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AbstractThis paper proposes an efficient technique for the fabrication of macro fiber composite (MFC) and characterizes the properties of MFC under dynamic voltage. First, the fabrication process is described in detail. Then, the effects of peak-to-peak value, frequency and dc bias on the electric-field-induced strain are analyzed. Finally, the mechanical properties are evaluated based on the mixing rules, and the prediction model of electrical parameters is established using the fitting functions. The experimental results show that the proposed fabrication technique effectively suppresses the generation of defects and the electric field variation has significant effects on the actuating properties. [ABSTRACT FROM AUTHOR]

CaBi 2 Nb 2 O 9 (CBN) is a bismuth layered ferroelectric material with extremely high Curie temperature and low dielectric loss, which has great application potential in ultra-high temperature field. However, because of its low piezoelectric coefficient, its practical application still faces great challenges. This study successfully prepared Ca 1-x Ce x Bi 2 Nb 1.98 (W 2/3 Mn 1/3) 0.02 O 9 (x = 0–0.05) two-layer ferroelectric ceramics using direct-reaction sintering method. A pseudo tetragonal structure was successfully constructed near x = 0.02 using the substitution method of Ce4+ at site A, and W6+ and Mn4+ at site B, which altered the crystal structure of CBN based ceramics. The properties of CBN-based piezoelectric ceramics have been significantly improved by this modification. It has a higher piezoelectric constant (d 33 = 20.6 pC/N) and Curie temperature (T c = 950 °C), while having a lower dielectric loss (tan δ = 0.031 at 500 °C). In addition, CaBi 2 Nb 2 O 9 based piezoelectric ceramics also show excellent thermal stability. After annealing at 900 °C for 2 h, the d 33 value remained high at 19.2 pC/N, retaining about 93.2% of its original value. Therefore, these findings indicate that Ca 1-x Ce x Bi 2 Nb 1.98 (W 2/3 Mn 1/3) 0.02 O 9 is a high-temperature piezoelectric material with great potential. [ABSTRACT FROM AUTHOR]

Although BiFeO 3 –BaTiO 3 -based lead-free ceramics have attracted much attention in recent years as a high temperature piezoelectrics, their d 33 value is still difficult to exceed 200 pC/N through conventional methods. In this work, a novel (0.7-x)BiFeO 3 -0.3BaTiO 3 -xLa(Mg 2/3 Nb 1/3)O 3 (x = 0–0.005) ternary system was reported to own excellent room-temperature piezoelectric constant (d 33) ∼216 pC/N and high Curie temperature (480 °C) at x = 0.003 simultaneously. It reveals that the compositions undergo an obvious phase transition from ferroelectric (FE) rhombohedral (R) phase to relaxor pseudo-cubic (PC) phase via an R–PC morphotropic phase boundary (MPB). More importantly, piezoelectric nonlinear Rayleigh analysis and S-E/P-E curves suggest that the significantly enhanced domain dynamics due to the coexistence of macrodomain and nanodomain can be observed in the x = 0.003 sample. The synergy of these two effects induce the improved d 33 value observed in the x = 0.003 sample. In addition, the compositions exhibit the inhibition of defect dipoles and the improvement of the high temperature resistivity, leading to the excellent thermal stability with sensitivity coefficients ƞ less than ± 5% in the annealing temperature range of 25–400 °C. The present work provides a guideline for the subsequent design of high-temperature lead-free ceramics. [ABSTRACT FROM AUTHOR]

Electrical poling is a very important process for ferroelectrics before exploiting their piezoelectric properties. However, difficulties are encountered in poling ferroelectrics with a high coercive electric field. Here, we report a method to pole ferroelectric ceramics by firstly applying uniaxial stress (US) parallel to the direct current poling electric field (DC), then applying the DC after the US unloading, and lastly applying biaxial transverse compressive stresses (BTCS) with the DC hold. Both of the calculation and experiment results demonstrate that the proposed method allows a significant decrease in the electric field necessary for poling. The obtained d 33 of the specimens poled by the proposed method at electric field of 1.25 E c is close to the same material poled at high temperature. The proposed method is thought to be possible to offer solution to ferroelectrics that are hard to be poled, e.g., high-temperature ferroelectric ceramics. [ABSTRACT FROM AUTHOR]

