Converse electrostriction in polymers and composites

The evaluation of electrostrictive properties of low permittivity dielectri cs requires extremely sensitive instrumentation. In the present work, a mod ified compressometer capable of resolving fractional changes in capacitance of the order of 10(-6) is used. In the compressometric method, a high sens itivity capacitance bridge, GenRad 1615, is coupled with two lock-in amplif iers to detect attofarad (19(-18)F) level capacitance changes caused by in- phase cyclic uniaxial stresses on the samples. In studying low-permittivity polymers, we have obtained extensive electrostriction data, which along wi th widely accepted data on ferroelectric materials and soft polymers, verif y the linear relationship between electrostriction coefficient (Q) and the ratio of elastic compliance and dielectric permittivity (s/epsilon(0)epsilo n(r)). This leads to an effective way to predict the electrostriction coeff icient in dielectric materials. (C) 1999 Elsevier Science S.A. All rights r eserved.