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X-ray diffraction and dielectric studies were performed on synthesized ceramic samples of the section (1–x) (0.8PbMg 1 ∕ 3 Nb 2 ∕ 3 O 3 ⋅ 0. 2 BiScO3)⋅ x(0.8PbTiO 3 ⋅ 0. 2 BiScO3) with x = 0 –1 of the ternary BiScO3–PbTiO3–PbMg 1 ∕ 3 Nb 2 ∕ 3 O3 (BS–PT–PMN) system, including the temperature dependence of thermally stimulated depolarization currents (TSDC). It was found that the samples are solid solutions with a perovskite structure, which have cubic symmetry in the range of x = 0–0.587 and tetragonal symmetry in the range of x = 0.680–1. In the intermediate composition range of x = 0.587–0.680 (morphotropic region — MR), the samples consist of a mixture of solid solutions of different symmetries. Data on the change in dielectric properties and TSDC(T) dependencies of solid solutions with a change in their composition were obtained. It was found that samples of compositions x =0–0.625 and 0.6875–1 exhibit relaxor-ferroelectric and conventional ferroelectric properties, respectively, while samples of compositions x = 0.625–0.6875 combine ferroelectric and relaxor-ferroelectric properties. [ABSTRACT FROM AUTHOR]

0.39Bi(Ni0.5Ti0.5)O3–0.20PbZrO3–0.41PbTiO3:x(Bi2O3 + PbO) (BNPZT:xBiPb, x = 0, 1, and 2) piezoceramics were prepared via conventional solid-state route. The impact of excess Bi2O3 and PbO on the structural, dielectric, ferroelectric, bipolar strain, and piezoelectric properties of BNPZT ceramics was investigated. The Rietveld refinement results indicated that all sintered ceramics were well crystallized into a pure perovskite structure with major rhombohedral and minor tetragonal phases. The temperature and frequency dependence of dielectric measurements revealed relaxor behavior and a high Curie temperature (Tc ~ 290 °C) for BNPZT:1BiPb ceramics. High remnant polarization (Pr ~ 25.43 μC/cm2), low coercive field (Ec ~ 16.73 kV/cm), and bipolar strain (0.12%) were achieved in BNPZT:1BiPb ceramics. This study outlines a route for exploring new piezoelectric materials with enhanced electrical properties. [ABSTRACT FROM AUTHOR]

This paper studies the structural parameters and electrophysical properties (dielectric and piezo electric, as well as currents of thermostimulated depolarization) of samples of composition 0.20BiScO3·0.45PbTiO3·0.35PbMg1/3Nb2/3O3 (or in short 0.20BS·0.45PT·0.35PMN) obtained by ceramic and melt-hardening methods of synthesis. In the ceramic method, the samples were obtained from the starting oxides by two-stage firing. In the melt method, amorphous precursors were first obtained from heat-treated and non-heat-treated starting oxide mixtures by melting and subsequent quenching under sharply gradient temperature conditions. Samples were obtained after grinding, pressing, and thermal annealing of the synthesized precursors, and four types of samples differing in size and shape of the intermediate precursor particles (crystallites) were obtained. The X-ray phase analysis showed that the predominant phase in the studied samples is the perovskite phase; in both types of samples, up to 5 wt.% of impurity phase with pyrochlore structure was also present. The samples of 0.20BS·0.45PT·0.35PMN exhibit dielectric properties characteristic of relaxor ferroelectrics, and the polarized samples exhibit a pronounced piezo effect with a piezo modulus value of d33~200 pC/N. A comparative analysis of the properties of the samples obtained by different methods has been carried out. The essential advantage of the melt method is that its use allows obtaining varieties of four kinds of ferroelectric relaxors and reduces the time of synthesis of samples by 2–3 times. [ABSTRACT FROM AUTHOR]

This paper studies the structural parameters and electrophysical properties (dielectric and piezo electric, as well as currents of thermostimulated depolarization) of samples of composition 0.20BiScO3·0.45PbTiO3·0.35PbMg1/3Nb2/3O3 (or in short 0.20BS·0.45PT·0.35PMN) obtained by ceramic and melt-hardening methods of synthesis. In the ceramic method, the samples were obtained from the starting oxides by two-stage firing. In the melt method, amorphous precursors were first obtained from heat-treated and non-heat-treated starting oxide mixtures by melting and subsequent quenching under sharply gradient temperature conditions. Samples were obtained after grinding, pressing, and thermal annealing of the synthesized precursors, and four types of samples differing in size and shape of the intermediate precursor particles (crystallites) were obtained. The X-ray phase analysis showed that the predominant phase in the studied samples is the perovskite phase; in both types of samples, up to 5 wt.% of impurity phase with pyrochlore structure was also present. The samples of 0.20BS·0.45PT·0.35PMN exhibit dielectric properties characteristic of relaxor ferroelectrics, and the polarized samples exhibit a pronounced piezo effect with a piezo modulus value of d33~200 pC/N. A comparative analysis of the properties of the samples obtained by different methods has been carried out. The essential advantage of the melt method is that its use allows obtaining varieties of four kinds of ferroelectric relaxors and reduces the time of synthesis of samples by 2–3 times.