A notoriously unresolved conflict that the substantial increment of depolarization temperature T d was generally accompanied by the sharply deterioration of piezoelectric constant d 33 in Bi 0.5 Na 0.5 TiO 3 -based (BNT-based) piezoceramics severely limit their practical applications. Herein, a new strategy by Ba2+ gradient diffusion layer in 0.94Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 (BNT-6BT) ceramic via interface-diffused sintering to suppress the ferroelectric-relaxor phase transition is presented to manipulate the incompatibility of T d and d 33. By this strategy, the compositionally graded diffusion in the BNT-6BT ceramic can offer both the properties simultaneously with the T d deferring from 109 °C to 170 °C and maintaining the initial d 33 (145pC/N). Furthermore, by integrating the interface-diffused sintering and quenching process, the T F-R is significantly deferring from 115 °C to 214 °C while the d 33 * is retaining the initial value (d 33 *=S max /E max =258 pm/V). Diffusion phase transition caused by Ba2+ concentration gradient promotes the greatly increased tetragonal phase ratio and the development of built-in field thereby leading to well-balanced performance between T d and d 33 in BNT-6BT ceramic. Our work opens a new avenue for developing the high-performance lead-free BNT-based piezoceramics. [ABSTRACT FROM AUTHOR]

High Curie-temperature layer-structured calcium bismuth niobate (CaBi 2 Nb 2 O 9) piezoelectric ceramics are promising for important application in high-temperature vibration sensors. However, such application is currently limited due to not only poor high-temperature piezoelectric constant (d 33), which is attributable to spontaneous polarization along a - b plane and high coercive fields, but also inferior high-temperature electrical resistivity, which results from volatilization of Bi 2 O 3 during the sintering process that increases defect concentration of oxygen vacancies. Herein, we report a Na+, Bi3+ and La3+ ternary-doping-strategy to obtain Ca 0.8 (Na 0.5 La 0.3 Bi 0.2) 0.2 Bi 2 Nb 2 O 9 ceramics, which exhibited higher piezoelectric constant and larger electrical resistivity as accompanied by a better thermal stability at high-temperatures. The piezoelectric constant was enhanced from 8.8 pC/N in pristine CaBi 2 Nb 2 O 9 to 13.4 pC/N in Ca 0.8 (Na 0.5 La 0.3 Bi 0.2) 0.2 Bi 2 Nb 2 O 9 ceramics, which is ascribed to the presence of pseudo-tetragonal structural distortion after La3+ doping. In addition, the electrical resistivity at 600 °C was increased by more than one-order of magnitude from 3.7 × 104 Ω cm in pristine CaBi 2 Nb 2 O 9 to 1.4 × 106 Ω cm in Ca 0.8 (Na 0.5 La 0.3 Bi 0.2) 0.2 Bi 2 Nb 2 O 9 ceramics. Such significant improvement in electrical resistivity results from the reduction in oxygen vacancies due to ternary doping of Na+, Bi3+ and La3+ and stronger binding interaction between La3+ dopants and O2− in (Bi 2 O 2)2+ layers in Ca 0.8 (Na 0.5 La 0.3 Bi 0.2) 0.2 Bi 2 Nb 2 O 9 ceramics. This work demonstrates an important way of employing chemical doping to improve piezoelectric constant and electrical resistivity simultaneously at high-temperatures to tune structural distortion in bismuth-layered structural CaBi 2 Nb 2 O 9 ceramics. [ABSTRACT FROM AUTHOR]

The application of piezoelectric ceramics at high temperature is limited because they can't have both high piezoelectric coefficient and high Curie temperature. While, BiScO3–PbTiO3-based piezoelectric ceramics possessing high Curie temperature and piezoelectric properties simultaneously have drawn increasing attention due to their potential applications at high temperature. Here, we reported a novel compositional design of (1-x)[0.36BiScO3-0.64PbTiO3]-xBi(Sn1/3Nb2/3)O3 (abbreviated as BS-PT-xBSN). BS-PT-xBSN ceramic samples were synthesized by conventional solid state reaction method. According to the ternary phase diagram of BS-PT-xBSN ceramics brought up in this work, the morphotropic phase boundaries (MPB) were confirmed, which is located in the vicinity of x = 0.02. It canbe identified that the x = 0.02 sample near MPB has the optimal electric performance which are giant piezoelectric coefficient (d33 ∼ 450 pC/N, higher 18 % than undoped samples) and high Curie temperature (Tc ∼ 368 °C) as well as large remant polarization (Pr ∼ 46.6 μC/cm2). In addition, the variation of Pr is 3 % in the temperature range of 30–180 °C and the depolarization temperature of x = 0.02 ceramics is about 280 °C. Structural analysis such as in-situ PFM and TEM confirms that giant piezoelectricity and depolarization temperature are attributed to the appearance of nano-domain and complexity of domains as well as the stable domain configuration. This work not only reveal the high potential of BS-PT-xBSN for high-temperature piezoelectric applications but also open up a feasible approach to design new high-temperature piezoelectric ceramics.

