INTERNAL LOSSES IN POLYVINYLIDENE FLUORIDE (PVF2) ULTRASONIC TRANSDUCERS

The dielectric and acoustic losses in oriented PVF2 have been measured from 0.1 MHz to 100 MHz and from 1.5 MHz to 39 MHz, respectively, in the direction perpendicular to the stretching direction at room temperature. A broad absorption peak located at around 5 MHz is observed in each case. The locations of these absorption peaks are of great disadvantage for ultrasonic transducer fabrication. The longitudinal acoustic velocity in the direction perpendicular to the stretching direction is also measured from 1.5 MHz to 39 MHz at room temperature. It is found that the velocity increases monotonically in this frequency range. As a result, the resonance frequency of a PVF 2 transducer will be affected proportionally.