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This paper presents the results of an experimental study of the percolation behavior of the complex dielectric constant of ceramic matrix composites (CMC). Samples of piezoactive CMC were obtained by joint sintering of synthesized PZT piezoceramic powder (matrix) and crushed particles of sintered PZT piezoceramics (filler) of different compositions. The experimental dependencies of real and imaginary parts of the complex dielectric constant of CMC on the porosity of piezoceramic matrix and volume content of ceramic filler particles were measured and analyzed. It was shown that the additional porosity of the ceramic matrix resulting from sintering of the CMC masks the dielectric percolation transition, that actually occurs at the volume concentration of ceramic filler close to percolation threshold (V ∼ 1/3). [ABSTRACT FROM AUTHOR]

In this work, we studied the microstructure peculiarities and complex electromechanical parameters of porous piezoelectric ceramics based on the PZT system with different relative porosity and pore sizes. The complex elastic, dielectric, and electromechanical parameters of the porous piezoceramics were measured on the radial vibrational mode of standard samples and analyzed using piezoelectric resonance analysis (PRAP) software. It was revealed that the microstructural features of porous piezoceramics defined the character of the porosity dependences of real and imaginary parts of dielectric, piezoelectric, and electromechanical properties of porous piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

In the present study, particular aspects of the large-signal switching properties and electromechanical hysteresis of the lead zirconate titanate (PZT)-type porous piezoceramics were studied in comparison with the dense piezoceramics of the same composition. Large-signal ferroelectric polarization and strain hysteresis loops were recorded at the bipolar electric fields in the range of 0 ÷ 5 kV/mm and in the frequency range of 0.01 ÷ 5 Hz. Measurements and analysis were performed by means of the electromechanical measurement system (STEPHV) and electromechanical response characterization program (STEP), combining large-signal modeling of the mechanical and electrical behavior of ferroelectric materials. [ABSTRACT FROM AUTHOR]

In this work, the piezoelectric hysteresis and relaxation process induced by a weak DC electric field in ferroelectric ceramics were studied using the impedance spectroscopy method and piezoelectric resonance analysis program (PRAP). The DC field and time dependences of the complex dielectric constants were measured for the radial extensional mode of vibrations of thin piezoceramic disks. It was found that the hysteresis and relaxation nature of the field and time dependences of the complex dielectric constants were caused by the reversible displacements of 90° domain walls as well as the space charge transformation. [ABSTRACT FROM AUTHOR]

Results are presented from experiments on the dielectric hysteresis loops and relative dielectric permeability of 0.725NaNbO3–0.20KNbO3–0.075CdNb2O6 ceramics in strong (5–40 kV cm–1) and weak (0–0.3 kV cm–1) alternating electric fields. The parameters of reversible and irreversible constituents of contributions to the dielectric permeability are determined. A diagram of domain switching densities is plotted using the Preisach model. It is shown that the function of the domain distribution over local coercive fields is characterized by a sharp peak, testifying to the strong homogeneity of the domain structure. [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]

A digital material in the form of a composite consisting of particles of porous ferroelectric ceramics and a polymer matrix with the inclusion of metal particles was obtained. The properties of this material, as well as the properties of the polymer-metal matrix, were investigated. It is shown that this matrix has a high local conductivity. This provides electrical contact between the particles of porous piezoceramics, which is the main factor that ensures the presence of piezoelectric properties in this composite. [ABSTRACT FROM AUTHOR]

In the present work, we have developed a new method for the fabrication of piezoactive ceramic matrix composites (CMC) ceramics/ceramics. Samples of piezoactive PZT/PZT composites with a mass concentration of components from 0% to 60% have been obtained. A study of microstructural features, as well as a gravimetric analysis of CMC, has been carried out. It has been shown that the developed method for CMC manufacturing provides the formation of microhomogeneous composite structures with a uniform distribution of ceramic filler particles in a microporous piezoceramic matrix without the formation of transition regions and additional crystalline phases. [ABSTRACT FROM AUTHOR]

The aim of this work was to develop a new method alternative to high intensity focused ultrasound for spatial and temporal localization of ultrasonic heating effects using cylindrical standing waves. Computer simulations and experimental validation of the standing cylindrical waves generation and the viscoelastic media heating inside a cylindrical piezoelectric transducer were carried out. [ABSTRACT FROM AUTHOR]