In this work, pellet samples of barium calcium zirconate titanate (Ba1-xCaxZr0.1Ti0.9O3, x=0.065) were prepared using solid state reaction route with double sintering. The structural and piezoelectric properties were measured. Further, SEM and EDAX analysis were observed. With different sintering temperature, the density and grain size of the prepared pellet samples were changed and further, their effect in piezoelectric properties has been observed. For the prepared samples, the converse piezoelectric constant (d33*) has been decreased with the increase in sintering temperature. The piezoelectric constant (d33*) was measured highest (153 pm/V) at 1300°C.

CaBi2Nb2O9 (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. [ABSTRACT FROM AUTHOR]

Investigating piezoelectricity of nano/microwire is important for their applications in nanogenerator, actuator, sensor and many more. Up to now, accurately probing the piezoelectric constant of nano/microwire along its axial direction has remained a challenge. Here, we propose a strategy that can high-precisely characterize the piezoelectric constant of nano/microwire along its axial direction through constructing a lateral structure with short connection of two ends of nano/microwire as one electrode and probe tip as another electrode, making the nano/microwire not buckle and its length unchanged during measurements. Theoretical analysis and simulations show that this strategy has ultra-high precision, in which the error can be as low as 2% (aspect ratio ∼100), 0.3% (∼500) and less than 0.2% (∼1000). Using this strategy, the measured piezoelectric constant d 33 of ZnO microwires is 12.31 ± 0.57 pm/V, highly consistent with widely accepted values in ZnO bulks and films, further verifying the correctness and accuracy of this strategy. This simple, universal and high-precision strategy contributes to the piezoelectric characterization of nano/microwires and their applications in energy harvesting, human-machine interfacing, active electronics/optoelectronics and many more. [Display omitted] • A strategy is developed for high-precisely measuring piezoelectric constants of nano/microwires along its axial direction. • The design deforms the nano/microwire with its whole length unchanged to piezoresponse to achieve high-precise measurement. • Ultra-low error less than 0.2% is realized here, which is one order smaller than the error caused by conventional methods. [ABSTRACT FROM AUTHOR]

Copyright of Science of Sintering is the property of National Library of Serbia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BiFeO 3 –BaTiO 3 –based solid solutions are promising candidates for high–temperature piezoelectric devices because of their high Curie temperature (T C) and considerable electrical properties. Here, we reported an optimum composition of 0.7Bi(Fe 0.999 Mn 0.001)O 3 –0.3BaTiO 3 ceramic with a large piezoelectric constant (d 33) of 230 pC/N and a high T C of 505 °C, which was attributed to the intentional introducing of the ceramic with MnO and MnO 2 mixture. Furthermore, an in situ d 33 measurement was carried out, demonstrating excellent thermal stability for the 0.7Bi(Fe 0.999 Mn 0.001)O 3 –0.3BaTiO 3 specimen. The d 33 remained above 200 pC/N in the temperature range of 25 °C–400 °C and its fluctuation was less than ± 15 %. It was determined that the high d 33 in the 0.7BiFe 0.999 Mn 0.001)O 3 –0.3BaTiO 3 ceramic originated from a synergistic effect of rhombohedral distortion, intrinsic response, and ferroelectric order. The findings establish a solid correlation between electrical properties and phase/domain structure, and provide a novel approach to improve the piezoelectric properties for BiFeO 3 –BaTiO 3 –based ceramics. [ABSTRACT FROM AUTHOR]

Ceramic pellet samples of (Ba1-xCaxZr1-yTiy)O3 (x = 0.140-0.160, y = 0.9), were prepared using the conventional solidstate reaction method followed by double sintering. Structural and piezoelectric measurements of the prepared compositions were carried out at room temperature. For the compositions with x ≤ 0.150, the converse piezoelectric constant (d33*), strain (%), coercive field (Ec) and remnant polarization (Pr), were found increasing with x, which were found anomalously to decrease with further increase in x above 0.150. Among the prepared compositions, maximum value of d33* was found 342 pm/V, for the samples with x = 0.150. The measured maximum values of strain (%), piezoelectric constant (d33*) and break in XRD peak shifting patterns of the prepared samples indicate composition dependent piezoelectric properties, showing morphotropic-like phase boundary (MPB), near x = 0.150 composition. The prepared compositions of lead-free BCZT ceramics will extend the possibilities to use this compound in the field of piezoelectric sensors. [ABSTRACT FROM AUTHOR]

