Directed Colloidal Assembly and Characterization of PZT -Polymer Composites

Abstract

Concentrated (&phis;PZT = 0.47) PZT-5H gels were developed as inks for the robotic deposition of 3-D, mesoscale periodic structures with self-supporting features such as lattices of rod-like elements and v-shaped test structures. The gels exhibited pH dependent viscoelastic properties and Hershel-Bulkley flow behavior. The deflection of as-deposited spanning elements was measured using laser profilometry. Flow modeling and shape evolution data indicated a core-shell architecture as the ink exited the deposition nozzle, which simultaneously provided strength to form spanning elements and good bonding between layers. The core grew rapidly (∼1s) due to the quick recovery of gel structure in these inks. 3-X type PZT-polymer composites consisting of PZT lattices in a polymer matrix (3-3), a lattice/polymer matrix with PZT faceplates (3-2), or a lattice/polymer matrix with faceplates and encircled by a solid PZT ring (3-1) were formed and their piezoelectric properties were characterized. The PZT:polymer ratio was controlled by the lattice spacing in these thin composites (∼1 mm). Lattice rod intersections formed high permittivity, low compliance PZT pillars that concentrated stress and electric flux, leading to improved hydrostatic figures of merit.