PERFORMANCE OF MULTILAYERED ULTRASONIC TRANSDUCERS COMPRISING VINYLIDENE FLUORIDE AND TRIFLUOROETHYLENE COPOLYMER FILMS AND FERROELECTRIC CERAMIC PLATES

Frequency and impulse response characteristics of multilayered ultraso nic transducers comprising forward films of vinylidene fluoride and tr ifluoroethylene copolymer (P(VDF-TrFE)) and backward ferroelectric cer amic plates of lead-zirconate-titanate (PZT) and a backing load, are s tudied both theoretically and experimentally. These transducers can be driven in three operation modes: (1) P(VDF-TrFE) as a transmitter and a receiver. (2) PZT as a transmitter and a receiver, and (3) PZT as a transmitter and P(VDF-TrFE) as a receiver. It is found that, owing to the great difference in their acoustic and,dielectric properties, PZT plates and P(VDF-TrFE) films operate independently at different frequ encies, and that, in operation mode (3), the multilayered transducers exhibit broad frequency bandwidth or shorter impulse response characte ristics with high sensitivity and high S/N ratio.