Electrostrictive Ceramics Research Articles

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.

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.

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.

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.

Data-driven methods for discovery of next-generation electrostrictive materials

AbstractAll dielectrics exhibit electrostriction, i.e., display a quadratic strain response to an electric field compared to the linear strain dependence of piezoelectrics. As such, there is significant interest in discovering new electrostrictors with enhanced electrostrictive coefficients, especially as electrostrictors can exhibit effective piezoelectricity when a bias electric field is applied. We present the results of a study combining data mining and first-principles computations that indicate that there exists a group of iodides, bromides, and chlorides that have electrostrictive coefficients exceeding 10 m4 C–2 which are substantially higher than typical oxide electrostrictive ceramics and polymers. The corresponding effective piezoelectric voltage coefficients are three orders of magnitude larger than lead zirconate titanate.

Large Non-Classical Electrostriction in Aliovalent and Isovalent Doped Ceria

The majority of commonly used electrostrictive ceramics are based on lead manganese niobate. These ceramics display large electrostriction strain coefficients ≈ 10-16 m2/V2 at frequencies up to a few kHz. However, they suffer from major drawbacks: they require high driving currents (dielectric constant >10000), contain toxic elements, and are incompatible with thin film Si-microfabrication techniques.We have recently reported that ceria ceramics doped with aliovalent cations having crystal radii smaller than that of cerium, display increased high frequency (f >100Hz) longitudinal electrostriction strain coefficients |M|. For instance, with 10 mol% Lu3+ or Yb3+ lanthanide dopants, |M| ~ 10-17 m2/V2 is observed for f >100Hz . Despite Yceria ~200GPa and eceria ~ , these electrostriction strain coefficients are 100-fold larger than estimated on the basis of Newnham’s scaling law for “classical” electrostrictors. Such “non-classical” behavior has been attributed to the formation of highly polarizable, elastic dipoles reorienting under external electric field.Surprisingly, doping with small isovalent dopants, such as Zr and Hf , produces an increase in |M| to , independent of frequency up to several kHz, as determined by converse electrostriction measurements. The introduction of Zr raises the dielectric constant more than predicted by the Clausius-Mossotti relation. This suggests that the presence of a small dopant creates a highly polarizable unit which may be responsible for the large electrostriction strain coefficient. Our results demonstrate that, by systematically adjusting the composition of ceria-based solid solutions, the possibility exists for development of technologically useful electrostrictive materials which are, at the same time, ecologically sound and fully compatible with Si-microfabrication.

High-temperature and long-term stability in Co/Sb-codoped (Bi0.5Na0.5)TiO3-based electrostrictive ceramics

In this study, we report lead-free Co/Sb-codoped (Bi0.5Na0.5)TiO3-based ceramics with enhanced electrostrictive properties and high-temperature and long-term stability. The effect of Co/Sb codoping on the phase structure, electrical properties, and thermal stability of (Bi0.5Na0.5)TiO3-based ceramics was studied. The Co/Sb codoping induced the phase transition from the coexisting rhombohedral (R) − tetragonal (T) phase to the single pseudocubic (Pc) symmetry and the disruption of the long-range ferroelectric order of the ceramics, yielding enhanced electrostrictive properties. A large electrostrictive response was obtained in the sample with 0.02 Co/Sb content, with electrostrictive coefficients Q33 of 0.022–0.024 m4/C2 and electro-strains of 0.35–0.46% under different strengths of the electric field. The electrostrictive material exhibited temperature-insensitive and fatigue-free behavior after up to 105 cycles from room temperature to 120 °C, rendering it a promising material for high-temperature and long-term stability actuator applications.

