High D33 Value Research Articles

Improved piezoelectric properties and thermal stability in ZnO-modified 0.39BiScO3-0.61PbTiO3 ceramics by structure regulation

In this work, ZnO was introduced into 0.39BiScO3-0.61PbTiO3 (xZn-BS-61PT), and the phase structure and local structure of ceramics were controlled by a combination of cation substitution and ceramic/semiconductor composite, so as to improve the piezoelectric properties and temperature stability of ceramics. Zn2+ substitute B-site Ti4+ of BS-61PT, resulting in a stable coexistence of rhombohedral (R)-tetragonal (T)-monoclinic (M) phases dominated by T phase. Excessive Zn ions displace the Sc ions, making Sc ions spontaneously crystallize at grain boundaries in the form of an oxide at x ≥ 0.015. The piezoelectric coefficient and Curie temperature (d33, Tc) are increased from (326 pC/N, 416 °C) for x = 0 to (431 pC/N, 433 °C) for x= 0.015. After annealing at 200 °C, the ZnO-modified samples still retrain high d33 value (d33 > 330 pC/N). For x=0.015 sample, after aged 12 months, the retrained d33 is 395 pC/N, only down 8%. The improved properties are attributed to the synergistic effects of phase structure, point defects and local electric fields. Our results provide a design strategy to simultaneously improve the piezoelectric properties and temperature stability. Meanwhile, it is beneficial to broaden the phase.boundary (MPB) composition range of BS-xPT ceramics, and reduce the dependence of performance on components.

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.

Impact of Gd-doping on structural and electrical properties of 0.4CaBi2Nb2O9-0.6Na0.5Bi2.5Nb2O9 piezoelectric ceramics

This paper focuses on improving the electrical properties of 0.4CaBi2Nb2O9-0.6Na0.5Bi2.5Nb2O9 piezoelectric ceramics through Gd doping. The effect of Gd3+ replacing Ca2+ and Na+ on the 0.4CaBi2Nb2O9-0.6Na0.5Bi2.5Nb2O9 (0.4CBN-0.6NBN) piezoelectric ceramics was subjected to a comprehensive examination. The introduction of Gd3+ has led to the development of a pseudo-tetragonal phase, enhancing the polarization and strengthening the piezoelectric effect. Among the 0.4CBN-0.6NBN-xGd (x = 0.00–0.05) ceramic samples, the sample at x = 0.03 that exhibits the best piezoelectric properties demonstrates a high Curie temperature of 849.7 °C, low dielectric loss (tanδ) of 1.295 % (at 550 °C), high DC resistivity (ρDC) of 1.58 × 108 Ω‧cm (at 500 °C), and a high d33 value of 17.3 pC/N. Following annealing at 800 °C, its d33 retains 94.2 % of its initial value. The improved electrical performances indicate that the Gd-doped 0.4CBN-0.6NBN ceramics hold a great deal of promise for high-temperature piezoelectric applications.

Modification of domain construction in PNN-PIN-PT piezoelectric ceramics for high electromechanical performance using defect engineering

Good piezoelectric properties and low mechanical losses are prerequisites for the application of high-power devices. In this study, an appropriate amount of Mn ions was introduced into a piezoelectric 0.46Pb(Ni1/3Nb2/3)O3-0.23Pb(In1/2Nb1/2)O3-0.31PbTiO3 ceramic to enhance its electromechanical properties. The results revealed that the mechanical quality factor(Qm) value of the ceramic was improved while maintaining high piezoelectric properties, and the dielectric loss was reduced. When Mn doping is 1.0 mol%, the d33 component decreased by only ∼21%, while Qm increased by ∼13 times (d33 = 750 pC/N, Qm = 385, tanδ = 0.66%). The measurement of the internal bias field (Ei) in the P-E loops of aged and nonaged samples showed that aging promoted the directional alignment of defect dipoles and improved their Qm. According to the PFM data, significant increase in Qm was mainly due to the "bulk effect" caused by low domain wall density. In turn, widening and lengthening of domains promoted the accumulation of most defective dipoles in the ceramic body, which greatly amplified the hardening effect. This work provides a good example of enhancing Qm in ceramic systems with high d33 values through the construction of low domain wall densities.

