5H-6 Fabrication and Characterization of Thick Film Piezoelectric Ultrasonic Transducers

Lead-zirconate-titanate fine powders mixed with chemical solutions have been used to fabricate 50 mum thick films. The fabrication methods include sol-gel spray, tape casting and screen printing. The substrates were 75 mum thick stainless steel membrane. The sol-gel spray technique included multiple coatings and each coating involved spray and heat treatment. Each layer was between 5 and 15 mum thick. For tape casting and screen printing, only one layer of 50 mum was directly cast and printed onto the substrate. Then films were treated in the furnace up to 650 degC for 5 to 30 minutes in this study. These films became piezoelectric through a corona poling technique. The relative dielectric constant of the sol-gel sprayed films was around 130 and those of the tape casting and screen printing ones were lower than 100. The capability of these films as piezoelectric flexible ultrasonic transducers was confirmed in the pulse-echo mode at several MHz for non-destructive testing at room temperature and 150 degC