CELLULAR POLYPROPYLENE FERROELECTRET FILM:PIEZOELECTRIC MATERIAL FOR NON-CONTACT ULTRASONIC TRANSDUCERS

摘要

Electromechanical properties of the cellular polypropylene ferroelectret films (EMFIT) evidence their high potential for the air-coupled ultrasonic applications. The disadvantage with respect to their low coupling factor could be compensated by the extremely low acoustic impedance. A figure of merit is proposed to compare and estimate piezoelectric materials intended for the air-coupled ultrasonic applications. Electron beam evaporation technology was adapted to the EMFIT films and films with two-sided Au and Al electrodes were prepared without reducing or suppressing of the electromechanical properties. Finally, air-coupling ultrasound transducers based on the EMFIT films were developed and characterized.