Piezocatalysis is capable of harnessing mechanical energy for environmental remediation, which is regarded as a green and promising technology to be exploited. Piezoceramics are struggling to be used as highly efficient piezocatalysts due to their grain size reaching tens of micrometers usually. Herein, a feasible and straightforward method is proposed to turn piezoceramic powders into highly efficient piezocatalysts by integrating size optimization and oxygen vacancy modulation. This strategy is validated by treating lead‐free Sr0.5Ba0.5Nb2O6 (SBN) piezoceramic powders with high‐energy ball‐milling (hBM). The rate constant k value of 46.95 × 10−3 min−1 for rhodamine B (RhB) piezocatalytic degradation of SBN‐hBM‐12h is almost 18 times higher than that of pristine SBN. Besides, the SBN‐hBM‐12 h catalyst performed superior antibacterial properties against Escherichia coli. The enhanced piezocatalytic efficiency is attributed to the introduced abundant oxygen vacancies absorbing and activating O2 into reactive oxygen species. Well‐modulated oxygen vacancy concentration can effectively accelerate the generation and separation of free carriers. However, the excess oxygen vacancies in SBN render the weakened piezoresponse thus suppressing the piezocatalytic activity. This study elucidates the critical role of oxygen vacancies in piezocatalysis and provides insights into the development of efficient piezocatalysts. [ABSTRACT FROM AUTHOR]

X-ray diffraction and dielectric studies were performed on synthesized ceramic samples of the section (1–x) (0.8PbMg[Formula: see text]Nb[Formula: see text]O[Formula: see text]BiScO3)⋅ x(0.8PbTiO[Formula: see text]BiScO3) with [Formula: see text]–1 of the ternary BiScO3–PbTiO3–PbMg[Formula: see text]Nb[Formula: see text]O3 (BS–PT–PMN) system, including the temperature dependence of thermally stimulated depolarization currents (TSDC). It was found that the samples are solid solutions with a perovskite structure, which have cubic symmetry in the range of x = 0–0.587 and tetragonal symmetry in the range of x = 0.680–1. In the intermediate composition range of x = 0.587–0.680 (morphotropic region — MR), the samples consist of a mixture of solid solutions of different symmetries. Data on the change in dielectric properties and TSDC(T) dependencies of solid solutions with a change in their composition were obtained. It was found that samples of compositions x =0–0.625 and 0.6875–1 exhibit relaxor-ferroelectric and conventional ferroelectric properties, respectively, while samples of compositions x = 0.625–0.6875 combine ferroelectric and relaxor-ferroelectric properties.

Low-consumption ceramics processing routes are expected to replace conventional ones due to environmental concerns. In this context, flash sintering is garnering interest because it allows dense ceramics to be obtained in just a few minutes and at relatively low temperatures. This is particularly interesting for sintering alkaline-based compounds due to the easy volatilization of these elements. In this work, current-controlled flash sintering is used to obtain potassium-sodium niobate (KNN)-based piezoceramics with refined microstructure and suitable stoichiometry, leading to improved functional properties. KNN-based materials are currently outstanding lead-free piezoceramics, with their properties highly sensitive to the proper construction of the polymorphic phase boundary, as in the case of the first promising composition (K 0.44 Na 0.52 Li 0.04)(Nb 0.86 Ta 0.10 Sb 0.04)O 3. Results of this work show that sintering parameters may determine the polymorphic behavior of this system, thereby evincing flash sintering allows polymorphic phase boundary to be fine-tuned. It is demonstrated that the convergence of microstructure refinement and compositional control holds the potential for enhancing properties through a proper electric current control during flash sintering. [ABSTRACT FROM AUTHOR]

Objectives. To examine the general principles and recent advances in the synthesis of high-purity and high-homogeneity barium titanate powders in the manufacture of electronic components.Results. The main publications regarding the synthesis of barium titanate powder, including the works of recent years, were analyzed. The technological advantages and disadvantages of various synthesis methods were identified. Groups of methods based on solid-state interaction of reagents and methods of “wet chemistry” were also considered. The possibilities of producing barium titanate particles of non-isometric shapes for creating textured ceramics were discussed separately.Conclusions. Barium titanate is a well-known ferroelectric with a high dielectric constant and low dielectric loss. It is used as a component in ceramic electronic products, for example, capacitors, memory devices, optoelectronic devices, and piezoelectric transducers. The possibilities of producing functional ceramics based on barium titanate powder largely depend on its state and morphological characteristics, determined during the synthesis stage. The most important factors affecting the functional characteristics of ceramics are the purity and morphology of the powder raw materials used.

Background. As of today in Russia there are no scientific-technical and experimental-technological reserves on development of systems of structural monitoring of serviceability of products and objects of rocket-space technology (RST) and ground space infrastructure (GSI) with transducers of physical quantities on the basis of macrofiber actuators on the basis of inverse piezo effect necessary for full assessment of reliability of technically complex objects by non-destructive methods. The development of the latest generation of aerospace structures requires the creation of advanced materials that would have high physical and mechanical parameters, meet reliability and durability requirements for specific tasks. Great importance is also given to active materials and structures capable of forming functional shapes and profiles depending on the external influence, i.e. to ensure the fulfillment of one of the principles of the motion control concept – adaptronics. The formation of functional shapes and profiles will provide optimal wing aerodynamic profile, better maneuverability of the aircraft, reduce fuel, energy consumption and provide better remote control in extreme space conditions. The purpose of this article is to create a scientific-technical and experimental-technological reserve for the development of advanced technologies for the production of sensor and actuator elements of structural performance monitoring systems based on piezoceramic materials and technologies for incorporation into the elements of composite structures of RST and GSI products in order to control and manage their characteristics to prevent emergencies. Materials and methods. The paper considers the structure of the system of structural monitoring of serviceability of products and objects of RST and GSI with transducers of physical quantities on the basis of macrofiber actuators based on the inverse piezo effect. Results. As a result of technology implementation, import-independent self-regulating adaptive structures of spacecraft structures and equipment will be created on the basis of controllable properties of materials with response to external influences. Implementation of the technology will make it possible to create an effective system for controlling vibrations of structural elements. The developed piezoactuators will find applications in structural monitoring systems of the aerospace industry in rocket and space technologies and mechanical engineering.

