Theoretical Electroelastic Moduli of Porous Textured Piezoceramics

Nowadays, piezoceramics are commonly used in ultrasonic transducers (underwater applications, medical imaging, NDT …). Most of them are PZT-based materials (Pb(Zr, Ti)O3), which causes environmental issues due to the presence of lead. To comply with international regulations on the use of lead, numerous studies are conducted on lead-free piezoceramics (K0.5Nao.5Nb03, BaTiO 3 ) which can offer similar electromechanical performance to lead - based materials. Fabrication of lead-free textured ceramics enables the production of large area of piezoelectric materials with good electromechanical capabilities. Textured ceramics can be simply modeled as a 3-phases composite: one for the single-crystal that increases with the texturation degree, another one for the ceramic matrix and a last one for porosity. The amount of porosity depends on the sintering conditions. In the long wavelenght approximation, this material can be considered as homogeneous and characterized by effective properties. In this context, few studies were carried out for this homogeneization step and, in this paper, a homogeneization scheme is developped, based on the generalization of series and parallel connections. For the modeling, a unit cell is defined and used to determine the effective electroelastic moduli. Then, a validation step for this model is performed using FEM calculation. Results show that a high texturation is necessary and that the presence of porosity is not always damaging to optimize the targeted performance. Finally, theoretical properties of two single-element transducers based on textured piezoceramics are determined and compared to those based on PZT.