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This study investigated the phase transition behavior and electrical properties of (K 0.5 Na 0.5)(Nb 1- x Zr x)O 3 (KNN‒100 x Z) and (K 0.5 Na 0.5)NbO 3 – y BaZrO 3 (KNN–100 y BZ) lead–free piezoelectric ceramics. The phase transitions in crystal structures were compared in KNN ceramics between single Zr4+ doping and Ba2+Zr4+ co−doping. Piezoelectric properties such as the piezoelectric constant (d 33) and electromechanical coupling factor (k p) are optimized for KNN‒6BZ ceramics and were clarified via the polymorphic phase transition from the orthorhombic to pseudocubic phase. The fitted degree of diffuseness (γ) for a phase transition from the modified Curie–Weiss law indicated that KNN ceramics as ferroelectrics are gradually transformed through BaZrO 3 modification. Accordingly, the enhanced strain properties at y = 0.08 consist of coexisting ferroelectric domains and polar nanoregions that are supported by ferroelectric–to–relaxor crossover in KNN‒100BZ ceramics. [ABSTRACT FROM AUTHOR]

The development and optimisation of piezoceramics are targeted usually to enhance their piezoelectric properties evaluated by both the direct or indirect measurement methods. The presented work aims to elaborate on the correlation of one direct (Berlincourt) and two indirect (convert and field-dependent) piezoelectric measurement methods on various material states. The role of the ceramic powder treatment by ball milling and electrophoretic deposition (EPD) technique on the determined electric properties as well as basic physical and mechanical properties of (Ba 0. 85 Ca 0.15) (Zr 0. 1 Ti 0.9)O 3 ceramics (BCZT) was investigated. It was found that the EPD technologically supported by milling allows obtaining thick and dense deposits (>2 mm). After sintering, the BCZT ceramics with a relative density of >95%, hardness in the range of 2.3–2.9 GPa and piezoelectric coefficients of d 33 * = 940 pm/V, d 33(E=0) = 427 pm/V and d 33 = 364 pC/N can be achieved. Reported results also suggest that indirect (field-dependent) and direct (Berlincourt) measurements of the piezoelectric coefficients can be comparable at optimal poling conditions. [ABSTRACT FROM AUTHOR]

The presence of a bluff body upstream of a cantilever beam promotes persistent, aero-elastic vibrations of the beam. Vortex-induced vibration in an array of two mutually interacting bluff bodies in such configurations undergoing two-degrees of freedom transverse oscillation has not been investigated before. In the present work, we have studied experimentally, the unsteady response of an array of two similar rigid cylinders, positioned side-by-side in reference to the freestream velocity, each one mounted on the upstream end of an elastic cantilever beam. By fitting the beams with piezoelectric layers, these configurations are converted to piezoelectric fluid energy harvesters (PFEH) that can extract small amounts of energy from the flow. Comparing the performance of linear (L-PFEH), non-linear (NL-PFEH), and a non-linear array (NLA-PFEH) of harvesters show that NLA-PFEH has the widest broadband operating velocity range and the greatest generated power followed by NL-PFEH and then L-PFEH. The maximum electric power output of NLA-PFEH was ~1000% greater than for NL-PFEH with a corresponding ~250% increase in the operating velocity range. Different cylinder configurations reveal the presence of hysteresis in the behavior of NLA-PFEH when the distance between the cylinders (so-called cylinder gap to diameter ratio), G / D < 0.5. At large distances from each other (G / D ≥ 4), the two cylinders behave like independent, isolated harvester units with rather weak mutual interaction. [ABSTRACT FROM AUTHOR]

This article presents an experimental investigation on the fretting wear behavior of piezoceramics P51, PSnN5, and PLiS51 against an Si3N4 ceramic ball under air condition. A sphere-on-flat contact pattern is used as the contact model. The influence of displacement amplitude, frequency, and normal force is taken into account. After each test, friction logs are used to determine the contact interface state. A 3D topography measurement instrument is applied to measure the surface morphology and wear volume. Fretting wear on piezoelectric ceramics under different normal loads, frequencies, and displacement amplitudes are summarized through the collection and analysis of experimental data. It is found that, among the three piezoceramics, PLiS51 has the best wear resistance at higher displacement amplitude and frequency and P51 has the best wear resistance at greater normal force. [ABSTRACT FROM AUTHOR]

An efficient long-term storage of cryogenic propellants is a challenge for future space exploration missions. The vapour bubbles formed as a result of boil-off in the tank walls can generate foam structures, which could be hazardous in different operations in orbit. A recently proposed approach to control the dynamics of bubbles is based on the generation of an acoustic field by means of a piezoelectric transducer. This technology needs to be validated at cryogenic temperatures in order to be applicable in space. In this perspective, different piezoelectric elements and matching layer materials have been tested at cryogenic temperatures to assess their performance at such environmental conditions. We consider the use of soft PZT piezoceramics coupled with an epoxy resin as the matching layer. Experimental data reveal that epoxy resin-based acoustic matching layers exhibit a linear increase in the transmittance of the acoustic amplitude at cryogenic conditions. The peak-to-peak amplitude increases as temperature decreases up to a factor of 1.6. This result opens the possibility of generating and transmitting acoustic waves at cryogenic temperatures, which could be used in the recently proposed technology to control the dynamics of vapour bubbles in cryogenic fuel tanks. [ABSTRACT FROM AUTHOR]

