Piezoelectric materials are a key component in applications such as sensing, actuation and energy harvesting as they couple energy between the electrical and the mechanical domain. With increasing loads, the elastostriction and the electrostriction gain impact on the PZT transducer performance. A procedure to determine the nonlinear parameters is introduced and three different PZT ceramics are studied in comparison. The detailed investigation shows that the electrostriction is dominant in actuator applications, while the elastostriction is affecting sensor applications.
Piezoelectric constitutive equationsPiezoelectric materials feature the conversion of electrical energy into mechanical energy and vice versa. The electro-mechanical interactions are widely characterized by a linear stress-strain relation (1). Nevertheless, under higher loads the experimental values differ strongly from the linear model (2), mainly due to the increasing influence of elastostriction (3) and electrostriction (4). Different authors (5,6) have addressed the issue. The accuracy of these approaches is limited due to several simplifications. Further, (5) and (6) have determined two parameters from one experiment and did not consider the individual impact of each parameter. This paper gives a detailed characterization of the nonlinear parameters in bulk PZT ceramics and identifies their impact on applications for engineering, beyond the first approximation level.The volumetric electro-mechanical enthalpy H for a piezoelectric material can be written as equation [1]. U denotes the energy density, E n the electric field, and D n the electric displacement vector. n n E D U H − = [1]The state of strain ε ij is derived by the partial derivative of expression [1] with respect to the acting stress σ ij . Utilizing the free energy for a nonlinear electro-elastic material (7) and the dielectric displacement, equation [2] can be derived.