Electric field‐induced piezoelectricity in polymer film

Abstract

synopaisAn apparatus is devised for measuring the real and imaginary components of the piezoelectric strain constant d = d' -i d ' for polymer films with a d.c. bias field. Electric fieldinduced piezoelectricity is observed for films of several types of polymer. The ratio of the piezoelectric constant to the d.c. bias field gives (e + K)/G, where t is the dielectric constant, K is the electrostriction constant, and G is the elastic constant. The temperature dependence of the field-induced piezoelectricity gives, therefore, combined information of dielectric and elastic properties of polymers. After heating to about 95OC followed by cooling to room temperature, maintaining a constant d.c. bias on a poly(viny1 chloride) film, piezoelect.ricity is observed a t null d.c. field, which suggests the introduction of a residual polarization in the film.

Electric Field-Induced Changes in Odd-Numbered Nylons

“…Further, if the bulk polarization responsible for the piezoelectric activity resided in the amorphous regions, then it would be anticipated that heating the films to temperatures above the glass transition temperature (Tg) (-50°C for nylon 11) would lead to depolarization and a corresponding decrease in piezoelectric activity. This was reported, for example, in poled films of amorphous poly(vinyl chloride) 14 . This was not observed for odd-numbered nylons and, in fact, the piezoelectric coefficient, d 3 1 , was found to increase dramatically above Tg Finally, even though several X-ray diffraction studies of nylon 11 had been made by various investigators 5 , 13 , 17 -19 , no definitive X-ray crystal structure determination had been carried out for any of the various polymorphic forms reported.…”

Piezoelectric Effect in Composite Polyurethane–Ferroelectric Ceramics

“…The components of piezoelectricity in phase and 90 out of phase with the stress are cancelled by adjusting two potentiometers. According to Zimmerman [12] at the null condition, the potentiometers give the value q H and q HH related with d H and d HH by…”

Electrostriction of polarizable materials: Comparison of models with experimental data

“…[14][15][16][17][18][19][20][21] In this article, we present a method for describing electrostriction of arbitrary isotropic microstructures ͑amorphous or cubic crystalline͒. We relate the dielectric parameters a 1 and a 2 to the microstructure without employing the Lorentz cavity formalism.…”