Shortening the period of bone repair based on BaTiO3/hydroxyapatite(HA) composites with osteoconductivity and osteoinductivity is important. However, when the piezoelectric properties of composites are matched with natural bone, the content of non-degradable BaTiO3 needs to reach 90%, which may not conducive to clinical application. The barium titanate content in the composite was reduced by doping Er3+ into the BaTiO3 of BaTiO3/HA composites with enhanced piezoelectric properties. The piezoelectric constant and compressive strength of composites increased with the increase of Er3+-doped barium titanate (BTEr) content. Appropriate piezoelectric stimulation can promote the growth of osteoblasts. 70% BTEr/30% HA is more beneficial to the proliferation of osteoblasts than 70% BaTiO3/30% HA. [ABSTRACT FROM AUTHOR]

Piezoelectric materials transform electrical energy to mechanical energy and vice-versa making them technologically important as actuators, sensors and transducers in wide ranging applications. New regulations on prevention of hazardous materials in industrial applications have led to a great surge in research on environment friendly alternatives of the commercial Pb-based piezoelectrics - Pb(Zr, Ti)O3. The field of lead-free piezoceramics has seen great advances in the last two decades. This review focuses on the current status of understanding of structure-property relationships in Na1/2Bi1/2TiO3-based lead-free polycrystalline piezoceramics. [ABSTRACT FROM AUTHOR]

Structure, microstructure, dielectric, and piezoelectric properties of PZT-based hard piezoceramics PCR-8 sintered by different methods were studied. It is shown that hot pressing and spark plasma sintering contribute to an increase in the ceramics density and improve their functional parameters, as well as lower sintering temperature. The optimal technological conditions for the mass manufacturing of the piezoceramics with enhanced dielectric and piezoelectric properties are determined. The obtained experimental results are discussed and the prospects for the application of the considered technological methods are outlined. [ABSTRACT FROM AUTHOR]

The article presents the results of research of the grains surfaces piezoelectric ceramics with ABO3 composition using scanning electron microscopy and atomic force microscopy. The dependences of the shape and size of the grains on the cation in position A are detected. Growth steps are observed on the surface of the grains. Domain walls on such grains are perpendicular to the growth steps. [ABSTRACT FROM AUTHOR]

The analysis of scientific publications for rotor systems on the elastic supports made it possible to develop a basic version of the design scheme of active elastic support with controlled quasi-zero stiffness based on adaptive piezoceramic elements. The main components of the mathematical model of the functioning of active elastic supports with controlled quasi-zero stiffness based on adaptive piezoceramic elements are substantiated, which will help create the foundations of a theory for solving the problem of effective vibration protection. Numerical results show the possibility of effective applying of the proposed solution to the problem of rotor vibration damping. [ABSTRACT FROM AUTHOR]

We discuss various methods for experimental determination of the complete set of constants for a polarized piezoceramic using a single ring-shaped specimen. A simulated calculation of the complete set of constants for PZT4 piezoceramic was performed in ANSYS, a finite-element software package. Additional data was obtained by measuring the second overtone of the radial vibrations in the ring. The constants were determined to within 1% or less. The study included the impact of Q-factor on measurements of the piezoceramic constant. We showed that when the piezoceramic constants are calculated via equation, the resonance frequencies must be determined using the peak complex admittance independent of the Q values. Experiments were performed using PKP-12 piezoceramic, and the piezoceramic coefficients were calculated for three standard piezoelement sizes using the resonance/antiresonance method, and for a single ring-shaped sample using the method developed in this paper. The results obtained using these different methods were found to be consistent. The thickness resonance was studied using a method specifically developed to measure this resonance. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics are used in wide-ranging applications as actuators, transducers, and sensors. For applications at ambient environmental conditions, it is desirable that the piezoelectric material exhibit large piezoelectric coefficient (d 33) and possess Curie point well above room temperature. Among the lead-free piezoelectrics, the classical ferroelectric BaTiO 3 exhibits Curie point and d 33 ∼ 120 °C and 190 pC/N, respectively. Most attempts at improving the d 33 of BaTiO 3 via chemical modifications significantly reduces the Curie point (T c). Here we show that it is possible to improve both the d 33 and T c of BaTiO 3. We found this possibility while investigating a solid solution of BaTiO 3 with BaAlO 2.5. An optimum composition, 0.97 BaTiO 3 -0.03BaAlO 2.5 of this solid solution exhibit d 33 ∼356 pC/N, Curie point 125 °C, and good thermal stability of the piezo response. [Display omitted] [ABSTRACT FROM AUTHOR]

