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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]