Electromechanical response of (3-0) porous piezoelectric materials: Effects of porosity shape

A three-dimensional finite element model is developed to accurately predict the complete electromechanical properties of porous piezoelectric materials with four geometric configurations of porosity, i.e., 3-0 type flat-cuboidal, 3-0 type spherical, 3-0 type short-cylindrical, and 3-1 type long-cylindrical porosity. The three-dimensional finite element model characterizes the complete electromechanical response of materials that belong to several symmetry classes, i.e., barium titanate (6mm), barium sodium niobate (mm2), and lithium niobate (3m). In general, the elastic, piezoelectric, and dielectric properties vary monotonically with increase in porosity volume fraction with the material properties in the longitudinal direction being the highest for the case of the materials with the 3-1 type long-cylindrical porosity for all three symmetry classes. The piezoelectric charge coefficient (d_h) and the hydrostatic figure of merit (d_hg_h) of the porous piezoelectric materials with the 3-0 type flat-cuboidal porosity are found to be significantly higher than those of the piezoelectric materials with spherical or short-cylindrical porosity. For example, in the barium titanate system, the differences in the d_h and d_hg_h values between the materials with the 3-0 type flat-cuboidal porosity and the materials with the 3-1 type long-cylindrical porosity are observed to be 223 and 1818 respectively, at 30 porosity volume fraction. Hence, piezoelectric materials with the 3-0 type flat-cuboidal porosity (that exhibit low aspect ratios with respect to the poling direction) could be better suited for hydrophone applications.