Piezoelectric response and figure of merit assessment in lead-free (Ba1-xSrx)(Zr0·025Ti0.975)O3 ceramics with low-level Sr2+ substitutions

This study investigates the effects of low-level Sr2+ substitutions on the microstructures and electrical properties of BSZT ceramics with formula (Ba1-xSrx)(Zr0·025Ti0.975)O3. The ability of BSZT ceramics to convert energy is assessed based on the piezoelectric coefficient, d33 associated with the figure of merit (FOM). BSZT ceramics with 0.00 ≤ x ≤ 0.10 were sintered at 1350 °C for 2 h. The XRD measurement confirmed the formation of a single-crystalline phase in all ceramics. All ceramics stabilized in tetragonal crystal structures with progressive decline in tetragonality. It was found that the ceramic with low-level Sr2+ substitutions demonstrated excellent dielectric, piezoelectric and ferroelectric behaviours before gradually deteriorated at higher contents. Systematic deviation of Sr2+ atomic percentage signified broad dielectric curves compared to pristine Ba(Zr0·025Ti0.975)O3. A significant increase of remnant polarization, Pr value (11.21 ± 0.12 μC/cm2) was recorded when x = 0.02, in line with its highest as-sintered density and tetragonality. High d33 and low ε33 values contributed to an optimum value of piezoelectric voltage, g33 coefficient. Consequently, a high FOM comparable to PZT was obtained. The current work successfully demonstrated the preparation of lead-free ceramics based on BaTiO3 with great potential for energy conversion applications.

Flash sintering of lead zirconate titanate ceramics under high voltage at room temperature

Flash sintering has been applied to various ceramics since it was first reported. However, the flash sintering of lead zirconate titanate (PZT) at room temperature has not been accomplished. In this study, flash sintering of PZT piezoelectric ceramics at room temperature was realised for the first time. Subsequent to surface treatment in a low-pressure environment, the sample was flash-sintered at a high voltage in air. The sample became dense rapidly during sintering. The results showed that after 300 s of sintering, the flash-sintered samples had a high density (98.1%) and d33 values (273 pC/N). The d33 is the highest compared with flash sintering of PZT through the furnace temperature of several hundred degree Celsius. Owing to the extremely short sintering time and the absence of heating devices, this method can greatly reduce energy consumption and lead to volatilisation, providing a new method for the rapid preparation of piezoelectric ceramics.

Strong piezoelectricity of the nm-thick flexible Hf0.5Zr0.5O2 ferroelectric film

Integrated nanoelectromechanical systems (NEMS) exhibit enormous potential for replacing current microelectromechanical systems in various fields, such as 5G/6G wireless communication, in the future. However, their advancement is impeded by the challenge of achieving nanometer-thick ferroelectric oxide films with a high piezoelectric coefficient of d33. Herein, the nm-thick flexible Hf0.5Zr0.5O2 (HZO) films were deposited on mica substrates, and they exhibited a remnant polarization of ≥ 8.1 μC/cm2 at 25–320 °C and a high d33 value of 37.8 pC/N at 25 °C. After the HZO films with inter-digitated electrodes were fully polarized, the flexible HZO film with a dynamic bending strain of 0.102 % at 4 Hz produced an open-circuit voltage of 1.1 V. This HZO film with strong piezoelectricity can promote the development of novel NEMS and flexible piezoelectric sensors.

