Air-coupled UT transducers

Based upon piezoelectric composite materials, air borne ultrasonic probes with frequencies above 100 kHz were developed. These probes are characterized by a bandwidth larger than 50 % as well as a signal-to noise ratio higher than 100 dB. The essential part of the probes is a piezo-composite (1-3-configuration) developed at the IZFP. The piezo-composites are characterized by a high electroacoustic coupling coefficient (about 0.7), better aoustic matching to gas (acoustic impedance 6 to 10 MRayl in comparison to 35 MRayl of the piezo-ceramic) and a low mechanical quality factor. To further improve the efficiency of air coupled probes compressed air shoes and travelling wave transducers are in current development.