The goal of the current report was to find the optimal poling conditions: poling field, poling time and poling temperature for lead-free (Ba0.85Ca0.15Zr0.1T0.9)O3 ceramic. It has been noticed that the low poling field (< 2 kV/mm) was insufficient for obtaining ideal poling state (θ = 90°) due to the incomplete switching of domains and thus low piezoelectric properties (d33 ≤ 438 pC/N and kp ≤ 49%). However, relevance of higher poling voltage (> 2 kV/mm) may induce electric breakdown and physical defects such as cracks in the sample, which also leads degradation of piezoelectric properties. The optimal poling field, poling time and poling temperature was found to be 2 kV/mm, 10 min and 24°C, i.e., near room temperature, respectively to achieve nearly ideal poling state (θ = 86°) obtained by impedance spectra, and thus enhanced piezoelectric constant d33 = 505 pC/N and kp = 56% at room temperature. The O-T phase transition point was identified at 32.6°C, for which a peak value of d33(E=0V) = 622 pm/V was realized.

Recent studies have reported that lead-halide perovskites are the most efficient energy-harvesting materials. Regardless of their high-output energy and structural stability, lead-based products have risk factors due to their toxicity. Therefore, lead-free perovskites that offer green energy are the expected alternatives. We have taken CsGeX 3 (X = Cl, Br, and I) as lead-free halide perovskites despite knowing the low power conversion rate. Herein, we have tried to study the mechanisms of enhancement of energy-harvesting capabilities involving an interplay between structure and electronic properties. A density functional theory simulation of these materials shows a decrease in the band gaps, lattice parameters, and volumes with increasing applied pressure. We report the high piezoelectric responses and high electro-mechanical conversion rates, which are intriguing for generating electricity through mechanical stress., (© 2024 IOP Publishing Ltd.)

PbNb 2 O 6 (PN)-based piezoceramics are considered important materials used in high temperatures. Whereas, the main problem of PN-based ceramic is its low electrical performance such as piezoelectric constant (d 33), severely restricting its practical applications. Here, based on the principle of regulating structure and performance via defect engineering, a new way of artificially tailoring point defects by A-site nonstoichiometry is implemented in this study. The results show that the PN-based ceramics with A-site deficiency exhibit significantly enhanced dielectric and piezoelectric properties. Particularly, the relative dielectric permittivity (ε r) increased by 165% (from 197 to 523) and the d 33 increased by 177% (from 30 to 83 pC/N) while maintaining a high Curie temperature (T C ~ 543 °C), and the resultant superior comprehensive performance is nearly highest in PN-based ceramic system. The X-ray photoelectron spectrometer and Raman spectra reveal that A-site deficiency leads to a decreased level of oxygen vacancies and NbO 6 octahedral distortion as well as disorderly motions of A-site cations, which further causes the markedly decreased domain size exhibited in piezoresponse force microscopy (PFM) images. Consequently, the improved domain structure gives rise to improved dielectric and piezoelectric properties. The results of this work provide a simple and effective strategy to improve the dielectric and piezoelectric properties while keeping a high T C in the PN-based ceramics system, meeting the urgent demands of high-temperature applications. [ABSTRACT FROM AUTHOR]

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] Lead-free piezoceramics based on the (Ba, Ca)(Zr, Ti)O 3 (BCZT) system provide outstanding electromechanical characteristics for low-temperature actuation applications, however manufacturing temperatures are a little high. Here, we demonstrate how calcium doping can simultaneously enhance Ba(Zr, Ti, Sn)O 3 piezoceramics' electromechanical strain response for the MPB composition(s) with formula (Ba 1-x Ca x)(Ti 0.85+x Zr 0.02 Sn 0.13-x)O 3. The electromechanical, dielectric, and ferroelectric properties of the samples, which were created utilizing solid state synthesis techniques, were all investigated. The sample with the highest d* 33 value, 748 pm/V for 0.26 kV/mm and 645 pm/V for 0.62 kV/mm, had 0.070 mol% Ca substituted on the perovskite lattice's A-site, which also demonstrated the best dielectric and piezoelectric performance in the composition range for 0.070 ≤ x ≤ 0.090. The ceramic with electromechanical coefficient (kp) = 44.6 % also displays the greatest values of large electrostrictive coefficients (Q 33 ≈ 0.10 m4/C2) that also observed in these Ca, Zr and Sn doped Ba(Zr,Ti, Sn)O 3 ceramics. [ABSTRACT FROM AUTHOR]

