Dielectric and piezoelectric properties of percolative three-phase piezoelectric polymer composites

Abstract

Three-phase piezoelectric bulk composites were fabricated using a mix and cast method. The composites were comprised of lead zirconate titanate (PZT), aluminum (Al), and an epoxy matrix. The volume fraction of the PZT and Al was varied from 0.1 to 0.3 and 0.0 to 0.17, respectively. The influences of an electrically conductive filler (Al), polarization process (contact and Corona), and Al surface treatment, on piezoelectric and dielectric properties, were observed. The piezoelectric strain coefficient, d33, effective dielectric constant, εr, capacitance, C, and resistivity were measured and compared according to polarization process, the volume fraction of constituent phases, and Al surface treatment. The maximum values of d33 were ∼3.475 and ∼1.0 pC/N for corona and contact poled samples, respectively, for samples with volume fractions of 0.40 and 0.13 of PZT and Al (surface treated), respectively. Also, the maximum dielectric constant for the surface treated Al samples was ∼411 for volume fractions of 0.40 and 0.13 for PZT and Al, respectively. The percolation threshold was observed to occur at an aluminum volume fraction of 0.13. The composites achieved a percolated state for Al volume fractions >0.13 for both contact and corona poled samples. In addition, a comparative time study was conducted to examine the influence of surface treatment processing time of aluminum particles. The effectiveness of the surface treatment, sample morphology and composition was observed with the aid of scanning electron microscope and energy dispersive x-ray spectroscopy images. These images were correlated with piezoelectric and dielectric properties.