STRUCTURAL ORDERING IN FERROELECTRICS - ITS EFFECT ON THE ACOUSTIC PROPERTIES OF POLYCRYSTALS WITH A COMPLEX PEROVSKITE STRUCTURE

The paper sums up a study of acoustoelectric effects that occur in fer roelectrics as they undergo a structural ordering under the action of an electric held. Emphasis is placed on complex ferroelectrics with a perovskite structure. Analytical expressions are derived to describe t he relationship between the velocity of acoustic waves and the magnitu de and orientation of the controlling electric field. The velocity and polarization of acoustic waves are found to vary with the controlling field, in a manner that is strongly affected by the anisotropy of the elastic constants of single-crystal grains.