Generation of very high‐frequency ultrasonic waves using thin films of vinylidene fluoride‐trifluoroethylene copolymer

Electromechanical properties of thin films of vinylidene fluoride‐trifluoroethylene copolymer [P(VDF‐TrFE)] and their application to ultrasonic transducers were studied in the frequency range of 50–250 MHz at room temperature. A 5‐μm‐thick P(VDE‐TrFE) film resonating at 250 MHz in thickness extensional mode exhibited a large electromechanical coupling factor of 0.26. The dielectric and elastic constants were also studied in this frequency region. A transducer using a 3‐μm‐thick film exhibited a large conversion efficiency (6.5 dB at 150 MHz), and good impulse response (30 ns ring‐down time width) in water. A concave transducer transmitted a well‐focused ultrasonic beam (35‐μm beamwidth).

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