This work shows for the first time the possibility to sinter BCZT powder compacts by rapid heating rates within one hour of sintering, while achieving good piezoelectric properties. The sintering was performed by rapid (heating rates 100 and 200 °C/min) pressure-less sintering (PLS) at 1550 °C/5-60 min and by SPS sintering (100 °C/min, 1450 °C/5−60 min and 1500 °C/15−45 min). The rapid PLS samples reached a relative density up to 94 % and grain sizes of 17–36 μm acquiring d 33 up to 414 pC/N. Although the SPS samples reached full density at 1450 °C, their piezoelectric properties worsened due to smaller grains (10−15 μm) as well as formation of cracks at dwell times > 30 min. At elevated SPS temperature of 1500 °C/30 min, the d 33 increased to 360 pC/N sustaining full density. Even higher increase in d 33 (424 pC/N) of SPS samples was achieved by post-rapid PLS at 1550 °C/60 min resulting from further expansion in grain size. [ABSTRACT FROM AUTHOR]

The goal of the current report was to find the optimal poling conditions: poling field, poling time and poling temperature for lead-free (Ba0.85Ca0.15Zr0.1T0.9)O3 ceramic. It has been noticed that the low poling field (< 2 kV/mm) was insufficient for obtaining ideal poling state (θ = 90°) due to the incomplete switching of domains and thus low piezoelectric properties (d33 ≤ 438 pC/N and kp ≤ 49%). However, relevance of higher poling voltage (> 2 kV/mm) may induce electric breakdown and physical defects such as cracks in the sample, which also leads degradation of piezoelectric properties. The optimal poling field, poling time and poling temperature was found to be 2 kV/mm, 10 min and 24°C, i.e., near room temperature, respectively to achieve nearly ideal poling state (θ = 86°) obtained by impedance spectra, and thus enhanced piezoelectric constant d33 = 505 pC/N and kp = 56% at room temperature. The O-T phase transition point was identified at 32.6°C, for which a peak value of d33(E=0V) = 622 pm/V was realized. [ABSTRACT FROM AUTHOR]

The work discussed is developing a self-sustainable low-power remote multi-sensing and data logging system for traffic sensing. The system is powered by the energy harvested using a stacked PZT (Lead zirconate titanate) transducer from the mechanical vibration from the vehicles passing over roads. The system is capable of multi-sensing functionality, logging the sensor data, and wirelessly transferring sensory data to an end-user device. Various power management techniques and engineering applications were made to achieve low power operation of the system while maintaining the full functionality and the accuracy of the sensor data. The energy harvester used is a custom-designed and fabricated stacked piezoelectric transducer optimized for maximum energy harvesting from the mechanical vibration from roadway traffic. A custom-built AC to DC converter is used to convert the harvested energy into useable electrical power. The system was tested under various experimental setups yielding satisfactory data accuracy while operating at low power. The system also successfully transferred sensor data remotely. All these features make the system self-sustainable and suitable for remote sensing applications without a conventional power source.

(Bi 1/2 Na 1/2)TiO 3 -based materials have received much attention due to large electro-strain and high piezoelectric constant (d 33), but the tough issue is that the existence of inherent depolarization temperature (T d) limits the temperature stability and application temperature range. Previously, reports about the formation of BNT/oxide (i.e., ZnO, Al 2 O 3) composites thought that T d can be deferred to a higher temperature and then thermal depolarization improves. However, the deferred T d of BNT/oxide composites is limited, accompanied by a low d 33. Here, we design the {[Bi 0.5 (Na 0.8 K 0.2) 0.5 ] 1- x Pb x }TiO 3 ceramics, leading to a big shift of T d from 77 ℃ to 390 ℃. Large d 33 (140 pC/N) and high T d (∼263 ℃) can be simultaneously achieved for the sample with Pb=0.05, and T d could be further deferred higher (390 ℃) for Pb=0.20. The off-centre displacement of Pb induced by Pb-O hybridization in the PbO 12 polyhedron and ferroelectric order stabilized by the addition of Pb can provide the driving force to strengthen the ferroelectric order, and then promote the thermal stability. [ABSTRACT FROM AUTHOR]

The influence of double sintering temperature on the phase structure, micro-structure and piezoelectric properties of Ba1-xCaxZr0.1Ti0.9O3 (x = 0.055) double sintered ceramics has been systematically studied. The pellet sample preparation and characterization have been reported in this paper. The converse piezoelectric properties of the Ba1-xCaxZr0.1Ti0.9O3 (x = 0.055) were observed. Depending upon the sintering temperature, the grain size and density of BCZT ceramics have been changed. The P-E loops, strain%, and the polarization current were measured. The value of d33 was decreasing with the application of an electric field in case of double sintered pellets. For sample x = 0.055, the value of d33* at 1300, 1400 and 1450 °C temperature, was 173 (pm/V), 130 (pm/V), and 75 (pm/V), respectively, at applied field 29.33 kV/cm. [ABSTRACT FROM AUTHOR]

