  We have studied the processing of piezoelectric thick films using
electrophoretic deposition (EPD) for high-frequency ultrasound applications.
Lead-zirconium-titanate (PZT) particles synthetized by solid states synthesis
were dispersed in ethanol using ammonium polyacrylate (PAA). The
electrophoretic deposition of PZT particles was performed at a constant-current
mode. PZT thick-films deposited at 1 mA for 60 seconds were sintered at 900oC
for 2 hours in a PbO-controlled atmosphere. The scanning-electron microscopy
(SEM) analysis shows that the thickness of PZT layer is uniform and that the
pores are homogeneously distributed within the layer. The complex electrical
impedance was measured and fitted by KLM scheme in order to deduce the
dielectric, mechanical and piezoelectric parameters of the thick-films. The
density and thickness of PZT thick films are used as inputs and the thickness
coupling factor kt, dielectric constant at constant strain and resonant
frequency are deduced. The results show that homogeneous PZT thick-film
structures with tailored thickness and density prepared by EPD and sintering
having a resonant frequency around 20 MHz can be used for noninvasive medical
ultrasound imaging and diagnostics.
