Lead–Zirconate–Titanate Thick Films by Electrophoretic Deposition for High‐Frequency Ultrasound Transducers

Lead–zirconate–titanate (PZT) thick films for high-frequency ultrasound applications were fabricated using an electrophoretic deposition (EPD) process. The PZT powder was synthesized from constituent oxides at close-to-room temperature by mechanochemical activation followed by calcination at 700°C. Homogeneous PZT thick films with a thickness of ~30 μm and a density of ~80% were produced from ethanol-based colloidal suspensions containing PZT and PbO particles that were deposited using a constant-current mode on a platinized alumina substrate and were sintered in the presence of a liquid phase at temperatures compatible with thick-film technology. The dielectric, mechanical, and piezoelectric parameters of the PZT thick films with a porosity of ~20% were measured and a thickness-coupling factor of 48% was obtained. Considering that a PZT thick film is a composite structure consisting of PZT and pores, there are several methods that can be applied to calculate the effective parameters where the composite is considered as a piezoelectric homogeneous material. For this study, a matrix method based on a generalization of 2-2 connectivity was used to deduce the parameters of a completely dense configuration. Our results confirmed that the EPD process is suitable for the fabrication of efficient, high-frequency transducers operating at frequencies above 40 MHz.