Femtosecond laser processing of ceria-based micro actuators

In this paper we present a novel femtosecond laser micro-processing of gadolinium doped cerium oxide (CGO) taking advantage of the unique properties of the ultra-short laser pulse. The process can be extended to other materials which are incompatible with conventional deposition/patterning/etching processes. For example, CGO electrostrictive ceramics is lead-free and non-toxic, compatible with Si-microfabrication and exhibits large electrostriction effect at low frequencies. These qualities make CGO into a promising electroactive material for MEMS applications. However, conventional CGO lithography suffers from low yield due to metal shorts and due to damage during the etch and clean processes. Wet patterning of CGO is very difficult and often results in enhanced leakage or shorts between electrodes. These process compatibility issues can be avoided by using laser patterning. As a proof of concept, a precise patterning of electro-active ceramic Ce0.95Gd0.05O1.975 (CGO5) thin films (1.7 μm-thick) by femtosecond laser is demonstrated. The femtosecond laser patterning was used to fabricate double-clamped beam actuators made of CGO5 sandwiched between two metal contacts. The new process is studied and preliminary guide lines are presented. The process design rules are established; for example, a margin between the top contact edges and the CGO layer edges was defined prior to laser ablation to prevent a short-circuiting between top and bottom contacts due to metal ablation. Electro-mechanical testing of the resulting devices demonstrates the long-term mechanical and electrical endurance of 1.2 mm long beams. Using electrical excitation (voltage amplitude of 10 V with a carrier frequency of 10 MHz modulated at 10 Hz), actuation at 10 Hz induced an in-plane strain of 7×10−6 without any observable mechanical degradation for >800 k cycles. The processes presented in this work, therefore, provide a technological framework for integration of CGO into MEMS-devices.

Lead-free Bi(Mg0.5Ti0.5)O3-modified 0.875Bi0.5Na0.5TiO3-0.125BaTiO3 ferroelectric ceramics with tetragonal structure and large field-induced strains

A electrostrictive ceramics were designed by introducing Bi(Mg0.5Ti0.5)O3 into 0.875Bi0.5Na0.5TiO3-0.125BaTiO3 with tetragonal structure. All the specimens prepared by a conventional solid sintering technique exhibit the excellent sintering ability with a high relative density over 97%. It is found that, as BMT added, the specimens undergo a structure crossover from ferroelectric P4mm to ergodic P4bm, and the coexistence of both tetragonal structures takes bridge between them. A large field-induced strain of 0.30% and field-independent strain coefficient of 0.0254 m4/C2 occur at 4 mol.% BMT added. This material with excellent sinterability is suitable for the application in actuators and microposition controllers.

The electrical properties of low-temperature sintered PMN-PT electrostrictive ceramics by LiF modification

LiF was introduced into PMN-PT electrostrictive ceramics as a sintering aid to lower the firing temperature, and its influence on the electrical properties and microstructures were investigated. The sintering temperature was effectively shifted down by the addition of LiF, which could be attributed to the liquid phase sintering mechanism. Dense microstructures with facet grains were found in the modified compositions, where the existence of secondary phase was not detected. The LiF-doped samples showed the decreased T m , causing the enhanced relaxor behavior at room temperature, while the T m increased with the increasing PT content. Excellent electric field-induced strain performance of d (S max /E max ) ~ 526 pm/V (E = 1 kV/mm) with extremely low hysteresis ~3 % of S–E curves was achieved in low-temperature sintered electrostrictive ceramics. This result makes the ceramics much attractive for applications in multilayer-structured actuators.

Optoenergy storage and random walks assisted broadband amplification in Er3+-doped (Pb,La)(Zr,Ti)O3 disordered ceramics

A broadband optical amplification was observed and investigated in Er3+-doped electrostrictive ceramics of lanthanum-modified lead zirconate titanate under a corona atmosphere. The ceramic structure change caused by UV light, electric field, and random walks originated from the diffusive process in intrinsically disordered materials may all contribute to the optical amplification and the associated energy storage. Discussion based on optical energy storage and diffusive equations was given to explain the findings. Those experiments performed made it possible to study random walks and optical amplification in transparent ceramics materials.