Ceramic samples with compositions along the (1 – 2x)BiScO3·(2 – y)xPbTiO3∙yxPbMg1/3Nb2/3O3 (y = 1.2, 1.0, 0.9, 0.5) sections in the BiScO3–PbTiO3–PbMg1/3Nb2/3O3 (BS–PT–PMN) system have been characterized by X-ray diffraction and dielectric, piezoelectric, and thermally stimulated depolarization current measurements. The materials with 1 – x ≲ 0.5 have been shown to consist of perovskite solid solutions. With increasing BS content, the symmetry of the solid solutions rises from tetragonal to cubic. In the intermediate composition region (morphotropic region (MR)), the samples consist of a mixture of solid solutions differing in symmetry. We have located the MR boundaries and examined the effect of composition on the dielectric and piezoelectric properties of the solid solutions. [ABSTRACT FROM AUTHOR]

Piezoelectric motors designed for operation in the ITER tokamak-reactor must be tested for stability under severe radiation conditions. Properties of lead zirconate-titanate that is the most common type of piezoelectric materials were analyzed from the point of view on influence of radiation. It is shown that, at the expected in ITER level of radiation, this piezoceramics has a good potential for resistance to radiation induced amorphization and depolarization. [ABSTRACT FROM AUTHOR]

The paper shows how different sintering methods affect the basic characteristics of PZT-type multicomponent ceramics. A perovskite-structured multicomponent ceramic of lead zirconate titanate (PZT) type doped with Mn4+, Sb3+, W6+, and Ni2+ and with a chemical composition of Pb(Zr 0.49 Ti 0.51) 0.94 Mn 0.015 Sb 0.01 W 0.015 Ni 0.03 O 3 was obtained. Ceramic powders were synthesized using the calcination method. Three sintering methods, including: (i) pressureless free sintering (FS), (ii) hot pressing (HP), and (iii) spark-plasma sintering (SPS), were used for the final sintering. The electrophysical measurements of the PZT-type ceramics, including scanning electron microscopy microstructure (SEM), X-ray diffraction (XRD), dielectric, ferroelectric, piezoelectric properties, and DC electrical conductivity, are presented. The microstructure of the samples is characterized by densely packed grains with correctly crystallized grain shapes but with different average grain sizes for each sintering technology used. At room temperature (RT), PZT ceramic samples have high values of resistivity ρ DC (from 7.25 × 108 Ωm to 1.14 × 109 Ωm), high values of permittivity (from 1048 to 1307), and low values of dielectric loss factor (from 0.008 to 0.02). Samples with the most favorable dielectric, ferroelectric, and electromechanical parameters were obtained using the FS and HP sintering methods. In the case of spark-plasma sintering (SPS), the assumed improvement in the electrophysical properties of the P-SPS ceramic sample was not obtained. Also, the most advantageous piezoelectric parameters have ceramic samples obtained by the FS and HP methods. The conducted tests verify that all the obtained ceramic compositions have a complete set of parameters suitable for micromechatronic applications. [ABSTRACT FROM AUTHOR]

This study demonstrates the impact of two sintering techniques on the fundamental properties of doped PZT-type ceramic materials (with Mn4+, Sb3+, Gd3+, and W6+), with the general chemical formula Pb(Zr0.49Ti0.51)0.94Mn0.021Sb0.016Gd0.012W0.012O3. The synthesis of ceramic powders was carried out through the calcination method. Two different methods were used in the final sintering process: (i) pressureless sintering (PS) and (ii) hot pressing (HP). The PZT-type ceramics were subjected to electrophysical measurements, encompassing various analyses such as X-ray diffraction (XRD), microstructure (scanning electron microscopy (SEM)), ferroelectric and dielectric properties, and DC electrical conductivity. The analysis of the crystal structure at room temperature showed that the material belongs to the perovskite structure from the tetragonal phase (P4mm space group) without foreign phases. Both sintering methods ensure obtaining the material with appropriate dielectric and ferroelectric parameters, and the tests carried out verified that the ceramic materials have a diverse range of parameters appropriate for use in micromechatronic and microelectronic applications. The obtained ceramic material has high permittivity values, low dielectric loss tangent values, and high resistance. At room temperature, the ceramic samples' P-E hysteresis loops do not saturate at a field of 3.5 kV/mm (Pm maximum polarization is in the range from 12.24 to 13.47 μC/cm2). However, at higher temperatures, the P-E hysteresis loops become highly saturated, and, at 110 °C, the Pm maximum polarization values are in the range from 28.02 to 30.83 μC/cm2. [ABSTRACT FROM AUTHOR]

Comparative studies of low-frequency dispersion, analysis of the most probable relaxation time and activation energy of the low-frequency relaxation process of sodium niobate ceramics obtained under various technological conditions for the synthesis of sodium niobate material were carried out. It is shown that the temperature conditions of the synthesis of the sodium niobate material determine the nature of the low-frequency dispersion only at relatively low temperatures (structural Q or P phase) of sodium niobate samples. [ABSTRACT FROM AUTHOR]

In this work, a new method for study of the process of domain orientations and space charge relaxation in ferroelectrics using the surface acoustic waves (SAW) has been developed. The results of an experimental study of the dc electric field influence on the parameters of SAW propagation in piezoceramics with different ferroelectric "hardness" are presented. [ABSTRACT FROM AUTHOR]

