Volume 110, Issue 6, December 2001
Index of content:
- TRANSDUCTION 
110(2001); http://dx.doi.org/10.1121/1.1416905View Description Hide Description
A new technique to experimentally determine the electrostrictive coefficients of thin polymer films is presented. This technique is a second-order extension of the first-order quasistatic method for the measurement of piezoelectric coefficients previously introduced by Guillot and Jarzynski [J. Acoust. Soc. Am. 108, 600–607 (2000)]. In the present method, electrically induced strains are measured optically on a rubber-encapsulated sample. These strains are used in a Rayleigh–Ritz procedure that minimizes the total energy of the sample and whose output is a set of three tensile electrostrictive coefficients. The total energy of the sample includes elastic contributions from the polymer and the encapsulating rubber as well as two quadratic electromechanical terms corresponding to Maxwell stress and to electrostriction. Therefore, the external electrostatic effects can be separated from the intrinsic electrostrictive behavior, and the measured coefficients are true material properties. Data obtained on two types of polyurethanes submitted to a bias field of approximately 4 MV/m at 2 kHz and at room temperature are presented. It was found that these materials possess very large electrostrictive coefficients and that the Maxwell stress effect is responsible for less than 13% of their total electromechanical behavior.