Electron-irradiated electrostrictive P(VDF-TrFE) copolymer transducers

摘要

Ultrasonic transducers were fabricated using electron-irradiated electrostrictive poly(vinylidene fluoride-trifluoroethylene) [P(VDF 0.8-TrFE0.2)] copolymers. The transducers were tested in through-transmission mode by a piezoelectric P(VDF0.7-TrFE 0.3) receiver in the MHz range. Different dc voltage biased transmitting response was recorded when the transmitter was driven by a standard ultrasonic voltage source through a decoupling circuit. The amplitudes of voltage waveforms increased with the dc bias voltage from 0 to ±1000V and symmetric waveforms were observed for positive and negative field. The frequency spectrum were obtained by fast Fourier transformation (FFT) method with similar center frequencies and -6dB bandwidths compared with a normal copolymer transmitter. The electron irradiation seems to be responsible for the difference of peak frequencies and waveforms in the measurement results. The inversed voltage waveforms were also given by a graphic explanation. It is believed that the "induced" piezoelectric coefficient increased with the dc biased field, which may be the reason for the ultrasound generation of the transmitter.