| Popis: |
When the piezoelectric ceramic, PZT is used in the water it needs matching layers for efficient energy transmission. PZT is known as the proper piezoelectric material for the transmitter by reason of the large electromechanical coupling factor. So actually PZT has been used for the nondestructive testing or ultrasonic diagnostic instrument as good material. In the meantime, there is a kind of polymer by the name of PVDF. Its acoustic impedence is similar to water, so PVDF does not need matching layers but it is not a proper material for the transmitter because of the small electromechanical coupling factor. However, the receiving sensitivity of PVDF is very flat through the wide frequency range. So it is known as a proper material for the receiver like wideband hydrophone. Therefore in this paper it is suggested that the transducer which transmits and receives signals by PZT and PVDF, respectively, could be constructed compositively, and the transmitting and receiving feature of the transducer was investigated theoretically and experimentally. |