Low-temperature sintering of lead-free Bi1/2(Na,K)1/2TiO3-based electrostrictive ceramics with CuO addition

This study investigated low-temperature sintering of (Bi1/2Na1/2)TiO3-based electrostrictive ceramics by employing CuO as a sintering aid. Ceramic specimens with a composition of 0.96Bi1/2-(Na0.82K0.18)1/2TiO3-0.04BaZrO3 were prepared using a conventional solid-state reaction route. Without CuO, specimens required sintering temperatures (T s ) over 1175 °C for sufficient densification while the addition of 0.02-mol CuO in excess decreased the T s down to 1100 °C. A normalized strain, S max /E max , of 363 pm/V was obtained for a CuO-added specimen after sintering at 1100 °C, which was better than that of a high-temperature fired specimen sintered at 1175 °C without CuO (333 pm/V). The CuO-added specimen showed a high electrostrictive constant, Q 33, of 0.023 m4C−2, comparable to that of the Pb(Mg1/3Nb2/3)O3 (PMN) ceramic, which is believed to open a new road for the realization of low cost lead-free ceramic actuators.

Energy harvesting using multilayer structure based on La‐doped PMN‐PT electrostrictive ceramics

AbstractElectrostrictive materials exhibit high induced strain under dc electric fields and this effect is important in generator application. This paper studied the energy‐harvesting performances of La‐doped PMN‐PT electrostrictive ceramics that have rarely been reported. A multilayer structured electrostrictive energy harvester with high dielectric constant and electrostrictive coefficient is proposed. With a strain Sm = 7 × 10−5 (m/m), a peak current value of 630 µA is obtained across a small matched resistance of 450 Ω under a dc electrical field of 1.5 V/µm. The working principle of the device is reviewed and improved to predict the current and power generated by the harvester. Experimental results are compared to the theoretic behaviors of the improved model. A good agreement is observed by the two sets of data. The study on the efficiency of the energy conversion showed that a positive balance between the consumed power and the harvested power was presented by the device. The result demonstrates the potential perspective of the electrostrictive device in energy harvesting applied to low‐power electronics.

Fiber-Optic Electric Field Sensor Based on Electrostriction Effect

This paper presents a new method for measuring AC field strength, with application of electrostriction effect of electrostrictive ceramics and technology of fiber Bragg grating. We use electrostriction effect to design the fiber-optic electric field sensor. This device turns the strain of electrostriction material influenced by electric field into the strain of fiber Bragg grating, then wavelength of feedback changes. We can get the strain of electrostriction material through the comparison between initial wavelength and wavelength of feedback, then measurement of electric field strength can be achieved by detecting the strain of electrostriction material. Experiments indicate that fiber-optic electric field sensor based on electrostriction effect is of effective value for measuring electric field strength, and the response of measuring system to AC electric field is linear. We apply an effective method for the research of measuring electric field strength.

Lead-free electrostrictive bismuth perovskite ceramics with thermally stable field-induced strains

Electric field-induced strain (EFIS) properties of Bi 1/2(Na 0.82K 0.18) 1/2TiO 3 (BNKT) ceramics modified with Sr(K 1/4Nb 3/4)O 3 (SKN) have been investigated as functions of composition and temperature. BNKT ceramics near a phase boundary revealed the coexistence of ferroelectric rhombohedral and tetragonal phases, resulting in a typical ferroelectric butterfly-shaped bipolar S– E loop at room temperature, whose normalized strain ( S max/ E max) showed a significant temperature coefficient of 0.38 pm/V/K. However, 5 mol% SKN-modified BNKT ceramics revealed a typical electrostrictive behaviour with a thermally stable electrostrictive coefficient, Q 33 = 0.021 m 4/C 2, which is almost comparable to that of Pb(Mg 1/3Nb 2/3)O 3 (PMN) ceramics that have been dominantly used as Pb-based electrostrictive materials over the last decades.