Grain Boundary Diffusion Hardening in Potassium Sodium Niobate‐Based Ceramics with Full Gradient Composition and High Piezoelectricity

AbstractReducing mechanical losses and suppressing self‐heating are critical characteristics for high‐power piezoelectric applications. For environmentally friendly Pb‐free piezoelectric ceramics, traditional acceptor doping or annealing treatments have successfully improved the mechanical quality factor (Qm) based on a ceramic matrix with a poor piezoelectric coefficient (d33<100 pC/N). Nevertheless, a ceramic with high Qm and d33 values has not been reported owing to the inverse relationship between Qm and d33. Herein, a novel hardening method called grain boundary diffusion is used to develop Pb‐free potassium sodium niobate ceramics, where Qm increased by more than two‐fold (from 51 to 132) and a high d33 value (d33 = 360 pC/N) is maintained. Significantly, d33 retained 98% of its initial value after 180 days, exhibiting improved aging stability. The established properties are associated with the formation of the core‐shell microstructure and the full gradient composition distribution using structural characterizations and phase‐field simulations, where the core maintains a high d33 and the shell provides a hardening effect. The novel hardening effect in piezoelectric materials, known as grain boundary diffusion hardening, highlights the enhancement of the mechanical quality factor with high piezoelectricity, providing a new paradigm for the design of functional materials.

Local piezoelectric properties of Bi3TaTiO9 thin films: The role of grain crystallinity

We report the relationship between grain shape and local piezoelectric coefficient (d33) hysteresis loops in a Bi-layered perovskite Bi3TaTiO9 (BTTO) thin film, fabricated via pulsed laser deposition. The BTTO thin film, deposited on a single-crystal Nb-doped SrTiO3 substrate, exhibited a polycrystalline structure with both elongated and round grains identified through atomic force microscopy. Local d33 hysteresis loops measurements in the BTTO thin film revealed that elongated grains exhibited higher d33 value compared to round grains. Intriguingly, the highest d33 value was measured at the areas where elongated and round grains are adjacent. These findings suggest that piezoelectricity is enhanced when a- and c-oriented crystallinity are present simultaneously in Bi-layered perovskite thin films. This observation parallels the phenomenon of phase coexistence observed near the morphotropic phase boundary in systems such as lead zirconate titanate.

Improving the performance of flexible composites based on 3-3 interconnected skeletons for piezoelectric energy harvesting

With the rapid development of microelectronics and portable devices, flexible piezoelectric electricity generators (FPEGs) as self-powered devices have attracted extensive attention. Piezoelectric ceramic-polymer composites with good flexibility is the core component of FPEGs. Having high d33 and g33 values is also essential for power generation. Herein, the porous ceramic skeleton is prepared using PZT based as the ceramic powder and polyurethane sponge as the template, followed by compounding the porous ceramic skeleton with polydimethylsiloxane (PDMS) by vacuum impregnation to prepare a 3-3 interconnected composite. When the ratio of ceramic phase in the ceramic slurry is 75 wt%, the volume fraction of the ceramic phase in the composite can achieve 37 vol%. Before compounding PDMS, porous ceramics are polarised, which is called pre-polarisation. The d33 value of the pre-polarised composites can reach 158 pC/N as compared to not polarising the porous ceramic and then polarising it after composite; the improvement is 48%. In addition, the g33 value of the pre-polarized composites is up to 144 mV m/N. Moreover, the 3.0 × 1.2 × 0.2 cm3 FPEG can generate a maximum output voltage of 15 V and a maximum short circuit current of 167 nA at 9% compression strain. The maximum instantaneous power density is 990 nW/cm2, thereby providing a new idea for piezoelectric power generation.

Development of PZN-PMN-PZT Piezoelectric Ceramics with High d33 and Qm Values.

To achieve good long-term temperature stability in devices used in energy-conversion applications, this study is aimed at developing combined ceramics, referred to as PZN-PMN-PZT, comprising Pb(Zn1/3Nb2/3)O3 (PZN) and Pb(Mn1/3Nb2/3)O3 (PMN), which are typical relaxor ferroelectric materials, and Pb(Zr,Ti)O3 (PZT). The piezoelectric properties were compared based on several parameters according to the change in the composition ratio between relaxor materials, amounts of Sb2O3 dopant, and Zr/Ti ratio in the PZT system. Finally, we established optimal poling conditions to improve the electrical properties of the optimized piezoelectric material, based on the evaluation of ceramic properties according to the applied voltage during the poling process. The optimized composition of the investigated piezoelectric ceramics is represented by 0.14PZN-0.06PMN-0.80PbZr0.49Ti0.51 + 0.3 wt.% CuO + 0.3 wt.% Fe2O3 with 0.1 wt.% Sb2O3 doping, which yielded the superior properties (d33 = 361 pC/N, Qm = 1234, Tc = 306 °C).

