Evaluation of the effect of porosity and substrate on the piezoelectric behaviour of thick-film PZT elements

Abstract

This work presents a method to establish the elastic and piezoelectric constants of a thick film screen printed PZT composite over an alumina substrate. The calculus procedure uses as input data the parameters from the bulk material because it is basically the same component of which the thick film paste is manufactured. We also need to know frequencies of resonance and anti-resonance as well as the permittivity and density of the film in a poled disc sample. This method takes into account three factors: the additional components such as the glass frit, porosity of the film caused by the low temperature sinter process and the film clamping to the substrate. Each one of these factors reduces the piezoelectric efficiency by a different amount and, consequently, the measured values of the constants. The results obtained in this way are compared with experimental measurements of the effective piezoelectric charge constant d33 and permittivity with good agreement. Small discrepancies could be explained mainly due to lack of homogeneity in glass as well as in pore distribution.

One-step firing for electroded PZT thick films applied to MEMS

“…The thickness vibration modes in the MHz range are observed for both released and clamped samples, whereas the in-plane vibration mode is only activated when the PZT device is released from the substrate. This is in agreement with previous results and models [33,34]. Concerning in-plane vibration modes, larger dimensions induce lower resonance frequencies.…”