The ternary 0.39Bi(Ni 1/2 Ti 1/2)O 3 –0.20PbZrO 3 –0.41PbTiO 3 :x(Bi 2 O 3 /PbO) [x = 0, 1, and 2 wt%] ceramics were synthesized via solid-state sintering technique. The impact of excess addition on structural and electrical properties was investigated. PXRD results confirmed the diffusion of excess addition in the 0.39Bi(Ni 1/2 Ti 1/2)O 3 –0.20PbZrO 3 –0.41PbTiO 3 (BNPZT) lattice, exhibiting the perovskite structure with major rhombohedral (R3c) and minor tetragonal (P4mm) phases. The microstructure of the samples exhibits average grain size distribution (<8 μm). The temperature and frequency-dependent dielectric measurement revealed the relaxor-like ferroelectric behaviour and curie temperature (T c ∼290 °C) observed in BNPZT:1 Pb ceramics. The improved remnant polarization (P r ∼ 23.47 μC/cm2) and coercive field (E c ∼16. 13 kV/cm) were obtained in BNPZT:2 Pb ceramics. The enhanced piezoelectric charge coefficient (d 33 ∼ 496 pC/N) and maximum strain (S max ∼0.12 %) were obtained for BNPZT. The least asymmetric factor (γ s) illustrates the lower concentration of inherent defects in BNPZT:1(Bi/Pb) ceramics. This study provides insight into microstructural and electrical properties tuning and paves the way for designing piezoelectric materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Polymer matrix composites with embedded ferroelectric and/or piezoelectric particles, constitute a novel and interesting class of engineering materials. The incorporation of ferroelectric and/or piezoelectric particles within a polymer matrix is expected to add functionality to the resulting composite, due to the variation of polarisation of the ceramic particles with temperature. In this work, an elastomeric matrix such as polydimethylsiloxane and BaTiO(3) nano and microparticles were used for the fabrication of composites at various concentrations and sizes of the reinforcing phase. Morphological and structural characteristics were investigated via scanning electron microscopy images and X-ray diffraction patterns. The dielectric behaviour of all fabricated specimens was investigated via broadband dielectric spectroscopy, in a wide frequency (10^−1 Hz–10 MHz) and temperature (30–200°C) range. In the dielectric spectra, two relaxation processes were detected, namely cold crystallisation and interfacial polarisation. Values of dielectric permittivity enhance with filler content, and particles’ size, while diminishes significantly with frequency. Finally, the ability of the prepared systems to store energy was examined by calculating their energy density. The higher energy-storing efficiency is exhibited by the micro-BaTiO(3) reinforced composites, while functional behaviour is induced via the thermally activated structural changes of ferroelectric particles.

The effect of a constant electric field (E) on the absorption of microwave electromagnetic energy (L) by BaTiO3 crystals and the highly sensitive PCR-1 piezoceramic was studied. The field dependence of the absorption value L(E) at the maximum of the spectrum L(f) has the form of a “butterfly”, and the dependence of the frequency shift of the maximum on the field strength f(E) has a hysteretic character. The PCR-1 L(f) absorption spectrum at high E is modulated by pulses in a wide frequency range. It is assumed that the cause of the amplitude–frequency modulation of the spectrum may be the electromagnetic radiation of incomplete local discharges at the surface of piezoceramics. The change in the magnitude and position of the resonance maximum in the absorption spectra and the appearance of amplitude–frequency modulation L(f) when exposed to a constant field is interpreted from the point of view of changes in the parameters and concentration of the domains walls, as well as the a- and c-domain wedges of mechanical twins resonating in the electromagnetic field.

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.

In this paper, we describe and present a Virtual Instrument, a tool that allows the determination of the electromechanical, dielectric, and elastic coefficients in polarised ferroelectric ceramic discs (piezoceramics) in the linear range, including all of the losses when the piezoceramics are vibrating in radial mode. There is no evidence in the recent scientific literature of any automatic system conceived and implemented as a Virtual Instrument based on an iterative algorithm issued as an alternative to solve the limitations of the ANSI IEEE 176 standard for the characterisation of piezoelectric coefficients of thin discs in resonant mode. The characterisation of these coefficients is needed for the design of ultrasonic sensors and generators. In 1995, two of the authors of this work, together with other authors, published an iterative procedure that allowed for the automatic determination of the complex constants for lossy piezoelectric materials in radial mode. As described in this work, the procedures involved in using a Virtual Instrument have been improved: the response time for the characterisation of a piezoelectric sample is shorter (approximately 5 s); the accuracy in measurement and, therefore, in the estimates of the coefficients has been increased; the calculation speed has been increased; an intuitive, simple, and friendly user interface has been designed, and tools have been provided for exporting and inspecting the measured and processed data. No Virtual Instrument has been found in the recent scientific literature that has improved on the iterative procedure designed in 1995. This Virtual Instrument is based on the measurement of a unique magnitude, the electrical admittance (Y = G + iB) in the frequency range of interest. After measuring the electrical admittance, estimates of the set of piezoelectric coefficients of the device are obtained. The programming language used in the construction of the Virtual Instrument is LabVIEW 2019®.