In this work, we studied the piezoelectric hysteresis effect induced by a weak dc electric field in ferroelectric ceramics. Precision measurements of the impedance spectra for the thickness vibrational mode of thin piezoceramic disks at different polarities of applied dc electric field were performed using the method and program of piezoelectric resonance analysis (PRAP). The field dependences of the complex piezoelectric constants of piezoelectric ceramics obtained by processing successively measured impedance spectra were analyzed and a physical interpretation of the results was proposed. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive study of microstructure/properties interrelations for porous piezoceramics based on PZT composition was performed. Experimental samples of porous piezoceramics were fabricated using a modified method of burning-out a pore former. Porosity dependencies of elastic, dielectric, piezoelectric and electromechanical coefficients of the porous ceramics in the relative porosity range 0-50% were obtained and analyzed. As a result of microstructure analysis, it was found that at any connectivity type (3–0, 3–3) and porosity up to 50% the real structures of porous piezoceramics were close to the matrix medium structure with continuous piezoceramic skeleton. It was also revealed that the microstructural features of porous piezoceramics define the character of the dependences of the dielectric, piezoelectric and electromechanical properties of porous piezoelectric ceramics on porosity. In conclusion, microstructure/properties interrelations, as well as new applications of porous piezoceramics were discussed. [ABSTRACT FROM AUTHOR]

In this paper, the results of experimental study of dispersion characteristics of complex electromechanical parameters of ferroelectrically "hard" porous piezoceramics based on PZT composition were presented. Experimental samples of porous piezoceramics were fabricated using a modified method of burning-out a pore former. The complex constants of porous piezoceramics with relative porosity 16% and their frequency dependences were measured using the piezoelectric resonance analysis method. As a result of experimental studies, regions of elastic, piezoelectric and electromechanical dispersion, characterized by anomalies in the frequency dependences of the imaginary and real parts of the complex constants of porous piezoelectric ceramics were found. It was revealed also that the microstructural features of porous piezoceramics determine the character of frequency dependences of complex electromechanical parameters of porous piezoelectric ceramics. In conclusion, the microstructural and physical mechanisms of electromechanical losses and dispersion in porous piezoceramics were discussed. [ABSTRACT FROM AUTHOR]

The features of the crystal structure, microstructure and electromechanical properties of textured ferroelectric ceramics based on solid solutions of the Na0.5Bi4.5Ti4O15–PbNb0.5Cr0.5O3 system have been studied. Textured ceramics were manufactured by uniaxial hot pressing method with varying sintering conditions. The degree of crystallite orientation in samples with polarization direction perpendicular and parallel to the pressure axis during hot pressing was evaluated using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Complex elastic, dielectric, and piezoelectric parameters of textured piezoceramics were measured and analyzed using PRAP iterative automatic method. [ABSTRACT FROM AUTHOR]

This article presents the results of experimental study of the frequency dependences of complex electromechanical characteristics of layered ferroelectrics based on bismuth-containing compounds with a perovskite-like structure. Textured ceramics of the composition 0.9Na0.5Bi4.5Ti4O15-0.1PbNb0.5Cr0.5O3 were prepared by uniaxial hot pressing method with a special sintering conditions. Experimental disk-shaped samples were cut from the hot-pressed blocks and polarized parallel (E ǁ P) and perpendicular (E ⊥ Р) to the pressing axis (P). Complex electromechanical parameters of textured piezoceramics and their frequency dependences in the frequency range up to 50 MHz were measured and analyzed using PRAP iterative automatic method. [ABSTRACT FROM AUTHOR]

In this article, a correlation between microstructure and properties for porous piezoceramics of the composition Pb0.95Sr0.05Ti0.47Zr0.53O3 + 1% Nb2O5 was studied in detail. Experimental samples of porous piezoceramics were obtained using a modified method of burning-out a pore former. Porosity dependences of dielectric, elastic, piezoelectric, and electromechanical coefficients of the porous ceramics in the relative porosity range 0–50% were measured and analyzed. It was revealed that the microstructural features of porous piezoceramics defined the character of the porosity dependences of the dielectric, piezoelectric, and electromechanical properties of porous piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

An experimental study of the microstructural features and complex electromechanical parameters of lead-free ferroelectric ceramics based on solid solutions of the sodium-lithium niobate system was carried out. The phase distribution, as well as grain and domain structure were studied by piezoresponse force microscopy and scanning electron microscopy. A complete set of complex elastic, dielectric, and piezoelectric parameters of lead-free ferroelectric ceramics Na0.87Li0.13Sr0.01Nb0.99O3 + 1 at.% SiO2 was measured and analyzed using the Piezoelectric Resonance Analysis Program automatic iterative method. The frequency dependences of complex electromechanical parameters of the samples were measured in the frequency range up to 90 MHz. [ABSTRACT FROM AUTHOR]

