Wide-band Multi-layer Ultrasonic Transducers Made of Piezoelectric Films of Vinylidene Fluoride-Trifluoroethylene Copolymer

Piezoelectric films of vinylidene fluoride-trifluoroethylene copolymer are applied to construct a wide-band ultrasonic transducer with multi-layered structure. One of the component films has a polarization direction opposite to the others. Amplitudes of even- and odd- resonances are adjusted by combination of copolymer films with different thicknesses. A wide-band transducer whose bandwidth in more than twice that of a single-layer transducer is obtained. The design principle and the method for preparing this wide-band transducer are presented.