PIEZOELECTRIC POLYMER MATERIAL, PROCESS FOR PRODUCING THE SAME AND AN ULTRASONIC TRANSDUCER UTILIZING THE SAME

摘要

A piezoelectric polymeric material having utility in ultrasonic transducers is disclosed which consists essentially of a copolymer of about 65 to 82 mol percent of vinylidene fluoride and about 35 to 18 mol percent of ethylene trifluoride. The polymeric material is formed into a film of the desired thickness and then heated to a temperature greater than about the crystal phase transition temperature and less than about the melting-point temperature to produce a heat-treated film. The heat-treated film is poled in an electrical field of from about 50 to about 1,500 kilovolts per centimeter to give the film a thickness extensional electromechanical coupling factor of at least 0.05 and preferably greater than 0.2.