Composites of a mixed type, consisting of porous piezoceramics particles in a polymer matrix, were produced and studied. A fabrication technique of such composites with 0–3 and 1–3 connectivities suitable for 3D printing method was presented. Their dielectric, electromechanical, and piezoelectric characteristics were measured. Dependences of dielectric permittivity on the number of layers of piezoceramic particles in the composite sample and on the ratio between the particle size and piezoelement thickness were presented. Single layer composites with appropriate ratio of the sample thickness and piezoelectric particles diameter demonstrated piezoelectric and electromechanical properties close to those of the initial piezomaterials. [ABSTRACT FROM AUTHOR]

An experimental study of the origin of elastic, dielectric, and piezoelectric losses in ceramic-matrix piezocomposites PZT/α-Al2O3 with different volume concentrations and particle sizes of α-Al2O3 microcrystalline filler was performed. The microstructural features and concentration dependences of the imaginary and real parts of the complex elastic, dielectric, and piezoelectric characteristics of composite piezoelectric elements were studied. The analysis of the obtained dependences was carried out and a physical interpretation of the obtained results was proposed. [ABSTRACT FROM AUTHOR]

The paper studies domain orientation processes in ferroelectric ceramics induced by a weak dc electric field. The field dependences of the complex elastic, electromechanical, and piezoelectric parameters of the PZT type ferroelectric ceramics were measured using the piezoelectric resonance analysis method for the radial extensional mode of thin piezoceramic disks. The method used ensures high accuracy in determining the complex constants of piezoelectric materials, as well as their changes under external influences. A physical interpretation of the results is proposed. [ABSTRACT FROM AUTHOR]

We studied the transient and relaxation processes occurring in ferroelectric ceramics under the influence of dc electric field. Precision measurements of the impedance spectra of ferroelectric ceramics of the PZT system at different values and polarities of applied dc electric field were performed using the method and program of piezoelectric resonance analysis (PRAP) for the radial vibration mode of thin piezoceramic disks. The time dependences of the complex piezoelectric parameters of piezoceramic elements obtained as a result of processing of successively measured impedance spectrta were analyzed and a physical interpretation of the results has been proposed. [ABSTRACT FROM AUTHOR]

The electromechanical properties and microstructural features of ceramic-matrix piezocomposites PZT/α-Al2O3 with different volume fractions of microcrystalline α-Al2O3 filler were studied. The concentration dependences of the complex elastic and electromechanical parameters of piezoelectric elements on α-Al2O3 microcrystals concentration were measured. It was found that, along with the influence of the non-piezoelectric phase α-Al2O3, the microporosity of the piezoceramic matrix appearing during sintering plays a decisive role in the formation of the electro-physical properties of ceramic-matrix piezocomposites PZT/α-Al2O3. [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]

A method for fabrication of piezomaterials based on the ferroelectric ceramics - polymer composites in the form of multilayer structures was developed. Samples of these materials were obtained and their electromechanical properties, as well as the dependences of these properties on the number of layers in multilayer structures, were studied. [ABSTRACT FROM AUTHOR]

In this work, we studied elastic and electromechanical characteristics and microstructural features of piezoactive ceramic-matrix composites PZT/LiNbO3 with a volume fraction of microcrystalline LiNbO3 filler from 0 to 15 vol. %. The dependences of the complex elastic and electromechanical parameters of composite piezoelectric elements on LiNbO3 microcrystals concentration were measured. It was found that in the formation of the electrophysical properties of ceramic-matrix composites PZT/LiNbO3, the microporosity of the piezoceramic matrix appearing during the composite sintering played a decisive role. [ABSTRACT FROM AUTHOR]

In this work, complex studies of the elastic dispersion and losses in porous piezoceramics based on solid solutions of the PZT system were carried out. Full set of complex constants of porous ceramics with different porosity and their frequency dependences were measured using the piezoelectric resonance analysis method.The microstructural and physical mechanisms of elastic losses and dispersion in porous piezoceramics were considered. [ABSTRACT FROM AUTHOR]

Method of digital piezomaterials fabrication based on mixed composites of the "piezoelectric ceramics-polymer" system is presented. The materials intend for use as precursors in the manufacture of piezoelectric elements using the technology of layer-by-layer bonding of powders. The method of investigation of these materials and frequency dependences of their electromechanical properties is described. [ABSTRACT FROM AUTHOR]

In this work, the frequency dependences of complex piezoelectric, dielectric, and elastic parameters of lead-free ferroelectric ceramics based on solid solutions of the (Na, Li)NbO3 system were studied in the frequency range up to 100 MHz. A complete set of complex parameters of lead-free ferroelectric ceramics was measured using the PRAP automatic iterative method. It was shown that the studied lead-free ferroelectric ceramics are characterized by low attenuation of ultrasonic waves and lack of dispersion in a wide frequency range, and can be used in high-frequency ultrasonic transducers for medical and nondestructive testing equipment. [ABSTRACT FROM AUTHOR]