Ceramic materials of the Bi0.5Na0.5TiO3– xZnO (BNT – xZnO) system with the content of ZnO x = 0 and 2.0 wt.% obtained by the classical solid-state reaction method are studied. The initial powders (Bi2O3, TiO2 and Na2CO3) with a ZnO addition are milled for 10 h, calcined at 850°C for 3 h, pressed, and sintered at 1050°C for 3 h. The morphology and the microstructure of the sintered granules are studied using XRD, scanning electron microscopy, and a helium pycnometer. It is shown that the material acquires a solid solution of (Bi0.5Na0.5)TiO3 with a structure of pure perovskite and Zn2TiO4 spinel. The piezoelectric coefficient d33 after the sintering at 1050°C for the BNT ceramics amounts to 155 pC/N; in the case of BNT with 2 wt.% ZnO the value is 181 pC/N. The ZnO addition to the BNT ceramics raises the density of the material and provides an electrical conductivity of 7.48 × 108 Ω∙ cm. [ABSTRACT FROM AUTHOR]

The phenomenon of diffraction of laser radiation by particles of a damaged surface layer of a piezoceramic deposited on a plane-parallel glass plate was studied. A diffraction pattern is clearly observed in reflected and transmitted light, which is an alternation of light and dark concentric rings. These rings correspond to the conditions of diffraction maxima and minima. A bright spot is observed in the center of the diffraction pattern. The dependence of the radius of diffraction rings on the thickness of the glass plate was established. The diffraction angles at a given value of the order of maximum for different thicknesses of the glass plate were the same. The particles of the damaged surface layer of the piezoceramic, which scatter light, have different characteristic sizes. The study of particles using optical microscopy showed that their sizes are in the range of ~ (1 ÷ 3) μm. The shape of the grains is predominantly close to spherical. The Fraunhofer approximation was used to analyze the diffraction pattern. The distribution of the light intensity of the diffraction pattern depending on the diffraction angle has been analyzed. The simulation of the total scattered intensity as a function of the angle for particles with a diameter of 1.7 μm and 3.0 μm has been performed. The diffraction angles become smaller as the particle size increases. The distribution of the light flux in the diffraction pattern is constructed. This graph shows that most of the scattering intensity is concentrated near the center of the diffraction pattern, where the vast majority of the laser radiation falls. As the diffraction angle increases, the relative intensity of the maxima obeys the regularity 1 : 0.71 : 0.25 : 0.13. The size of the particles of the damaged surface layer of the piezoceramic was estimated using the laser diffraction method. The average particle diameter of the surface damaged layer of the piezoceramic is 1.7 μm. It can be argued that particles of such sizes make the main contribution to the creation of the diffraction pattern obtained by us under these experimental conditions. [ABSTRACT FROM AUTHOR]

Lead-free piezoceramics are gaining interest in the field of bone tissue engineering due to their surface charges and improved bone cell adhesion. However, monolithic materials are less suitable for more complex medical conditions, as the properties must be tailored and locally adaptable. Therefore, we designed a modular composite of ceramic building blocks and polymer-matrix to customize the piezoelectric properties with individual polarization of each block, while maintaining the benefits of each phase. Barium titanate building blocks were prepared by injection molding and were assembled into 2-2-layered and modular structures, which were bonded with barium titanate-filled (ΦP = 35 vol %) epoxy resin. The piezoelectric response was determined using direct excitation via Berlincourt method, and the influence of the matrix thickness as well as the different polarization orientations of individual building blocks was investigated.

Piezoelectric Vibration converters are nowadays gaining importance for supplying low-powered sensor nodes and wearable electronic devices. Energy management interfaces are thereby needed to ensure voltage compatibility between the harvester element and the electric load. To improve power extraction ability, resonant interfaces such as Parallel Synchronized Switch Harvesting on Inductor (P-SSHI) have been proposed. The main challenges for designing this type of energy management circuits are to realise self-powered solutions and increase the energy efficiency and adaptability of the interface for low-power operation modes corresponding to low frequencies and irregular vibration mechanical energy sources. In this work, a novel Self-Powered (SP P-SSHI) energy management circuit is proposed which is able to harvest energy from piezoelectric converters at low frequencies and irregular chock like footstep input excitations. It has a good power extraction ability and is adaptable for different storage capacitors and loads. As a proof of concept, a piezoelectric shoe insole with six integrated parallel piezoelectric sensors (PEts) was designed and implemented to validate the performance of the energy management interface circuit. Under a vibration excitation of 1 Hz corresponding to a (moderate walking speed), the maximum reached efficiency and power of the proposed interface is 83.02% and 3.6 mW respectively for the designed insole, a 10 k Ω resistive load and a 10 μF storage capacitor. The enhanced SP-PSSHI circuit was validated to charge a 10 μ F capacitor to 6 V in 3.94 s and a 1 mF capacitor to 3.2 V in 27.64 s. The proposed energy management interface has a cold start-up ability and was also validated to charge a (65 mAh, 3.1 V) maganese dioxide coin cell Lithium battery (ML 2032), demonstrating the ability of the proposed wearable piezoelectric energy harvesting system to provide an autonomous power supply for wearable wireless sensors. [ABSTRACT FROM AUTHOR]

