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.