Solid state synthesis route was employed to form Ba0.85Ca0.15Zr0.1Ti0.9O3 powder. The calcined powder was high energy ball milled at different milling speeds to get powders of different particle sizes. XRD pattern of the ceramics made from these powders show the presence of pure perovskite. This paper deals with a systematic study of the pyroelectric and the fatigue properties of the ceramics. The room temperature pyroelectric coefficient (p) attains the minimum value p = 0.119X10−8 C cm−2K−1 for the ceramic made from the powder milled at 250 rpm. The fatigue was also found to be minimum for the same ceramic samples. [ABSTRACT FROM AUTHOR]

The effect of a constant electric field (E) on the absorption of microwave electromagnetic energy (L) by BaTiO3 crystals and the highly sensitive PCR-1 piezoceramic was studied. The field dependence of the absorption value L (E) at the maximum of the spectrum L (f) has the form of a "butterfly", and the dependence of the frequency shift of the maximum on the field strength f (E) has a hysteretic character. The PCR-1 L (f) absorption spectrum at high E is modulated by pulses in a wide frequency range. It is assumed that the cause of the amplitude–frequency modulation of the spectrum may be the electromagnetic radiation of incomplete local discharges at the surface of piezoceramics. The change in the magnitude and position of the resonance maximum in the absorption spectra and the appearance of amplitude–frequency modulation L (f) when exposed to a constant field is interpreted from the point of view of changes in the parameters and concentration of the domains walls, as well as the a - and c -domain wedges of mechanical twins resonating in the electromagnetic field. [ABSTRACT FROM AUTHOR]

Using the ANSYS finite element modeling software package, Russian and foreign methods for determining the constants (modules) of piezoceramics presented in regulatory documents are analyzed. A machine experiment was conducted in which the constants of piezoceramics are entered into a program where the boundary-value problem for an element of the selected size is solved and the resonant and antiresonance frequencies are determined numerically. A method for determining the complete set of ten compatible piezoceramic modules has been developed and theoretically justified. In the presented method, only one sample of piezoceramics in the form of a ring with various electrodes is involved. A scheme for determining the complete set of compatible constants of piezoceramics is described. The proposed method is based on the theoretical foundations of electrical engineering and the solution of electroelasticity problems. It is shown that the use of only one sample instead of four to determine the complete set of compatible constants of piezoceramics increases the accuracy of measuring elastic moduli, since there are no errors caused by the dispersion of the properties of samples of various shapes in sintering and polarization processes, and measurements are simplified. [ABSTRACT FROM AUTHOR]

The ferroelectric and piezoelectric properties of orthorhombic K 1- x Na x NbO 3 (KNN) piezoceramics with various Na concentrations x are studied by the first-principles calculations. The spontaneous polarization of KNN single crystals increases monotonically with Na concentrations, indicating an enhanced ferroelectricity in KNN. Moreover, the averaged shear, transverse and longitudinal piezoelectric coefficient d - 15 * , d - 31 * and d - 33 * of KNN piezoceramics are calculated from the data of KNN single crystals to show that piezoelectricity of KNN piezoceramics positively correlates with Na concentrations and exhibits the best performance at x = 0.5625, which agrees well with the available experimental data. At this concentration, d - 15 * , d - 31 * and d - 33 * of orthorhombic KNN piezoceramics reach maximum, which are 1.13, 1.79 and 0.85 times larger than those of KNbO 3 piezoceramics, respectively. This work provides a better understanding to the effect of Na concentrations on the enhanced ferroelectricity and piezoelectricity in the KNN piezoceramics. [ABSTRACT FROM AUTHOR]