This work was devoted to the first multi-parametric unitary comparative analysis of a selection of sintered piezoceramic materials synthesised by solid-state reactions, aiming to delineate the most promising biocompatible piezoelectric material, to be further implemented into macro-porous ceramic scaffolds fabricated by 3D printing technologies. The piezoceramics under scrutiny were: KNbO3, LiNbO3, LiTaO3, BaTiO3, Zr-doped BaTiO3, and the (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 solid solution (BCTZ). The XRD analysis revealed the high crystallinity of all sintered ceramics, while the best densification was achieved for the BaTiO3-based materials via conventional sintering. Conjunctively, BCTZ yielded the best combination of functional properties—piezoelectric response (in terms of longitudinal piezoelectric constant and planar electromechanical coupling factor) and mechanical and in vitro osteoblast cell compatibility. The selected piezoceramic was further used as a base material for the robocasting fabrication of 3D macro-porous scaffolds (porosity of ~50%), which yielded a promising compressive strength of ~20 MPa (higher than that of trabecular bone), excellent cell colonization capability, and noteworthy cytocompatibility in osteoblast cell cultures, analogous to the biological control. Thereby, good prospects for the possible development of a new generation of synthetic bone graft substitutes endowed with the piezoelectric effect as a stimulus for the enhancement of osteogenic capacity were settled. [ABSTRACT FROM AUTHOR]

This study demonstrates the impact of two sintering techniques on the fundamental properties of doped PZT-type ceramic materials (with Mn4+, Sb3+, Gd3+, and W6+), with the general chemical formula Pb(Zr0.49Ti0.51)0.94Mn0.021Sb0.016Gd0.012W0.012O3. The synthesis of ceramic powders was carried out through the calcination method. Two different methods were used in the final sintering process: (i) pressureless sintering (PS) and (ii) hot pressing (HP). The PZT-type ceramics were subjected to electrophysical measurements, encompassing various analyses such as X-ray diffraction (XRD), microstructure (scanning electron microscopy (SEM)), ferroelectric and dielectric properties, and DC electrical conductivity. The analysis of the crystal structure at room temperature showed that the material belongs to the perovskite structure from the tetragonal phase (P4mm space group) without foreign phases. Both sintering methods ensure obtaining the material with appropriate dielectric and ferroelectric parameters, and the tests carried out verified that the ceramic materials have a diverse range of parameters appropriate for use in micromechatronic and microelectronic applications. The obtained ceramic material has high permittivity values, low dielectric loss tangent values, and high resistance. At room temperature, the ceramic samples’ P-E hysteresis loops do not saturate at a field of 3.5 kV/mm (Pm maximum polarization is in the range from 12.24 to 13.47 μC/cm2). However, at higher temperatures, the P-E hysteresis loops become highly saturated, and, at 110 °C, the Pm maximum polarization values are in the range from 28.02 to 30.83 μC/cm2.

This paper presents a variational modeling framework for investigating the flexoelectricity-driven evolution of remanent polarization in piezoceramics. In small-scale electromechanical systems, strain gradients can exhibit polarization in dielectric materials via the direct flexoelectric effect. In ferroelectrics, it is reasonable to expect that a sufficiently large magnitude of the flexoelectricity leads to a switching of the domain structure and thus the material becomes remanently polarized. It is interesting to note that this means that poling would be able to occur in the absence of any external electrical source. This provides the motivation to gain a better understanding of this effect for a possible technical use in e.g. sensor applications. For this purpose, a macroscopic model is presented that couples flexoelectricity and ferroelectric domain switching processes. By embedding the model in the variational framework of the generalized standard materials (GSM), a minimum-type potential structure and thus a stable and efficient numerical treatment is obtained. A mixed finite element formulation based on the Helmholtz free energy is introduced to solve the higher-order flexoelectric boundary value problem. In order to realistically predict the flexoelectric material behavior, the model response is adapted to experimental results in literature obtained for a piezoceramic in a bending test. By simulations based on the adapted model the evolution of the flexoelectricity-driven remanent polarization in the vicinity of a notch is shown. • A variational modeling framework for flexoelectric problems is introduced. • A mixed finite element formulation based on Helmholtz free energy is used. • The model response is adapted to experimental results on the flexoelectric effect. • The flexoelectricity-driven remanent polarization in piezoceramics is investigated. [ABSTRACT FROM AUTHOR]

In high-power applications, since mechanical losses in piezoelectric devices always result in considerable heat generation, the temperature stability of the mechanical quality factor (Q m) is particularly crucial and should be considered in real piezoelectric applications. Here, we propose a poling-aging-repoling strategy to make the defect dipoles aligned with the poling direction as much as possible, thereby resulting in the strong pinning of ferroelectric domains. A giant internal bias field E i (11.6 kV cm−1 @ 1 Hz) and a high Q m (2074), accompanied by almost unchanged d 33 , are obtained in the composition of CuO-doped (K 0.48 Na 0.52) 0.94 Li 0.06 Nb 0.94 Ta 0.06 O 3 (KNNLT-Cu) ceramics with a diffused polymorphic phase transition. Furthermore, and this is more encouraging, the high electromechanical performance exhibits good temperature stability in the range from room temperature to 100 °C, suggesting that the thermal stability of Q m can be effectively improved by combining the strong pinning of defect dipoles with composition design and providing a way for the development and design of future high-power piezoelectric devices. By means of the poling-aging-repoling strategy. A giant internal bias field E i (11.6 kV cm−1 @ 1 Hz) and a high Q m (2074), accompanied by almost unchanged d 33 , are obtained in piezoceramic. [Display omitted] [ABSTRACT FROM AUTHOR]

The influence of static compressional stress on the anisotropy of piezoelectric ceramics of BaTiO3 and PZT types is considered theoretically and experimentally. Static compression changes the domain structure of piezoceramics. These changes occur due to the reorientation of mostly 90° domain axes. As a result, all the parameters of the material change—elastic, piezoelectric, and dielectric. Some of them increase, and some, on the contrary, decrease. Changes occur in a nonlinear way, and higher-order parameters appear. The relationship between the total volume of the reoriented domains and the change in elastic moduli and piezomoduli is theoretically considered. The corresponding theoretical dependences are obtained. To confirm these theoretical dependences, experimental measurements were performed using the ultrasonic pulse-interference method at a frequency of 8 MHz. There is practically no oscillation movement of domain boundaries at this frequency, therefore, the change in the system of elastic and piezoelectric moduli is structural, not dynamic. The possibility of predicting changes in the structure of modules as a result of static compression is shown. [ABSTRACT FROM AUTHOR]

