Miyo Suzuki

Piezoelectric and ferroelectric properties of P (VDF-TrFE) copolymers and their application to ultrasonic transducers

Abstract The copolymers of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) have been found to be effective ultrasonic transducer materials because of their large electromechanical coupling factor kt . On the basis of the results obtained by SEM, X-ray diffraction, and ferroelectric polarization reversal studies of copolymer films, the large kt is ascribed to their high remanent polarization, which may originate from high crystallinity and preferential orientation of well-grown crystallites. Various single element transducers for medical ultrasound imaging have been developed utilizing PVDF and P(VDF-TrFE) films. The performance of these transducers is in good agreement with a theoretical prediction in which their dielectric and mechanical losses are taken into account. The P(VDF-TrFE) transducers have a two-pathway sensitivity 10 dB higher than that of PVDF transducers. They give high resolution medical images much superior in quality to those obtained with conventional ceramic transducers. Linear ...

Analysis of Frequency Response Characteristics of Polymer Ultrasonic Transducers

Piezoelectric polymers have large dielectric and mechanical internal losses. In this study, we introduced internal losses into Masons equivalent circuit, and analyzed the effects of these losses on the transducer response, mainly in the frequency domain. To prove the validity of the theoretical analysis, we fabricated polymer transducers of several backing load types which are effective for practical use, using vinylidene fluoride and trifluoroethylene copolymer films, and evaluated their frequency and impulse responses. The experimental results are in good agreement with the theoretical prediction. We conclude that a consideration of the internal losses is essential for the proper design and correct evaluation of polymer transducers.