As one of the most promising candidates of high‐temperature piezoelectric sensors, BiScO3‐PbTiO3 (BS‐PT)‐based ceramics are commonly modified by end‐member substitution to modify the phase structures and electrical properties. In this work, BS‐PT‐based piezoelectric ceramics with various grain sizes (1.4‐3.7 μm) of the composition 0.98(0.36BiScO3‐0.64PbTiO3)‐0.02Bi(Sn1/3Nb2/3)O3 were prepared by conventional solid‐state reaction method at different sintering temperatures from 1100℃ to 1180℃. X‐Ray diffraction results show that the tetragonal phase content increases from 68.9% to 85.7% with the increasing sintering temperature. Transmission electron microscope characterizations reveal that micromorphology and domain morphology are sensitive to grain size. In addition, the dielectric and ferroelectric properties are almost independent on the sintering temperature, whereas an optimal piezoelectric constant d33 of 450 pC/N is achieved when the sintering temperature is 1120℃, which can be due to the suitable coexistence of the rhombohedral and tetrahedral phase, as well as the coexistence of nanodomains and subsize strip‐like domain. All of the results not only open a new window to improve d33 of piezoelectric ceramics but also help to further understand microstructure‐property relationships in piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Deriving from strong temperature dependence of polymorphic phase boundaries, piezoelectric constant of potassium sodium niobate (K0.5N0.5NbO3)‐based ceramics is sensitive to the poling temperature. Here, an effective strategy of doping rare earth (RE) elements is proposed to solve this issue. Piezoelectric constant (d33 ~ 440 pC/N) can be well kept in 0.965K0.45Na0.55Nb0.96Sb0.04O3‐0.035(Bi0.75Dy0.25)0.5Na0.5HfO3 ceramics at a wide poling temperature range (35‐120°C) by the method of replacing Bi3+ with rare earth dysprosium, and importantly, this method can be effectively expanded to other RE elements. The high piezoelectricity roots in the multiphase coexistence with the addition of RE elements. The dull sensitivity of poling temperature is analyzed by microstructure information, that is, ferroelectric domains can be well rotated under a wide temperature range by introducing RE, which is responsible for the stabilized piezo‐response against the poling temperature. Moreover, comparing with Bi3+, a lower electronegativity of RE3+ may effectively reduce the micro‐stress produced by lattice distortion, also yielding to the lattice softening and the easier domain rotation. [ABSTRACT FROM AUTHOR]

BACKGROUND: Our previous study confirmed that BTO/P(VDF-TrFE) piezoelectric nanocomposita membrane containing 5%BTO (BaTO3, BTO) nanoparticles could significantly promote bone marrow mesenchymal stem cells (BMSCs) adhesion, growth, osteogenic differentiation and repair of bone defects due to its bionic potential. However, for clinical applications, it is not clear whether there is any difference between the bone repair effect of this material as a guide for tissue regeneration and that of the existing clinically non-degradable membrane products. OBJECTIVE: To compare the effects of BTO/P(VDF-TrFE) piezoelectric nano-composne membrane materials with commercial PTFE membrane in repairing critical-sized defects of SD rat skull. METHODS: BTO/P(VDF-TrFE) piezoelectric nanocomposne membrane containing 5% BTO nanoparticles was prepared by solution casting method. Scanning electron microscope, atomic force microscope and water contact angle measuring instrument were used to observe the surface morphology, measure the surface roughness and surface hydrophilicity and hydrophobicity of the material. In SD rats (purchased from the Laboratory Animal Center, Beijing University Hospital of Stomatology, China), a 5-mm sized full-thick bone defect was made on both sides of the sagittal suture of the skull. The left bone defect was covered with PTFE membrane (control group). The right bone defect was covered with BTO/P(VDF-TrFE) piezoelectric nano-composita membrane (experimental group). At postoperative 4 and 12 weeks, micro-CT and histological methods were used to evaluate the repair of the skull defect in rats. This study was approved by Animal Ethics Committee, Beijing University Hospital of Stomatology. RESULTS AND CONCLUSION: The piezoelectric nanocomposite membrane had smooth and dense surface and BTO nanoparticles were evenly distributed. PTFE membrane was composed of loose coarse fibers. The piezoelectric nanocomposite membrane had lower surface roughness (P< 0.001) and higher hydrophilicity (P< 0.001) than PTFE membrane. Micro-CT and histological results showed that at 4 weeks after surgery, new bone formation was found in both groups, but new bone formation was more obvious in the center of the defect in the experimental group than in the control group. At 12 weeks after surgery, bone defects healed in both groups, but the maturity of newly formed bone in the experimental group was greater than that in the control group. These results suggest that BTO/P(VDF-TrFE) piezoelectric nanocomposite membrane containing 5%BTO (BaTO3, BTO) nanoparticles can be used as a membrane guiding tissue regeneration. [ABSTRACT FROM AUTHOR]

