| Recently, it was found that a very large longitudinal and transverse electrostrictive strain can be achieved in Poly (vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymers under a proper electron irradiation treatment. Further more, because of the relatively high elastic modulus, the copolymer also exhibits a high elastic energy density which is crucial for many electromechanical applications. Many useful results regarding changes in the crystalline phase and morphology of the P(VDF-TrFE) had been obtained. In this thesis, the microstructure, mode of chemical bonding, longitudinal strain, dielectric, piezoelectricity and ferroelectricity of electron irradiated P(VDF-TrFE) copolymer was studied. The relation between its physical performance and microscopic structure was analyzed. Further more, the phase transition behaviors of metastable phase induced by different applied fields were studied by X-ray to clarify the possible reasons for giant electrostriction, and the reasonable interpretation was presented.Flextensional transducers consisting of a piezoelectric disk sandwiched between two metal shells have attracted much interest in the last few years. The so-called moonie and cymbal transducers are essentially miniaturized version of flextensional. They can convert and amplify the small radial displacement into a much larger axial displacement normal to the surface of the caps. In this paper, the relative better geometry has been analyzed by ANSYS finite element software. It was found that the Cymbal transducer showed more axial displacement with less end cap thickness and Young's modulus, higher electric field on ceramic disk, bigger cavity diameter, and an appropriate cavity height.
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