One of the most promising candidates to replace lead-based compounds in actuator applications are Na 0.5 Bi 0.5 TiO 3 (NBT)-based materials. K 0.5 Na 0.5 NbO 3 (KNN)-modified NBT-BaTiO 3 (NBT-BT) solid solutions exhibit giant large-signal strain–electric-field coefficients (S max /E max) exceeding 500 pm V−1. However, despite the promising properties of the ceramics reported in the literature, the synthesis of these materials remains challenging, leaving gaps in the understanding of the synthesis-property relationship. In this contribution, we investigate the microstructure and the electrical properties while changing the composition to destabilize the ferroelectric order in the material, which is the key to achieve large strain response. Measurements of dielectric and ferroelectric properties reveal that Na- or Ti-deficiency or excess of Bi decrease the ferroelectric-to-relaxor transition temperature and remnant polarization, indicating a destabilization of the ferroelectric order. Additionally, the use of KNO 3 instead of K 2 CO 3 as the potassium source in KNN results in an additional destabilizing effect on the ferroelectric order, which can be attributed to better incorporation of K+ into the perovskite structure. The results identify the key aspects of the synthesis of NBT-BT-KNN ceramics to obtain high S max /E max values. [ABSTRACT FROM AUTHOR]

The Pb(Mg1/3Nb2/3)O3-based ceramic system was obtained by using a modified variant of the conventional ceramic method in order to get pyrochlore-free compositions. Solid solutions obtained from Pb(Mg1/3Nb2/3)O3 and Ln(Mg1/2Ti1/2)O3 with Ln = Y3+, La3+, Pr3+, Nd3+ and Sm3+, were synthesized using a 3-step columbite precursor method and appropriate milling and sintering conditions. The structural phases of all sintered compositions were investigated in detail. The X-ray diffraction results demonstrate that all the samples possess a perovskite structure. The influence of dopant on the incorporation degree in the solid solutions was studied. The dielectric constants at three frequencies were measured and the influence of the dopant on these values was discussed. [ABSTRACT FROM AUTHOR]

Objectives. Ferroelectrically hard piezoelectric ceramics are in demand for high-power applications in piezotransformers, ultrasonic emitters, and piezo motors, which requires a combination of high piezoelectric characteristics and mechanical quality factors in it. The aim of this research was to reveal the main regularities in the microstructure and functional characteristic formation of ferroelectrically hard piezoceramics based on two widespread chemical systems, Pb(ZrxTi1-x)O3 and (Na1-xKx)NbO3, through various technological modes of production. In this study, two fundamentally different technological ways of forming a dense microstructure on the example of above systems have been employed to obtain the best set of dielectric, piezoelectric, and mechanical parameters for practical applications. In the case of lead-containing ceramics, various sintering technologies have been used, including conventional ceramic, hot pressing, and spark plasma sintering.Methods. The microstructure of the piezoelectric ceramics was investigated using electron microscopy, and the functional characteristics were assessed in terms of mechanical and piezoelectric properties. The density values were determined by hydrostatic weighing in octane, the relative dielectric permittivity was measured using an LCR meter, and the values of the piezoelectric coefficient and mechanical quality factor were gathered using the resonance–antiresonance method.Results. This research has identified that spark plasma sintering technology makes it possible to obtain high-density samples, which contain a homogeneous microstructure and double the figure-of-merit values, for use in high-power piezoelectric devices that operate at piezoresonance frequencies. It also found that the addition of a small amount of CuNb2O6 (x = 0.025) to lead-free solid solutions leads to the formation of a liquid phase during sintering, thereby creating a compacted microstructure with relative density values (96%) that have practical limitations in conventional ceramic technology. An increase in both the piezoelectric and mechanical properties, which leads to a twofold increase in the values of the quality indicator, was also observed.Conclusions. It is possible to increase, and even to double, the functional characteristics of both lead-containing and lead-free ferroelectrically hard piezoceramics by varying the technology used in the manufacturing process. By using spark plasma sintering technology with lead-containing ceramics, it is possible to reduce the optimum sintering temperature by 200 °C and the sintering time by more than 20 times, thus reducing production costs.

In this work, electrophysical features of the hard ferroelectric material PKP-35 are studied in a wide temperature range. Research object is a solid solution of lead zirconate-titanate (PZT) modified with some additives prepared by the conventional solid-state sintering method. The temperature dependences of the dielectric permittivity and dielectric losses in weak fields at frequencies of 1, 10, and 1000 Hz are obtained. The dielectric hysteresis loops at different temperatures are studied, the material features are revealed, the scope of application is determined. [ABSTRACT FROM AUTHOR]

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Lead-free 0.69BiFe 1- x Ga x O 3 -0.31BaTiO 3 (x , 0–0.06) piezoceramics were synthesized via traditional sintering techniques. The phase structure, dielectric, piezoelectric and ferroelectric performances of the ceramics were studied systematically. The results revealed that all the samples locate near MPB of rhombohedral (R)-pseudocubic (pC) phase coexistence, and that Ga doping has distinct influences on the R/pC phase content ratio. An appropriate content of Ga doping favors densification and grains growth of the ceramics during sintering. With the increment of Ga content, the Curie temperature of the samples shifts towards lower temperature owing to increased tolerance factor t of the perovskites, and enhanced diffuse phase transition behavior was observed. In addition, both the piezoelectric and ferroelectric property are sensitive to the concentration of Ga doping. Significantly, the excellent piezoelectric coefficient d 33 up to 206 pC/N along with strong remanent polarization P r of 25 μC/cm2 are obtained in 0.69BiFe 0.985 Ga 0.015 O 3 -0.31BaTiO 3 materials which would be a promising substitute for the conventional lead zirconate titanate system ceramics. [ABSTRACT FROM AUTHOR]