Improving the operating characteristics of piezoelectric devices in high temperature environments urgently requires the development of piezoceramics with both high piezoelectric coefficient and excellent temperature stability. However, it is difficult for existing piezoceramics to take care of both at the same time. Generally, high piezoelectricity can be obtained at morphotropic phase boundary (MPB) in the binary systems, such as PbZrO 3 –PbTiO 3 and Pb(Mg 1/3 Nb 2/3)O 3 –PbTiO 3 , but the temperature stability is unsatisfactory, which seriously restricts the practical application. Here, an optimum composition having excellent comprehensive properties is constructed by designing multiple MPBs in the novel x Pb(In 1/2 Nb 1/2)O 3 - y BiScO 3 – z PbTiO 3 ternary system. When x = 0.04, y = 0.345 and z = 0.615, the specimen has a high piezoelectric coefficient d 33 of 478 pC/N at 200 °C, meanwhile, the fluctuation of d 33 is less than ± 10% over an ultra-broad temperature range of 50–350 °C. Combined with a variety of in situ analysis techniques, it can be determined that the temperature-insensitive high piezoelectric coefficient is related to the multiple MPBs design, which is beneficial to the optimization of the hierarchical domain configuration. The developed phase boundary design strategy paves a new way to building next generation high performance high temperature piezoceramics. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Improving the power generation characteristics of piezoelectric energy harvesters requires the construction of piezoelectric ceramics with high transduction coefficient (d33 × g33), which remains a big challenge. In this paper, guided by piezoelectric energy harvester applications, the relationship between the composition, microstructure and transduction coefficient of (1 − x)BiScO3–xPbTiO3 material is systematically studied. The results demonstrated that the sample with a composition of x = 0.64 not only has a high Curie temperature (426 °C) which is beneficial to improve the working stability of the device, but also has a very high d33 × g33 value (15,110 × 10−15 m2/N), which is significantly superior to the commercial PZT system. Excellent electrical performance can be attributed to the fact that the composition of x = 0.64 located near MPB has a very high piezoelectric charge constant (505 pC/N) at the same time with moderate dielectric constant (1907). The cantilever-type energy harvester made of optimized composition generated a high output power density of 2.93 μW/mm3 at room temperature, which charged a commercial 47 μF electrolytic capacitor to 22 V in just 220 s and lighted up 72 LEDs for 0.1~0.2 s. Further, x = 0.64 harvester exhibited a large output voltage of 2.76 V even at 350 °C, suggesting its potential use for powering high temperature wireless sensors. [ABSTRACT FROM AUTHOR]

Copyright of Mechanics & Advanced Technologies is the property of National Technical University of Ukraine KPI 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.)

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. [ABSTRACT FROM AUTHOR]

• Multi-layer ceramics with precise layer thickness control were successfully prepared by electrophoretic deposition (EPD). • Spark plasma sintering (SPS) significantly improved the durability of piezoceramic laminates. • The significant suppression of crack formation and chemical reaction at the layer interfaces was achieved. • Combining EPD and SPS is a promising concept for preparing multi-layer ceramics for energy harvesting applications. In this paper, the concept of multi-layer ceramics based on a combination of piezoelectric layers BaTiO 3 (BT) or (Ba 0.85 Ca 0.15)(Zr 0.1 Ti 0.9)O 3 (BCZT) alternated with mechanically durable ZrO 2 (Z) layers is investigated. Both BT/Z and BCZT/Z laminates were successfully electrophoretically deposited (EPD) due to knowledge of the deposition kinetics of individual materials and their green densities allowing precise layer thickness control. The EPD was followed by conventional sintering (CS) or spark plasma sintering (SPS). The CS resulted in the development of cracks, pores, and significant chemical reactions at the layers interfaces in both types of laminates. Laminates sintered by SPS were crack free with suppressed or none chemical reactions at the interfaces. The mechanical properties development across layers was monitored using nanoindentation. This approach identified interlayer porosity evolution and estimated the significance of the reaction zone at the interface. [ABSTRACT FROM AUTHOR]

For the sake of guarding the environment from the vital problems that results from the toxic effects of lead components, lead free (LKNN6-0.5%CeO2/polyester) piezoelectric composite are prepared in this work using cold press technique. Firstly, the lead free (LKNN6-0.5%CeO2) piezoceramics are prepared using normal sintering technique. The dielectric and piezoelectric properties of the composites were examined as a function of the volume fraction of ceramic particles, all composites showed well dispersion of the piezoceramic particles in the polyester matrix as shown in SEM images. The piezoelectric and dielectric coefficients were found to be improved as the concentration of ceramic particles increases. Although the procedure is simple, the composite prepared in this study exhibited better piezoelectric and dielectric constants with (d33=41 and Ԑr=157) at (80%) volume fraction.

Abnormal grain growth (AGG) is frequently observed in sintered (K, Na)NbO3 (KNN)‐based piezoceramics. However, in the present study, abnormal grain growth was unexpectedly discovered in calcined KNN‐based powders. To explain the phenomenon, three well‐established models that account for the AGG in sintered ceramics were discussed, including (a) liquid‐phase‐assisted grain growth, (b) two‐dimensional nucleation grain growth, and (c) complexion coexistence. However, the AGG in calcined powders was concluded to be none of them, but a consequence of the A‐site compositional inhomogeneity in the K2CO3Na2CO3‐Nb2O5 ternary system. Since repeated calcination and ball milling have low efficiency on solving AGG and the accompanied compositional inhomogeneity, abnormal grains were found to coexist with normal grains at a very high calcination temperature, that is, 1000°C. The compositional inhomogeneity is believed to be remaining even after sintering and consequently deteriorate the comprehensive performances, which might be a determinant for the unstable reproduction of KNN‐based piezoceramics. [ABSTRACT FROM AUTHOR]

