3K-1 Integrated and Flexible Piezoelectric Ultrasonic Transducers

Thick (>40 mum) ceramic films as piezoelectric and ultrasonic transducers (UTs) have been successfully deposited on metallic and non-metallic substrates by a spray technique. In the film fabrication a composite consisting of piezoelectric powders well mixed with solution of high dielectric constant is directly sprayed onto the substrate. It is then dried, fired or annealed by heat. Multiple coating is used to achieve preferred thicknesses. A corona poling is utilized to achieve the piezoelectricity of the film. The top electrode is accomplished by a painting method. All fabrication processes can be carried out on-site and by handheld devices. Integrated ultrasonic longitudinal, shear, surface and plate wave transducers have been made. The same technology has been also used to fabricate flexible transducers consisting of a thin substrate, a piezoelectric ceramic film and electrodes. The flexibility is realized owing to the porosity of piezoelectric film and the thinness of the piezoelectric film, substrate and electrodes. All transducers have been tested at least up to 150degC. Their applications for non-destructive testing of different materials are demonstrated