric fields, while it remains almost electric field independent above the threshold electric field. Such a macroscopic property change can be well consistent with the following microscopic domain structure evolution. Little voltage dependence is found above a certain voltage by employing voltage-dependent piezoresponse hysteresis loops and domain switching under different temperatures, implying the contribution of domain behavior to the change of strain. Ergodic polar nanoregions (PNRs) are induced by the high-density domain walls among nanodomains in the relaxor samples, as revealed by the atomic-resolution polarization mapping with Z-contrast. The facilitated domain switching due to the lowered energy barrier and nearly vanished polarization anisotropy based on the PNRs with nanoscale multiphase coexistence can promote the electric field compensation for temperature effect. This work demonstrates the contribution of relaxor behavior to the electric field dependence of strain temperature stability in KNN-based ceramics.

Synergetic Contributions in Phase Boundary Engineering to the Piezoelectricity of Potassium Sodium Niobate Lead-Free Piezoceramics.

Although the pronounced piezoelectricity was obtained in (K, Na)NbO3 piezoceramics with the phase boundary engineering (PBE), the physical mechanisms remain pending. Here, we revealed for the first time how PBE influences the piezoelectric properties through synergetic contributions. Cryogenic experiments confirm that PBE constructs a phase coexistence, consisting of rhombohedral (R), orthorhombic (O), and tetragonal (T) phases, with a structural softening, by which a high piezoelectric coefficient d33 of 555 pC/N and the enhanced temperature stability of strain are achieved. The phenomenological theory and transmission electron microscopy demonstrate that the superior d33 hinges on the flattened Gibbs free energy and the abundant nanodomains (10-80 nm), which induce the enhanced permittivity and the coexisting single domain and multidomain zones, respectively. In particular, we disclosed a trade-off relationship between ferroelectric domains and polar nanoregions (PNRs) and found the "double-edged sword" role of PNRs in the piezoelectricity enhancement. Therefore, this work helps understand the physical mechanisms of the piezoelectricity enhancement, benefiting the future research of lead-free piezoceramics.

Coexistence of excellent piezoelectric performance and high Curie temperature in KNN-based lead-free piezoelectric ceramics

A new KNN-based lead-free piezoelectric material system of (1-x)K0.4Na0.6Nb0.96Sb0.04O3-x(Bi0.45Sm0.05)Na0.5ZrO3 (abbreviated as KNNS-xBSNZ, 0.00 ≤ x ≤ 0.06) is designed to obtain high performance to meet the requirement of next generation electronic devices. The relevant electric properties such as piezoelectricity, strain, and temperature stability are analyzed in detail. An excellent comprehensive property (d33∼508 pC/N, TC∼268 °C) is obtained in ceramic with x = 0.04 through the construction of rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary. In addition, a good temperature stability of strain for KNNS-0.04BSNZ ceramic is also obtained within the range from room temperature to 175 °C (Suni100°C/SuniRT∼97.81%, Suni150°C/SuniRT∼84.67%), which is comparatively superior to some reported KNN-based ceramics and lead-based ceramics. Therefore, we believe that this new material system would be a promising lead-free candidate for the practical applications.