ELECTROSTRICTION - NONLINEAR ELECTROMECHANICAL COUPLING IN SOLID DIELECTRICS

Electrostriction is the basis of electromechanical coupling in all ins ulators. The quadratic electrostrictive strain x(ij) associated with i nduced polarization components P-k and P-l is given by x(ij) = Q(ijkl) P(k)P(l). Two converse electrostrictive effects may also be defined. I n this paper, some trends in structure-property relationships that gov ern electrostriction are identified,, along with the problems that lim it our understanding of this fundamental electromechanical property. E lectrostrictive coefficients range from the similar to 10(-3) m(4)/C-2 in relaxer ferroelectrics to similar to 10(3) m(4)/C-2 in some polyme rs. High-sensitivity techniques, such as interferometry or compressome try, are necessary to accurately measure electrostrictive effects in m ost insulators. But even in low-K dielectrics, electrostrictive stress es may initiate breakdown in high-field environments such as microelec tronic components with small dimensions, high-voltage insulators, or i n high-power lasers. In polymeric materials, charge injection mechanis ms may produce local electric field concentrations that can cause larg e electrostrictive strains. The electromechanical properties in polyme rs have also been observed to vary with the thickness of the specimen. A brief description of the anharmonic nature of electrostriction and its frequency dependence is included.