The paper describes the results of the experimental study of the properties of piezoceramics, ceramic matrix composites "ceramics/crystal," and porous ceramics based on lead-free sodium-lithium niobates (Na, Li)NbO3 and sodium-potassium niobates (Na, K)NbO3 compositions. The measurements of elastic, dielectric and piezoelectric parameters, as well as microstructural studies of experimental samples of lead-free porous piezoelectric ceramics and composites were performed. It was shown that the use of alkali metal niobates in the form of ceramic matrix composites and porous ceramics allows to increase the main functional parameters of these materials and makes them competitive with piezoceramics of the PZT system. The developed lead-free porous and composite materials have a unique combination of parameters and can be used for the manufacture of ultrasonic transducers and devices for a wide range of applications, including medical and nondestructive testing equipment. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive study including computer 3D simulation, microstructural studies, and experimental measurements of different composites structures was carried out. The Wave 3000 finite differences software package was used for simulation. The results of simulation of longitudinal ultrasonic waves propagation in ceramics/crystal and ceramics/metal ceramic matrix composites are presented. Finite difference modeling made it possible to reveal the characteristic features of the propagation of longitudinal waves in inhomogeneous piezoelectrically active ceramic matrix composites. The simulation results were compared with the experimental data obtained by impedance spectroscopy and ultrasonic methods. Anomalies of complex elastic moduli near corresponding percolation thresholds and elastic dispersion regions were found out. [ABSTRACT FROM AUTHOR]

Copyright of Electrical Engineering & Electromechanics is the property of National Technical University, Kharkiv Polytechnic 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.)

A novel kind of 1-3 piezoelectric composite with modified polymer phase is designed and evaluated in this work. In order to reduce the influence of polymer phase on the vibration of piezoceramic pillars, the polymer phase is modified into a sandwich structure, in which epoxy resin is the middle layer and silicone rubber forms the upper and lower layers. Parameters such as resonance frequency, sound velocity, electromechanical coupling coefficient and characteristic impedance have been simulated by using finite element analysis software. Effects of these parameters are also simulated with different volume fractions of silicone rubber. Piezoelectric composites are fabricated and measured. Experimental results agree well with simulations. Measured electromechanical coupling coefficient shows an improvement of more than 11% over epoxy/ceramic 1-3 piezoelectric composites. [ABSTRACT FROM AUTHOR]

Lead-free lithium doped sodium potassium niobate piezoceramics having the compositional formula Na.47K.47Li.06NbO3 were synthesized by ceramic technique using high energy ball milling. The compounds were calcined at 850 °C for 3h and sintered at different temperatures viz. 900 °C, 950 °C, 1000 °C, 1050 °C and 1100 °C for 2h. The calcined compositions showed an orthorhombic perovskite phase and on sintering, the phase transformed to tetragonal phase and this tetragonal structure has been observed for sintering temperature up to 1050 °C. Effect of various sintering temperatures on the electrical properties like dielectric constant, dielectric loss and a.c. conductivity were also studied. The results obtained were analyzed and discussed in the paper. [ABSTRACT FROM AUTHOR]

Grain-size effect on functional properties of piezoceramics is nowadays an important topic due to the potential applications of these materials at the submicron scale. In this context, we explore the effect of the grain size reduction on the functional properties stability of piezoceramics. Submicron- and micro-structured Pb(Zr,Ti)O 3 -based materials are taken as model samples to carry out this study. Rayleigh analysis is used to quantitatively evaluate the domain wall contribution. The results show that the stability of properties depends strongly on grain size. Specifically, the nonlinear response decreases significantly when the grain size is reduced to the submicron scale. This behavior can be explained by taking into account that a grain size reduction involves a grain boundary increment, which may clamp domain walls. The results suggest that grain size engineering may be an effective alternative to the widely used compositional engineering in order to control the undesirable nonlinear behavior in piezoceramics. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Nano- & Electronic Physics is the property of Sumy State University 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.)

This paper describes a piezoelectric method for measuring the density and mass of ejecta from the free surface of a condensed material upon arrival of a shock wave at it and the use of this method at the Institute of Physics of Explosion (Institute of Experimental Physics of the Russian Federal Nuclear Center, Sarov). Piezoelectric sensor designs and methods of recording and signal processing are presented. Results of measuring the density and mass of ejecta using piezoelectric sensors, radiography, protonography, and the method of indicator foils are compared. [ABSTRACT FROM AUTHOR]

