Functional behavior of ceramic multilayer actuators with inactive parts

Modern low-voltage piezoelectric actuators consist of a stack of thin ceramic layers with metallic electrodes in between. In this work the influence of the internal electrodes and other inactive parts on the piezoelectric charge constants is described in terms of a series model for the elastic properties. Both the longitudinal(d(33)) and the transversal(d(31)) charge constants are experimentally determined in multilayer actuators of 5 x 5 X 1 mm size, with active layers of 12-100 mu m thickness. and coverlayers of 0-200 mu m thickness. The series model is fitted to these data with only the materials' elastic constants as variables. Discrepancies can be qualitatively explained from diffusion of silver out of the Ag/Pd-electrodes. (C) 1999 Elsevier Science B.V. All rights reserved.