Piezoelectricity in vinylidene cyanide/vinyl acetate copolymer and its application to ultrasonic transducers

The piezoelectric properties are measured for the alternative copolymer of vinylidene cyanide and vinyl acetate. It was found that a stretched polarized copolymer exhibited much larger values of electromechanical coupling constants, Kt, than did poly(vinylidene fluoride) films treated by the same poling conditions. Additionally, no piezoelectric decay occurs in the polarized copolymer after long-term heat treatments at or below 150°C. The copoymer has an acoustic impedance very close to that of water and hence, can efficiently couple acoustic energy into this medium. Properties of ultrasonic transducers using this copolymer are compared with those of poly(vinylidene fluoride).