Ultimate properties of a porous ceramic is highly process dependent. In this study, prevalent porous ceramics fabrication methods (Freeze casting, Foam reticulation and Burnable Plastic Sphere (BURPS) method) have been compared by fabricating the porous lead zirconate titanate (PZT) based piezoelectric ceramics. Field emission scanning electron microscopy (FESEM) studies were performed to analyse the pore size and distribution of the ceramics. Hydrostatic co-efficients increased tremendously on incorporation of porosity which led to Hydrostatic Figure of Merit of 7480 in Foam reticulation samples (porosity 86 per cent). The three dimensionally interconnected networks in the freeze casted samples led to lowest acoustic impedance (6 MRayls) despite not having the lowest density. [ABSTRACT FROM AUTHOR]

The origin of the complex reflection splitting in potassium sodium niobate doped with lithium and manganese was investigated using temperature‐dependent high‐resolution X‐ray and neutron diffraction as well as electron probe microanalysis and scanning electron microscopy. Two structural models were developed from the diffraction data. A single‐phase monoclinic Pm model is known from the literature and is able to reproduce the diffraction patterns perfectly. However, a model with phase coexistence of two classical orthorhombic Amm2 phases can also reproduce the diffraction data with equal accuracy. Scanning electron microscopy in combination with electron probe microanalysis revealed segregation of the A‐site substituents potassium and sodium. This favours the model with phase coexistence and confirms the need for comprehensive analyses with complementary methods to cover a broad range of length scales as well as to assess both average and local structure. [ABSTRACT FROM AUTHOR]

Hexagonal plate-like potassium-sodium niobate (KNN) perovskite particles with average width of 5.8 µm, thickness of 0.5 µm, and high aspect ratio over 10 were successfully prepared via low temperature surfactant-free wet-chemical synthesis and subsequent calcination. Forming potassium rich hydrate particles was a crucial step for modulating the plate-like morphology with well-defined hexagonal outline and uniform size distribution, the aspect ratio of which increased with increasing potassium content. Removal of crystal water in the KNN-hydrate took place at 150–250 °C and the weight loss was approximately 9%. The K + /Na + ratio of the perovskite KNN plates obtained by calcination was consistent with the starting stoichiometry. This low-temperature wet-chemical synthesis route to KNN is expected to pave a low-cost scalable way for the mass production of plate-like template particles in the field of high-performance lead-free textured piezoceramics. [ABSTRACT FROM AUTHOR]

The quadratic electrostrictive effect possesses several unique advantages over the piezoelectric effect, including a fast response speed, temperature stability, hysteresis-free characteristic. In this regards, we report a 0–3 type 0.92(Bi .5 Na .5 )TiO 3 −0.06BaTiO 3 −0.02(K .5 Na .5 )NbO 3 :6 wt% Bi 4 Ti 3 O 12 (BNT-BT-KNN: BiT) composite ceramics to achieve the competent electrostrictive effect at room temperature. The electrostrictive behavior of composite ceramics was systematacially explored with respect to driving field, temperature, frequency and cycles. The manufactured composite ceramic is featured by not only large room-temperature electrostrictive coefficient Q 33 of 0.0327 m 4 C −2 but also superior thermal stability in the temperature range from 25 °C to 120 °C. Simultaneously, the gained electrostrictive response exhibited relatively good frequency-dependent and fatigue character. It is demonstrated that construct of a 0–3 type connectivity composite provides a highly effective path to tailor electrostrictive characteristic of BNT-based ceramics. The current study shows a significant advancement in the area of lead-free electrostrictive materials and can inspire potential interest in search for novel BNT-based ceramics with promising electrostrictive effect. [ABSTRACT FROM AUTHOR]

Constraining a piezoelectric material from freely expanding causes a reduction in capacitance. This reduction in capacitance has implications in energy harvesting, active vibration control, and ultrasonic sensing. This article investigates the reduction in capacitance when a thin piezoelectric disk is embedded in an isotropic host material. Both simplified (one-dimensional axisymmetric) and computational (finite element two-dimensional axisymmetric) analyses have been presented and used to calculate the expected reduction in capacitance of thin embedded piezoelectric disks for a number of ceramic-based piezoelectric materials. The analyses show that there is a non-linear relationship between the capacitance and the elastic modulus of the host material; with increasing host modulus, capacitance initially decreases rapidly but then asymptotically converges to the fully constrained case. A simplified equivalent spring axisymmetric model has been derived from the finite element model and has been used to explain some of the key geometric and material properties that effect the reduction in embedded capacitance. Preliminary experimental results show some agreement with the derived models; however, substantial further validation is required. Some implications of the derived results for energy harvesting are also discussed. [ABSTRACT FROM AUTHOR]

