Theoretical approach to effective electrostriction in inhomogeneous materials

An analytical approach is developed for the effective electrostriction, a nonlinearly coupled electromechanical effect, in inhomogeneous materials based on Green's-function method. For an isotropic composite containing randomly oriented ferroelectric crystallites with cubic symmetry, we derive the first effective-medium-like formulas for calculating its effective electrostrictive coefficients. The effects of microstructural features (such as volume fraction, crystallite shape and orientation, and connectivity of phases) on the effective electrostrictive coefficients are illustrated numerically and discussed. The calculations show that it is possible to develop new electrostrictors combining large electrostriction with mechanical flexibility by choosing the best combination of ferroelectric ceramics and polymer.