Experimental study of relaxations in unidirectional piezoelectric composites

This study investigated unidirectional piezoelectric composites made of lead zirconate titanate (PZT) ceramic fibres embedded in a polymeric matrix. Several samples with various amounts of PZT fibres were prepared and their dielectric spectra were measured in the frequency range 0.1-100 kHz and at temperature intervals from ambient to 210 degrees C. The interface plays a significant role on piezocomposite performances (such as stress transfer). The principal objective of this study is to highlight this interface by dielectric measurements for non polarized composites. For these piezocomposites, three relaxation processes were identified: the a mode relaxation associated with the glass transition of the epoxy resin matrix, the relaxation process associated with conductivity occurring because of the diffusion of charge carriers that was manifested for high temperatures above glass transition and low frequencies, and interfacial or Maxwell-Wagner-Sillars relaxation that is attributable to the accumulation of charges at the PZT fibres/epoxy resin interfaces. (C) 2005 Elsevier Ltd. All rights reserved.