The crystal structures and associated energy band structures of classic lead-based PZT (PbZr 0.5 Ti 0.5 O 3) and lead-free KNN (K 0.5 Na 0.5 NbO 3) piezoelectric ceramics prepared by a solid-state method are systematically studied based on the First-principles calculations. For better understanding relations between energy band structures and the phase structures in the PbZr 0.5 Ti 0.5 O 3 and KNN, the components PT (PbTiO 3)/PZ (PbZrO 3) and KN (KNbO 3)/NN (NaNbO 3) are also calculated. The results suggest that the vital contribution to R-T morphotropic phase boundary (MPB) in PbZr 0.5 Ti 0.5 O 3 comes from the hybridization of A-site and B-site ions, which causes stretching and tilting of oxygen octahedron and therefore leads to the formation of R and T phases. The KNN behaves differently. Moreover, it's concluded that the band structure highly inherited from tetragonal PbTiO 3 plays an important role in the construction of the R-T phase boundary according to the comparison of PbZr 0.5 Ti 0.5 O 3 and KNN. In general, the work inspires an idea from the view of energy band structure to realize R-T phase coexistence as well as improved piezoelectric properties in KNN-based lead-free piezoceramics. [ABSTRACT FROM AUTHOR]

The work is devoted to a numerical study of the behavior of vertically oriented eccentric (non-coaxial) electroelastic shells, containing a fluid in the gap between them. The solution of the problem is found in the framework of a three-dimensional formulation using the finite element method. The shells are made of the piezoelectric material polarized in the radial direction. Thin-walled structures are considered in the framework of the classical theory based on the Kirchhoff � Love hypotheses, as well as the equations of linear electroelasticity. The distribution of the electric potential through the thickness is assumed linear. The fluid is considered within the framework of a potential theory. The study of the low natural frequencies and vibration modes is carried out for different variants of the boundary conditions at the edges of the shells, the level of fluid in the gap and the eccentricity of the inner shell. The influence of the electric boundary conditions specified on the parts of the shells surfaces covered with electrodes is estimated.

Piezoelectric materials contain microstructural features (e.g., domain walls, interdomain spacing, and grain size) that span across several length scales, i.e., few nm in the case of interdomain wall spacing to several μm in case grain sizes. Recent experimental findings indicated that the domain configurations have more influence on the hardness of these materials than the grain size. In this study, nanoindentation experiments are conducted on polycrystalline PMN-PT (a relaxor ferroelectric material) with a focus to investigate the influence of domain configurations on the indentation size effect (ISE) in hardness, H. Different domain configurations are achieved by selectively annealing the as poled samples above and below the Curie temperature. Nanoindentation hardness is obtained in the load range of 1–5 mN with the maximum penetration depth well below the grain size of the samples. The experimental results reveal that all the samples, albeit to a different order, exhibit strong Reverse Indentation Size Effect (RISE) and normal ISE in H. The observed ISE is then analyzed using classical Meyer's law, the proportional specimen resistance (PSR) model and modified PSR (mPSR) model. The critical analysis of nanoindentation data reveals that the PSR model provides a satisfactory understanding of the genesis of RISE and ISE considering the elastic resistance of test material and frictional resistance at indenter facet/test material. [ABSTRACT FROM AUTHOR]

Electromechanical energy demands on homogenous thick films of piezoceramics with sufficiently large piezoelectric constant and reproducible performance. Single‐phase LiTaO3 films deposited by sol‐gel processing have been fabricated as cantilevers to investigate the interdependence of dielectric and piezoelectric properties as a function of film thickness. Phase pure LiTaO3 films with varying thickness in the range of 2.07‐4.37 µm on stainless steel substrates were obtained after calcination of samples at 650°C. The relative permittivity of optimized spin‐coated films peaked at 479.73 (1 kHz), whereas the piezoelectric coefficient (d33 mode) determined by piezoresponse force microscopy was in the range of 21‐24 pm/V. The effect of poling was studied through the butterfly and phase curves. A figure of merit (FOM) up to 3.29 (10−18 m2/V2) was determined for cantilever devices, which were able to generate a peak‐to‐peak voltage of 0.046‐0.15 V using a 1 MΩ resistor as an impedance load at a fixed acceleration of 1.5 m/s2. While the power density was in the range of ~4‐20 × 10−9 W/m3, which increased with the increasing film thickness. The leakage current density decreased in the range of 4 × 10−5‐6 × 10−7 A/m2 in the same direction. As both ferroelectric and piezoelectric properties of LiTaO3 films are dependent on film thickness, an optimal energy conversion efficiency was obtained for a thickness of ~3 µm. Furthermore, these devices were tested up to a temperature of 150°C for voltage generation. Given the need for lead‐free piezoelectric materials for environmental applications, these LiTaO3 cantilevers are very promising for vibrational energy harvester (VEH) applications especially due to their cost effectiveness, small size, stability at higher temperatures, and repeatable properties, which makes them suitable for MEMS devices for industrial applications. [ABSTRACT FROM AUTHOR]

