Effective Electromechanical Properties Research Articles

Piezoelectric Activity and Sensitivity of Novel Composites Based on Barium Titanate-Hydroxyapatite Composite Ceramics

This paper describes the effective electromechanical properties of hydroxyapatite-BaTiO3 0-3 composites as a potential bone substitute material. The permittivity, d3j and g3j piezoelectric coefficients are calculated for composites at a range of compositions and connectivities to understand the relationships between composite composition and piezoelectric and dielectric properties. The properties of the composites can be tailored by adjusting the volume fraction and aspect ratio of the BaTiO3 particles and the shape and level of porosity in the hydroxyapatite matrix.

A hierarchy of inclusions and electromechanical properties of 0–3 ceramic/polymer composites

This paper is devoted to the study of effective electromechanical properties of piezoactive 0–3 composites based on perovskite-type ferroelectric ceramics. A new model of the 0–3 ceramic/polymer composite is proposed for prediction of the effective properties. This model and the related averaging procedure are concerned with taking into account a hierarchy of inclusions in the polymer matrix and an electromechanical interaction among components. Numerical results are presented for the Pb(Zr, Ti)O3- and (Pb, Ca)TiO3-based composites to show the effect of different inclusions on the dielectric and piezoelectric properties. It is also shown that analytical predictions of the effective properties of the studied 0–3 composites are in good agreement with existing experimental data in wide concentration ranges.

Effective electromechanical properties of transversely isotropic piezoelectric ceramics with microvoids

In most piezoelectric materials and smart structures, the presence of microvoids can hardly be avoided. In the present paper, detailed three-dimensional (3-D) finite element analyses based on the unit cell method are carried out to investigate the inherent relations between the effective properties and the non-uniform distributions of microscopic electromechanical coupling fields resulting from microvoids. The emphases are placed on the influences of void volume fraction, void distribution, void shape and configuration on the effective properties of voided piezoelectric ceramics. The influences rooting in the permeability of voids and piezoelectricity of matrix materials on the effective properties of voided piezoelectric ceramics are also studied. The results obtained by this study have prospective guiding significances to the structural integrity analyses and fabrication of piezoelectric ceramics.

Effective electromechanical properties of ferroelectric piezoactive composites of the crystal-ceramic type based on (Pb1−x Cax)TiO3

Based on the previously proposed models, effective electromechanical properties of the ferroelectric piezoactive composites of the “single-domain crystal-ceramic” and “polydomain crystal-ceramic” types are determined for the first time. Features of the concentration dependence of the piezoelectric coefficients of four types (e3j*, d3j*, g3j*, and h3j*) are interpreted. Advantages of the new composites in comparison with the known ferroelectric piezoceramic materials of the PbTiO3 type are considered and explained. It is shown that the coefficients e3j* are most sensitive to a change in the system parameters; some reasons for this sensitivity are established.

Features of electromechanical properties of piezoactive compositeswith elements of connectivity 1-1

Effective electromechanical properties, figures of merit andrelated parameters are firstly studied within the framework of proposedmodels of piezoactive composites `ferroelectric ceramic-polymer'(connectivity 1-1) and `ferroelectric ceramic-porous polymer'(connectivity 1-0-1). The effect of the shape of the pores on the piezoelectriccoefficients, their anisotropy, electromechanical coupling factors, figures of merit,etc in 1-0-1 composites is analysed. The calculatedconcentration dependences of the piezoelectric coefficients and otherparameters as well as the piezoelectric anisotropy of 1-1 and 1-0-1composites have no analogy to known data on two- and three-componentcomposites on the basis of ferroelectric ceramics.

Electromechanical Properties of Porous Piezoelectric Ceramics

A theoretical approach is forwarded to predict the electromechanical properties of porous piezoelectric ceramics. The analysis is able to account for the effects of porosity shape and concentration and is applicable to piezoelectric ceramics of arbitrary material symmetry. By coupling the exact solution for a single ellipsoidal pore embedded in an infinite piezoelectric matrix with an effective medium approximation, the theory considers, in an approximate manner, interaction effects at finite porosity concentrations. The theoretical estimates are developed using a matrix formulation which enables all elastic, dielectric, and piezoelectric moduli of the porous solid to be readily computed. Numerical results are presented to illustrate the effects of the shape and concentration of the porosity on the effective electroelastic moduli and transducer parameters of practical importance. Particular attention is devoted to assessing the sensitivity of the effective electromechanical properties to the accuracy of the input data. Finally, theoretical estimates are shown to be in good agreement with existing experimental results for porous piezoelectric ceramics with various microstructural geometries.