FERROELECTRIC POLYMER SINGLE CRYSTAL, METHOD OF ITS MANUFACTURE, AND PIEZOELECTRIC ELEMENT, PYROELECTRIC ELEMENT AND NONLINEAR OPTICAL ELEMENT USING THE METHOD

摘要

PURPOSE:To allow lamella crystal to grow in a certain direction in a membrane plane by preparing ferroelectric polymer consisting of a copolymer of ethylene trifluoride or tetrafluoride and vinylidene fluoride in the form of a film or fiber. CONSTITUTION:Polyvinylidene fluoride and ethylene tri- or tetra-fluoride are mixed to prepare a membrane using dimethyl formamide as a solvent, and the obtained membrane is uniaxially elongated approximately five times as large at room temp. The Curie point of the membrane is 123 deg.C while the melting point is 150 deg.C. The two membrane ends perpendicular to the elongating direction are fixed and the temp. is raised from room temp. at a rate of approx 5 deg.C/min, crystallized in the air at a temp. of 140 deg.C, followed by slowly cooling to the room temp. The resultant ferroelectric polymer consisting of coplymer of these crystals and vinylidene fluoride is shaped in a film or fiber. The singlecrystal film has good orientation of molecular chain and a good degree of crystallization, and its poling film exibits a large polarization so that the piezoelectric coefficient and the electro-mechanical coupling factor are increased.