Poling Effects of Piezoelectric Properties of Modified BCZT Ceramics with High Piezoelectric Performance

Due to the toxic of lead content ceramics, many free piezoelectric ceramics have received much attention. To obtain high piezoelectric properties for such free piezoelectric ceramics, poling conditions are often referred. In the present work, effects of the poling electric field on the many properties of Sm doped BCZT ceramic were investigated. The samples were fabricated using a solid-state reaction technique. The XRD analysis indicated that the sample contained a mixture of phases of rhombohedral, tetragonal, and orthorhombic phases with high purity, dense, and large average grain size. A transformation from the symmetric S-E loop for the unpoled sample to an asymmetry loop for the poled sample was observed, while a slight change in the P-E shape was noted. The poling electric field showed a small effect on ɛr and kp values. However, it had large effects on HS, d33, g33, and FoM values. The low HS (9.2%), but high d33 (562 pC/N), g33 (15.55×10−3 Vm/N) and FoM (20.65 pm2/N) values indicated that this ceramic system has potential for piezoelectric and energy harvesting applications.

A Rotary-Linear Ultrasonic Motor Using MnO2-Doped (Ba0.97Ca0.03)(Ti0.96Sn0.005Hf0.035)O3 Lead-Free Piezoelectric Ceramics with Improved Curie Temperature and Temperature Stability

In this work, a cylindrical lead-free rotary-linear ultrasonic motor was attached to piezoelectric plates of MnO2-doped (Ba0.97Ca0.03)(Ti0.96Sn0.005Hf0.035)O3 ceramics using the first bending vibration to pull a thread output shaft of the interior of a stator. The effect of the proposed ceramics’ d33 and Qm values are the key factors for ultrasonic motors. Therefore, MnO2-doped (Ba0.97Ca0.03)(Ti0.96Sn0.005Hf0.035)O3 lead-free piezoelectric ceramics with high values of d33 = 230 pC/N, Qm = 340.8 and a good temperature stability of their dielectric and piezoelectric properties are suitable for application to linear piezoelectric motors. The structure of the linear piezoelectric motor was simulated and fabricated by Finite Element Analysis. The characteristics of linear piezoelectric motors were also studied. The output characteristics of the lead-free piezoelectric motor were a left-pull velocity = 3.21 mm/s, a right-pull velocity = 3.39 mm/s, an up-pull velocity = 2.56 mm/s and a force >2 N at 39.09 kHz for an input voltage of approximately 200 Vp-p (peak to peak). These results are comparable to those for a lead-based piezoelectric motor that uses PZT-4 ceramics. The proposed lead-free piezoelectric motors were successfully fabricated and used to pull a 0.5 mL commercial insulin syringe.

Potassium Sodium Niobate-Based Lead-Free High-Frequency Ultrasonic Transducers for Multifunctional Acoustic Tweezers

Ultrasonic transducers may need to operate in direct contact with the human body, especially with the skin or closer to blood vessels. Eco-friendly lead-free materials and devices are therefore being vigorously developed for biosafety considerations. This work presents high-performance potassium sodium niobate [(K,Na)NbO3, KNN]-based lead-free ceramics with composition-driven multiphase coexistence and their application on high-frequency ultrasonic transducers for multifunctional acoustic tweezers. A high piezoelectric constant d33 value of 332 pC/N, a good Curie temperature TC value of 348 °C, and improved in situ temperature stability were obtained in the piezoceramics via the construction multiple phases near room temperature and domain engineering. One to three piezocomposites were further fabricated based on the synthesized ceramics for higher electromechanical coupling properties. Lead-free high-frequency transducers as multifunctional acoustic tweezers for precise and selective manipulation of microparticles were designed and manufactured with a high center frequency of 23.4 MHz and a broad -6 dB bandwidth of 75.4%. Additionally, a stable transducer performance was obtained over a test temperature range of 23-60 °C, indicating good thermal stability in environments with fluctuating temperatures. Research on lead-free high-frequency transducers for ultrasound imaging and precise and selective manipulation of microparticles demonstrates their broad potential in fields such as medical therapy and diagnosis.

