Electromechanical response of porous piezoelectric materials

A finite element model is developed to study the effects of porosity on the electromechanical response of piezoelectric materials. Upon classifying 3-1-type porous materials as "longitudinally" or "transversely" porous, depending on the relative orientation of the porosity axis with respect to the poling direction of the piezoelectric material, the effects of porosity on the coupled properties of piezoelectric materials are systematically characterized. It is demonstrated that: (i) "longitudinally" porous materials with circular porosity cross-section exhibit higher order symmetry while "transversely" porous materials with elliptical porosity cross-section display lower order symmetry; (ii) the principal elastic, dielectric, and piezoelectric properties decrease monotonically with an increase in the porosity volume fraction (with higher sensitivity to porosity geometry in "transversely" porous materials); (iii) increasing the porosity in a piezoelectric material (especially in the "transverse" sense) enhances the utility of the materials for select applications by decreasing the acoustic impedance and increasing the hydrostatic charge coefficient.