Relaxor Ferroelectricity and Electrostrictive Behavior of KNN-ST Ceramics

The new electrostrictive ceramics have been produced from the (1-x) K0.5Na0.5NbO3-xSrTiO3 (KNN-ST, x=0.1-0.25) system by using conventional mixed-oxide methods. Sintering temperatures rise with increasing SrTiO3 content (x=0.1-0.25) and are in a very narrow range. The x-ray diffraction patterns indicate that with the increasing of SrTiO3 up to 0.25, KNN-ST ceramics with a single perovskite structure exhibit a transition from orthorhombic to cubic and no other impure phase appeared. The dielectric and relaxor ferroelectric properties of KNN-ST ceramics are investigated with the different SrTiO3 content. Also, the strain of these ceramics induced by applied electric fields have been studied. The electrostrictive response is similarly as in the classical PMN (lead magnesium niobate), but lower (order of the 10-5) than PMN (order of the 10-3). Furthermore, this system shows translucent, high dielectric constant, thus suggests possible applications in electric-optic devices, electromechanical transducer applications.

Microstructure effect on the properties of electrostrictive Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

We have studied the effect of the mechanical activation of the starting oxide mixture on the particle size of the resulting powders and the microstructure of electrostrictive lead magnesium niobate-lead titanate ceramics. The results demonstrate that reducing the grain size of the ceramics reduces their dielectric permittivity in both weak and strong electric fields, reduces their electrostrictive coefficient M11, shifts the processes related to polarization saturation to higher electric fields, and increases the dielectric and electromechanical hystereses.

DC Bias Field Dependence on High-Power Characteristics of PbTiO3–Pb(Mg1/3Nb2/3)O3 Electrostrictive Ceramics

The mechanical quality factor Qm of a normal ferroelectric ceramic vibrator decreases and heat is given off when the vibrator is continuously driven at a high level of vibration stress under a resonant mode. The irreversible motions of ferroelectric non-180° domain walls in the ferroelectric ceramic vibrator cause this unfavorable behavior. The effect of ferroelectric domain structure under the vibration stress on electromechanical characteristics was studied using relaxor ferroelectric electrostrictive (1-x)PbTiO3–xPb(Mg1/3Nb2/3)O3 (x=1.00, 0.95, 0.90) ceramics. The Qm of the paraelectric Pb(Mg1/3Nb2/3)O3 ceramics was consistently higher than 5000 at a high stress level under a dc bias field. This Qm is much larger than that of typical hard lead zirconate titanate (PZT) ceramics. The Pb(Mg1/3Nb2/3)O3 ceramics show a considerably large piezoelectric d31 constant which is comparable to that of hard PZT ceramics. The electrostrictive ceramics are therefore superior electromechanical vibrator materials for high-power devices.

Effect of Uniaxial Stress Upon the Electromechanical Properties of Various Piezoelectric Ceramics and Single Crystals

A systematic investigation of the stress‐dependent (σ) electromechanical properties of various ferroelectric ceramics and single crystals has been performed. Studies have been carried out on “hard” and “soft” piezoelectrics, electrostrictive ceramics, and various orientations of (1−x)Pb(Mg1/3Nb2/3)O3–(x) PbTiO3 PMN–x%PT single crystals. The large signal piezoelectric constant, acoustic power density, and coupling coefficient have been determined by calculation. The results are compared, in order to develop an understanding of the relative merits of the different types of active acoustic materials.

Vibration-Stress Dependence of Electromechanical Characteristics for Electrostrictive Pb(Mg1/3Nb2/3)O3–Based Ceramics

The mechanical quality factor Qm of a normal ferroelectric, piezoelectric ceramic vibrator decreases and heat is given off, when the vibrator is continuously driven at a high level of vibration-stress under a resonant mode. It has been thought that irreversible motions of ferroelectric non-180° domain walls cause this behavior. The effect of ferroelectric domain structure on the vibration-stress dependence of electromechanical characteristics was studied using relaxor ferroelectric electrostrictive (1-x)PbTiO3-xPb(Mg1/3Nb2/3)O3 (x=1.00, 0.95, 0.90) ceramics. The Qm for the paraelectric crystal phase composition at room temperature is about five times higher than that for hard lead zirconate titanate (PZT) and the decrease of Qm with vibration-stress is suppressed at high stress levels. The piezoelectric d31 constant is almost the same as that of hard PZT. Electrostrictive ceramics are therefore superior electromechanical vibrator materials for high power applications.