In order to obtain excellent electrical properties and its temperature stability of KNN‐based ceramics to meet the practical applications, a new lead‐free material system of (1−x)K0.5Na0.5Nb0.96Sb0.04O3‐xBi0.5Na0.5Zr0.8Sn0.2O3 (KNNS‐xBNZS, 0 ≤ x ≤ 0.060) was designed, and the enhanced electrical properties (eg, d33 ~ 465 pC/N, εr ~ 3318, Suni ~ 0.133%) is obtained in the ceramics with x = 0.04. The physical origin of enhanced electric properties should be ascribed to the phase instability of R‐T, resulting in a low‐energy barrier, which can greatly facilitate the polarization switching. Moreover, the temperature stable of piezoelectric constant (d33 or d33*) is measured by three distinctive methods in different phase boundaries (O, O‐T, R‐T) at the temperature range 20°C‐180°C, revealing that the O‐T phase boundary has a relatively good temperature stability. A mode is used to show how to effectively modified the piezoelectric constant (d33 or d33*) and its temperature stability, we believe that such a strategy may further improve the temperature stability of d33 or d33* value in KNN‐based ceramics. [ABSTRACT FROM AUTHOR]

The sol--gel technique is a major deposition method of lead zirconate titanate (PZT), because of its good uniformity and simplicity. At present, different PZT sols are commercially available, and users are interested in which sol best fits their application and deposition tool. In this study, PZT thin films were deposited using different commercial sols, and their characteristics were evaluated and compared in terms of film thickness, crystal orientation, and ferroelectric property. We found that a rapid thermal annealing (RTA) temperature of 650 °C and a drying temperature of 180 °C were suitable as starting conditions regardless of the PZT sol. Under these conditions, the piezoelectric constant d31 is more than 75 pm/V. Optimization can be carried out efficiently by each user under these conditions. [ABSTRACT FROM AUTHOR]

It is difficult to realize the balanced development of piezoelectric response {piezoelectric constant (d 33) and strain} and temperature stability of potassium-sodium niobate ceramics. Here, we constructed one kind of lead-free piezoceramic system of 0.965K 0.45 Na 0.55 Nb 0.96 Sb 0.04 O 3 -0.035(Bi 1- x Ho x) 0.5 Na 0.5 HfO 3 , and rhombohedral & tetragonal (R-T) multiphase coexistence maintains in a wide compositional range of x = 0.05–0.55. Greatly improved temperature stability of piezoelectric response is realized by doping rare earth Ho. Excellent temperature stability of both strain and d 33 mainly originates from the weak temperature dependence of domain structure as well as the increased R-T phase transition temperature. As a result, the addition of rare earth Ho can boost temperature stability of potassium-sodium niobate-based ceramics. Image 1 • Superior temperature stability of piezoresponse is achieved in KNN ceramics. • Weak temperature dependence of domain structure matches the stable piezoresponse. • Increased phase transition temperature contributes the good temperature stability. [ABSTRACT FROM AUTHOR]

Fine powders synthesized via sol‐gel route were employed to fabricate Sr(2−x)(Na0.5Bi0.5)xBi4Ti5O18 (SNBT, where x = 0, 0.1, 0.25, 0.3, 0.4, and 0.5) ceramics. The composition (x)‐dependent structural changes associated with SNBT ceramics were analyzed using X‐ray powder diffraction, transmission electron microscopy, and Raman spectroscopic techniques. Average grain size analyses carried out on the SNBT ceramics by scanning electron microscopy revealed an important role played by the dopants in inhibiting the grain growth. Dielectric constants and the Curie temperature of the ceramics were found to decrease and increase, respectively, with increase in x. The increase in Curie temperature with increase in x was attributed to the decrease in the tolerance factor. The specific composition (x = 0.3) of the SNBT ceramics exhibited improved piezo‐ and ferroelectric properties associated with a higher Curie temperature (569 K). The piezoelectric coefficient (d33) and the planar electromechanical coupling coefficient (kp) of SNBT(x = 0.3) were enhanced by 25% and 42%, respectively, as compared to the undoped ceramics. [ABSTRACT FROM AUTHOR]

