Mara S. Bernardo

Piezoelectric Elements for Multi-Element Linear-Array Transducers Prepared by Electrophoretic Deposition

Processing of piezoelectric linear-array elements for high-frequency linear-array transducers by electrophoretic deposition (EPD) was investigated. Powders with the nominal composition Pb (Zr0.53Ti0.47)0.98Nb0.02O3 (PZT Nb) and PbO were stabilised in ethanol by the addition of a polyelectrolyte and mixed together in a molar ratio 98:2. The suspensions of both powders consisted of particles with a median size of 0.2 μm and with a zeta potential of about-50 mV. They were deposited on alumina substrates with patterned gold electrodes at a constant current density. The deposits were sintered at 950°C in a PbO-rich atmosphere. The influence of the inter-electrode distance and the geometry of the counter electrode on the shape and dimensions of the thick films were studied. With the increasing inter-electrode distance the width of the elements decreased and the space between them (kerf) increased. A higher lateral resolution of the elements was obtained when using square-shaped counter-electrode compared to lined-shaped one. When depositing on a substrate with the electrode width of 1 mm and the kerf of 0.5 mm using an inter-electrode distance of 25 mm and a square counter electrode, 20 μm thick PZT Nb elements with a kerf of 360 μm and sharp edge were obtained. When the substrates with the electrode width and kerf of 150 μm were used, the 160 μm wide elements with a kerf of 144 μm were obtained at the same deposition conditions. The results demonstrated that EPD is a suitable technique to process aligned linear-array structures with an element width and a kerf in the order of a few tens of micrometres at optimised deposition conditions.