Quantum Dot Hybridization of Piezoelectric Polymer Films for Non-Transfer Integration of Flexible Biomechanical Energy Harvesters.

This work presents a low-temperature engineering strategy, from quantum dot (QD) synthesis to fabrication of a hybrid from a homogeneous dispersion to thermal annealing with elaborate use of a small organic molecule dopamine, for achieving a kind of ZnO QD-hybridized piezoelectric polymer film directly integrated into a flexible electrode and a plastic substrate. This strategy is the key for non-transfer assembly of flexible piezoelectric nanogenerators (FPENGs) with both mechanical robustness and high electrical performance via direct lamination. The rational addition of dopamine plays multiple roles of (1) significantly decreasing the size of ZnO particles to a QD level (3.77 nm), (2) formation of a stable and homogeneous dispersion of a ZnO QDs/piezoelectric polyvinylidene fluoride-co-hexafluoropropylene copolymer for uniform hybridization of a piezoelectric film, and (3) increment of the piezoelectric phase via induced crystallization at a low annealing temperature. This dopamine-assisted low-temperature annealing strategy for a hybrid piezoelectric film with a high d33 value (∼31.56 pC/N, 30.56% larger than that of a pure piezoelectric polymer film) required no additional high-voltage polarization treatment and effectively avoided the delamination, distortion, or melt phenomenon between the piezoelectric layer, flexible electrode, and plastic protective layer caused by the high temperature and thermal stress. The obtained FPENGs showed significantly enhanced output performance and mechanical robustness under repeated impact and large amounts of strain conditions. Their specific output voltage and charge density were stably maintained at 7.16 V and 2.40 nC/cm2, which were 30.7 and 50.0% higher than those of FPENGs based on a pure piezoelectric polymer film, respectively. They were further used as biomechanical energy harvesters for generating electricity to charge capacitor energy storage devices for power electronics and self-powered sensors for visual motion-detecting systems, indicating their promising applications in both wearable technology and smart homes.

Improving the piezoelectric properties of CBN‐based ceramic by a Ce ion

AbstractCaBi2Nb2O9 (CBN), one of the bismuth‐layered structural ferroelectrics, with high Curie temperature (TC), has great potential in high‐temperature applications. In this work, high Curie temperature and piezoelectric constant (d33) are realized in modified CaBi2Nb2O9 ceramics with Ce‐substitution. Ce‐substitution changes the crystal structures and domain structures of CBN‐based ceramics, so as to improve the piezoelectric properties. The optimal performances are obtained with a high d33 value (∼18.0 pC/N) and a TC value (∼930°C), together with a low tan δ value (∼0.028 at 500°C). Moreover, the thermal stability is also enhanced, where the d33 value maintains 93.9% of its original value after annealing at 900°C for 2 h. Thus, these findings play a meaningful role in devices manufacturing, where the apply temperature is often more than 500°C.

Effect of Microwave-Assisted Synthesis and Sintering of Lead-Free KNL-NTS Ceramics.

Lead-free piezoelectric powders (K0.44Na0.52Li0.04)(Nb0.82Ta0.10Sb0.04)O3 were obtained by conventional and microwave-assisted reactive heating. Firstly, the synthesis of the material was carried out following the mixed oxide route and employing both traditional methods and microwave technology. Thermogravimetry, X-ray diffraction, field emission scanning electron microscopy and electrical properties analyses were evaluated. X-ray diffraction of the powders calcined by the microwave process shows the formation of perovskite structure with orthorhombic geometry, but it is possible to observe the presence of other phases. The presence of the secondary phases found can have a great influence on the heating rate during the synthesis on which the kinetics of the reaction of formation of the piezoelectric compound depend. The calcined powder was sintered at different temperatures by conventional and non-conventional processes. The microstructure of the ceramics sintered by microwave at 1050 °C for 10 min shows perovskite cubes with regular geometry, of size close to 2–5 µm. However, the observed porosity (~8%), the presence of liquid phase and secondary phases in the microstructure of the microwave sintered materials lead to a decrease of the piezoelectric constant. The highest d33 value of 146 pC/N was obtained for samples obtained by conventional at 1100 °C 2 h compared to samples sintered by microwave at 1050 °C 10 min (~15 pC/N).