Piezotronic and piezophototronic devices have attracted increasing interests in self-powered sensor, piezotronic logic units and flexible energy-harvesting devices. The carrier transport characteristics can be effectively tuned by the piezoelectric charges induced by an externally applied strain, which has been extensively investigated for a uniform strain case. However, a non-uniform strain can induce a giant piezoelectric field at the interface to significantly enhance the piezotronic effect. In this paper, we propose a model that a mechanical stress is gradient distributed along a piezoelectric-semiconductor material. The electric properties of piezotronic p-n junction with non-uniform strain has been simulated by using the finite element method, including the current-voltage characteristics and carrier concentration. The piezotronic p-n junction involving strain gradient possesses ultrahigh sensitivity (the gauge factor over 2500) due to the enhancement of piezoelectric constant. This investigation further broadens the fundamental theory of piezotronics and offers guidance for designing ultrahigh performance piezotronic devices. The piezotronic devices based on non-uniform strain can have ultrahigh performance. The gauge factor of the novel piezotronic p-n junction based on a non-uniform strain can reach over 2.5 × 103. The effective piezoelectric constant of the piezotronic devices with non-uniform strain can be enhanced, and the investigation offers a guidance to design high performance piezotronic device. Image 1 • The piezoelectric constant of the piezotronic device can effectively be enhanced by non-uniform strain. • The gauge factor of the non-uniform strained piezotronic p-n junction can reach up to 2500. • This study extends the theory of piezotronics and piezophototronics. [ABSTRACT FROM AUTHOR]

MnO 2 -doped 0.99(0.36BiScO 3 -0.64PbTi 1- x Ce x O 3 )-0.01Bi(Zn 0.5 Ti 0.5 )O 3 (BS-PTC-BZT-MnO 2 ) ceramics are fabricated by the solid-state method. Here, it's firstly reported that Ce element can reduce dielectric loss (tan δ ) and suppress the decrease of piezoelectric constant ( d 33 ) simultaneously. Effects of Ce contents on the structure and electrical properties of BS-PTC-BZT-MnO 2 ceramics are studied. The ceramics ( x  = 0.02) with MPB (rhombohedral-tetragonal) possess low dielectric loss (tan δ  = 1.36%, 1 kHz) and high piezoelectric constant ( d 33 = 360 pC/N) simultaneously, which is superior to most reported BS-PT. Besides, excellent comprehensive properties including high Curie temperature ( T C = 422 °C), large dielectric constant ( ɛ r = 1324), and high remnant polarization ( P r = 35.1 µC/cm 2 ) are obtained. Asymmetric S-E and P-E hysteresis loops indicate that defects and oxygen vacancies are induced by multi-valence elements (Ce and Mn), which is the origin for reducing tan δ . In addition, good thermal stability of piezoelectric and dielectric properties is observed. These results indicate that Ce and Mn co-doped BS-PTC-BZT-MnO 2 ceramics can be well applied as power electronic devices under high temperature. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN) is an important piezoelectric material for a wide range of applications, but its low piezoelectric coefficient is the main problem it faces. Many efforts are devoted to improving its piezoelectric response by alloying transition metals (TMs). On the basis of the density functional theory, the influence of the type and distribution of TM on the piezoelectric response is discussed in this paper. TM 0.0625 Al 0.9375 N with twenty-eight different TMs are investigated, and most show higher values of piezoelectric strain modulus d 33 than that of AlN. This is because the TM introduces weaker TM-N bonds and locates closer to the centre of three neighbouring N atoms. The location of TM is determined to be significantly correlated with its group number. Alloys of TM x Al 1−x N (TM=Sc, Cr, Sr, Mo, Ru and Rh) with varying x are further studied. On the basis of the cost of the TMs and piezoelectric performances, the alloy with Mo is more effective in enhancing d 33. A high d 33 of 12.3 times that of pure AlN is realized in a metastable configuration of Mo 0.167 Al 0.833 N. The distribution of Mo plays a key role in the piezoelectric performance. A higher d 33 is more likely to appear in Mo x Al 1−x N with more Al sublayers containing Mo atoms and with fewer dimers of Mo atoms along the z -axis. [Display omitted] • Piezoelectric response of AlN is enhanced via alloying of transitional metals (TMs). • Influence of type and distribution of TMs on d 33 is discussed for the first time. • A high d 33 of 12.3 times that of pure AlN is realized in a metastable Mo-alloy AlN. [ABSTRACT FROM AUTHOR]