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Piezoceramic materials provide the foundation for essential components of modern engineering applications in the fields of acoustics, sensorics, biomedical devices, and microelectronics. With device miniaturization, the industrial requirements for piezoceramics with complex geometries and improved efficiencies has grown tremendously. Traditionally manufactured piezoceramics demonstrate great piezoelectric properties but poor shape conformity. Additive manufacturing (AM) technologies, being a successful contender in the field of technical ceramics, makes its way into piezoceramics production. AM technology applied to traditional piezoelectric materials has many obstacles to overcome, since typical piezoceramic products require complex and intricate shapes, and often consist of composite materials. As a solution to these problems, AM technology can be transformed into a robust fabrication tool. This review intends to outline the current state of the art of AM technologies applied to the manufacture of piezoceramic materials. Modern piezoceramic materials are described in detail, including the effects of doping and texturing. The properties of piezoceramics and their composites are compared for traditionally and additively manufactured devices. The piezolectric properties of the materials produced using different manufacturing methods are summarized in comprehensive tables and figures, where the emerging trends in physical characteristics are revealed. The pros and cons of AM technologies are discussed, and the problems to be addressed in future work are highlighted. [ABSTRACT FROM AUTHOR]

Templated grain growth is beneficial for piezoelectric materials, the properties of which become the best in their single crystalline form. Nevertheless, a textured ceramic prepared by a templated grain growth technique often fails in exhibiting as good properties as expected in single crystals even with a high degree of orientation factor. Here, we propose a new strategy for maximizing texturing effect by suppressing the growth of untextured matrix grains. The textured ceramics made by our method, so-called bi-templated grain growth, are featured by ultrahigh piezoelectric properties (d 33 = ∼1,031 pC / N , d ⋅ g = ∼59,000, k p = ∼0.76). A special emphasis is on the achieved electric-field-induced strain of 0.13 % at 1 kV / mm , which is as high as that of single crystals. This work demonstrates that not only the degree of texture but also the coarsening of untextured matrix grains should be well-controlled to best exploit the templated grain growth technique. [ABSTRACT FROM AUTHOR]

The paper considers the problem of determining the effective properties of piezoceramics with metal inclusions. The homogenization problem was numerically solved in the representative volume with closed structure of inclusions. The effective moduli behavior was analyzed depending on the fraction of inclusions for piezoceramic PZT-5A with platinum inclusions. An increase in the effective stiffness moduli, the longitudinal and shear piezoelectric stress coefficients, and a considerable increase in the dielectric permittivities were discovered with the growth of the metal inclusions fraction. The effective dielectric permittivities grew for the same fraction of inclusions when the relative size of inclusions increased. [ABSTRACT FROM AUTHOR]

The intrinsic microstructural length scales of piezoelectric materials (e.g. grain size, nature of the domain and their orientations) spans from micron to nanoscale have a pronounced influence on the electromechanical behaviour. Of all these microstructural features, domain configurations particularly found to control the nanomechanical properties which can be tailored using domain engineering techniques. Keeping this in view, we investigated the effect of different domain configurations on the indentation size effects (ISE) in nanohardness of polycrystalline hard and soft lead zirconate titanate (PZT). The state of different domain configurations in hard and soft PZT is achieved by annealing the poled specimens slightly below and above the Curie temperature (Tc). Nanoindentation experiments at different indentation sizes are performed to evaluate the proposal of ISE. Further, the size-dependence in nanohardness is analyzed using the classical Meyer's law, the Hays-Kendall (H–K) model, the elastic recovery (ER) approach, the proportion specimen resistance (PSR) model and the modified PSR (MPSR) model. The results revealed that all the mechanistic models show excellent fitting of nanoindentation data and size-dependence in nanohardness is found to be sensitive to the domain configurations. The Meyer's law and H–K approach quantifies the ISE in both the PZT but do not provide any significant understandings about the origins of ISE. The PSR and MPSR models demonstrated that besides the domain configurations, size-dependence in nanohardness in piezoceramics could also be attributed to (i) material-dependent constants and (ii) surface artefacts. The true hardness values obtained from the ER, PSR and MPSR models are similar to each other due to the similar attributes in fitting the nanoindentation data. [ABSTRACT FROM AUTHOR]

Purpose. The purpose of the paper is to determine the influence of the geometric parameters of the stator of a linear piezoceramic motor in the form of a piezoceramic plate on the characteristics of its amplitude oscillations. Methodology. For the research, mathematical modeling in the COMSOL Multiphysics software package was used, taking into account the interrelation of electrostatic and mechanical phenomena. Results. By numerical simulation of the process of operating of a linear piezoceramic motor, a rational ratio of the width to the length of the piezoceramic plate is determined. Originality. The rational value of the thickness h of the piezoceramic plate of the motor is also established. Approximate dependencies are proposed for determining the parameters of the relationship between the geometric dimensions of the piezoceramic plate of a linear piezomotor, which makes it possible to predict its characteristics. The adequacy of calculation models is confirmed by experimental studies. Practical value. The results obtained can be used in the design of piezoceramic motors.

The recent review for the Restriction of Hazardous Substances Directive (RoHS) by the expert committee, appointed by the European Union, stated that the replacement of PZT “… may be scientifically and technologically practical to a certain degree …”, although replacement “… is scientifically and technically still impractical in the majority of applications.” Thus, two decades of sustained research and development may be approaching fruition, at first limited to a minority of applications. Therefore, it is of paramount importance to assess the viability of lead-free piezoceramics over a broad range of application-relevant properties. These are identified and discussed in turn: 1. Cost, 2. Reproducibility, 3. Mechanical and Thermal Properties, 4. Electrical Conductivity, and 5. Lifetime. It is suggested that the worldwide efforts into the development of lead-free piezoceramics now require a broader perspective to bring the work to the next stage of development by supporting implementation into real devices. Guidelines about pertinent research requirements into a wide range of secondary properties, measurement techniques, and salient literature are provided.