Electromechanical nonlinearity of ferroelectric ceramics and related non-180 domain wall motions

Using an optical interferometer and other experimental techniques, the mechanical and dielectric response of lead zirconate titanate Pb(ZrxTi1 _x)03 ceramics to an a.c. electric field have been investigated directly. The experimental results demonstrate the importance of the domain wall motion in generating the electromechanical nonlinearities in ferroelectric ceramics. It has been verified that the couplings between the acoustic vibrations and the movement of domain walls is an important factor in terms of extrinsic properties of ferroelectric polycrystalline materials. A phenomenological theory has been extended to describe the extrinsic contributions to the piezoelectric, elastic and dielectric properties. These effects can be attributed to both the linear and nonlinear vibrations of non-1800 domain walls in ferroelectric ceramics. The proposed theory shows qualitative agreement with the experimental results.