A steel strand is widely used in long span prestressed concrete bridges. The safety and stability of a steel strand are important issues during its operation period. A steel strand is usually subjected to various types of prestress loss which loosens the anchorage system, negatively impacting the stability of the structure and even leading to severe accidents. In this paper, the authors propose a wavelet packet analysis method to monitor the looseness of the wedge anchorage system by using stress wave-based active sensing. As a commonly used piezoceramic material, lead zirconate titanate (PZT) is employed with a strong piezoelectric effect. In the proposed active sensing approach, PZT patches are used as sensors and actuators to monitor the steel strand looseness. The anchorage system consists of the steel strand, wedges and barrel, which forms two different direct contact surfaces to monitor the tension force. PZT patches are pasted on the surface of each steel strand, corresponding wedge and barrel, respectively. Different combinations of PZTs are formed to monitor the anchoring state of the steel strand according to the position of the PZT patches. In this monitoring method of two contact surfaces, one PZT patch is used as an actuator to generate a stress wave and the other corresponding PZT patch is used as a sensor to detect the propagated waves through the wedge anchorage system. The function of these two PZTs were exchanged with the changing of transmission direction. The wavelet packet analysis method is utilized to analyze the transmitted signal between PZT patches through the steel strand anchorage system. Compared with the wavelet packet energy of received signals under different PZT combinations, it could be found that the wavelet packet energy increased with the increasing of anchorage system tightness. Therefore, the wavelet packet energy of received signal could be used to monitor the tightness of the steel strand during operation. Additionally, the wavelet packet energy of the received signals are different when the same PZT combination exchanges the energy transfer direction. With the comparison on the received signals of different combinations of PZTs, the optimal energy transfer path corresponding to different contact surfaces of the steel strand could be determined and the optimal experimental results are achieved.

Concrete is the most widely used material in civil engineering construction. Its life begins when the hydration process is activated after mixing the cement granulates with water. In this paper, a non-dimensional hydration parameter, obtained from piezoelectric ceramic (PZT) patches bonded to rebars embedded inside concrete, is employed to monitor the early age hydration of concrete. The non-dimensional hydration parameter is derived from the equivalent stiffness determined from the piezo-impedance transducers using the electro-mechanical impedance (EMI) technique. The focus of the study is to monitor the hydration process of cementitious materials commencing from the early hours and continue till 28 days using single non-dimensional parameter. The experimental results show that the proposed piezo-based non-dimensional hydration parameter is very effective in monitoring the early age hydration, as it has been derived from the refined structural impedance parameters, obtained by eliminating the PZT contribution, and using both the real and imaginary components of the admittance signature. [ABSTRACT FROM AUTHOR]

Compositions in the solid solution series (1-x)(Bi 0.5 Na 0.5 ) 0.935 Ba 0.065 Ti–x(LiSbO 3 ), (BNBT-LS) (x = 0, 0.01, 0.02, 0.03, 0.04) have been fabricated via solid state reaction route. Room temperature x-ray diffraction traces of all samples were found to reveal coexistence of the two structures; rhombohedral and tetragonal. The micrographs recorded from the Field Emission Scanning Electron Microscope, provided an overall dense and single phase microstructure for the systems. The dielectric anomalies corresponding to the maximum relative dielectric constant, ε r , persistently broadened and shifted to low temperatures as a function of increase in LiSbO 3 (LS) content. The ferroelectric P − E loops became steadily narrow with similar LS modification showing a continual decline in remnant polarization ( P r ) and coercive field ( E c ) . These phenomena clearly indicated the onset of a growing relaxor-like behavior. The maximum normalized unipolar strain S max / E max = d 33 * = 400 pm / V under the field 50 kV/cm was recorded for the system with x = 0.02. [ABSTRACT FROM AUTHOR]

The quality factor (Q) spectrum of a piezoceramic resonator, as a Q-factor frequency dependence for the specific resonator and its vibrational modes, was determined under baseline low-excitation level with a new approach proposed. The theoretical prediction was experimentally confirmed that the resonator Q-factor increases with frequency nearly linearly from the resonance reaching its maximum near the antiresonance. For the industrial PZT-5A piezoceramic the antiresonance-to-resonance quality factor ratio is 1.8 to 2.4 as much, depending on the type of vibration. As the theory states, this effect is directly related to the piezoelectric “losses” in piezoceramics, usually represented by the imaginary part of complex piezocoefficients, which have a unique property of lowering the total cumulative energy dissipation in a resonator in certain frequency intervals. Based on the electromechanical Q-factor (EMQ) concept, a new relatively simple method was proposed for the piezoelectric loss factor $\gamma $ determination at just a single resonance frequency—it requires measurements of the resonance Q-factor and its frequency derivative at the resonance, or the first and second frequency derivatives of the immittance phase at the resonance. Experimentally determined $\gamma $ is close to near 0.8 of its upper (positive) phenomenological limit in the conventional PZT-5A piezoceramic at the basic vibrational modes. The piezoelectric loss factor, theoretically reaching the upper limit, can provide extremely high value of the Q-factor (near the fundamental antiresonance) with possible an order of magnitude EMQ increase. That paradoxical fact for the piezoelectric “losses” is a novel possible way of improving the piezoceramic performance and operation. [ABSTRACT FROM PUBLISHER]