Piezoelectric properties of 3-Xperiodic Pb(ZrxTi1−x)O3–polymer composites

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Abstract
The piezoelectric properties of lead zirconate titanate (PZT)–polymer composites were studied as a function of composition and phase connectivity. PZT skeletal structures were fabricated by robotic deposition, densified at 1275 °C, and subsequently infiltrated with epoxy to produce the desired PZT–polymer composites. These 3-X structures consisted of a three-dimensional lattice of PZT rods (3–3) embedded in a polymer matrix, a PZT lattice/polymer matrix capped with PZT face plates (3–2), or PZT lattice/polymer matrix capped with PZT face plates and encircled by a solid PZT ring (3–1). The PZT:polymer ratio was varied systematically by changing the lattice (rod) spacing in each composite architecture. The concentration of PZT pillars, which formed along the poling direction at the intersections between PZT rods, varied as the PZT volume fraction squared. These 3-X composites displayed enhanced hydrostatic figures of merit relative to monolithic PZT due to stress concentration in the PZT pillars and their dramatically reduced dielectric constant, with the highest values found for the 3–2 and 3–1 composites. Our experimental observations were compared to theoretical predictions based on an isostrain, unit cell model modified to account for the partial support of stress in the stiff epoxy phase.