Meticulously tailoring phase boundary in KNN‐based ceramics to enhance piezoelectricity and temperature stability

AbstractAlthough KNN‐based ceramics with high electrical properties are obtained through a variety of strategies, the temperature sensitivity is still one of the key technical bottlenecks hindering practical applications. Here, we use a new strategy, meticulously tailoring phase boundary, to refine the ferroelectric boundary of KNN‐based ceramics, leading to high piezoelectricity companied with improving temperature stability. The highest d33 value in this system reaches 501 pC/N with a TC ∼ 240°C, whereas a large strain of ∼0.134% can be kept with 10% lower deterioration until 100°C. The origin of high piezoelectricity is mainly attributed to the well‐preserved multiphase coexistence and the appearance of nanodomains, which greatly facilitate the polarization rotation. Instead of the changed intrinsic thermal insensitivity, the precision phase boundary engineering plays an important role in strengthening the temperature stability of electric‐induced strain. This work provides a simple and effective method to obtain both high electrical properties and excellent thermal stability in KNN‐based ceramics, which is expected to promote the practical applications in the future.

Phase transition and piezoelectric property of (Ag,K)NbO3 ceramics

AgNbO3 is an antiferroelectric (AFE) material with double hysteresis loop. Both the antiferroelectricity and ferroelectricity can be enhanced by doping. Herein, the ferroelectricity of AgNbO3 ceramics was enhanced via K-doping and the phase diagram of the (Ag1-xKx)NbO3 ceramics was upgraded. In details, (Ag1-xKx)NbO3 ceramics are ferrielectric (FIE) M1 phase as x = 5.00–5.50 mol% and ferroelectric (FE) O phase as x = 5.75–6.00 mol% before poling, and FE O phase as x = 5.00–6.00 mol% after poling at room temperature. With increasing temperature, (Ag1-xKx)NbO3 ceramics show the phase evolutions from FIE M1, AFE M2 to paraelectric (PE) T phase at x = 5.00–5.50 mol% and from FE O, FE T to PE T phase at x = 5.75–6.00 mol% before poling, and from FE O, FE T to PE T phase at x = 5.00–6.00 mol% after poling. High d33 values of 180 pC/N and 285 pC/N are obtained at the FE O-FE T and FE T-PE T phase boundaries. This work sheds light on a novel and promising lead-free piezoelectric system.

Structure and electrical properties of Ce-modified Ca1-Ce Bi2Nb1.75(Cu0.25W0.75)0.25O9 high Curie point piezoelectric ceramics

Ca1-xCexBi2Nb1.975(Cu0.25W0.75)0.025O9 (CBNCW-xCe: x = 0.00, 0.02, 0.04, 0.06, and 0.09) lead-free piezoelectric ceramics with improved piezoelectric properties were prepared by the traditional solid-state reaction method. The effects of CeO2 doping on the microstructure and electrical properties were investigated in detail. XRD patterns and Rietveld refinement show that the crystal structures of the samples transform from the orthorhombic phase into the pseudotetragonal phase and that the lattice distortion is weakened. Raman and XPS spectra indicate that Ce ions exist with +3 and + 4 valences in the air sintered ceramics, in which Ce4+ replaces Nb5+, causing the weakened NbO6 octahedral vibration of torsional and tensile and an increase in oxygen vacancies in the doped ceramics. When x = 0.04, it shows excellent comprehensive properties with a high d33 value of 18.1 pC/N, a Tc value of 900 °C, and a ρdc value of 2.8 × 105 Ω cm at 500 °C. Our results suggest that the CBNCW-0.04Ce ceramic is a promising candidate in high-temperature piezoelectric applications.