An investigation into the influence of electrically conductive particle size on electromechanical coupling and effective dielectric strain coefficients in three phase composite piezoelectric polymers

Three phase epoxy/piezoelectric/conductive filler composites were fabricated. The volume fraction of the conductive filler, aluminum, was held constant at 20%, while the volume fraction of the piezoelectric material, PZT was varied from 0.10 to 0.70. Three sets of composites were examined, wherein, the size of the aluminum constituent was varied from micron in size (200 mesh) to nano -in size (∼18 nm). Both sets of composites presented enhanced loss factor (tan δ) and piezoelectric coefficient (d33) values for volume fractions of PZT above 0.30 volume fraction. Composites having micron size aluminum particles exhibited higher loss factor and strain coefficients than those that incorporated nano-size aluminum particles, which could be due to several factors: agglomeration, contact resistance between particles, and excess air voids in the samples.