Electrophoretic deposition (EPD) process for lead zirconate titanate (PZT) thick films fabrication and high frequency medical imaging
Résumé
High frequency ultrasonic devices operating over 20 MHz are required for medical diagnostics including skin and eye imaging. The main component in an ultrasonic transducer is a piezoelectric material such as PZT. It is usually surrounded by one or several matching layers, a focusing lens and a backing. Geometric and electromechanical properties of the piezoelectric layer strongly contribute to transducer performance. High-frequency operation requires piezoelectric materials with a thickness of few tens of micrometers that can be obtained by thick-film technologies. The use of a lens in high-frequency transducers implies a significant decrease of transducer sensitivity due to losses. So our interest is to use geometrical focusing of the acoustical beam. For this, the piezoelectric layer must be curved. Here, electrophoretic deposition (EPD) is used to deposit patterned piezoelectric structures on curved substrates. A stable suspension and an optimized deposition process have been developed to deliver homogeneous, crack-free deposits with uniform thickness. Deposited films were sintered, functionally and electromechanically characterized. Thickness coupling factors similar to those measured in bulk ceramics were observed. Finally, the piezoelectric structures were used to fabricate high-frequency ultrasonic transducers which were characterized and integrated in an echographic probe to obtain in-vivo skin images.
Domaines
Acoustique [physics.class-ph]
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