Ferroelastic domain walls as powerful shear wave emitters at microwaves

Abstract

Abstract The strong dielectric dispersion in ferroelectric ceramics near 1 GHz is caused by the emission of sound waves from domain walls and from piezoelectric domains. The ferroelastic domain walls are very effective shear wave emitters. A displacement of these walls by electric or elastic fields causes a shift of the matter above and below the wall in opposite directions parallel to the wall. At high frequencies this alternating mass shift is the source of sound waves. The shear waves are emitted into the adjacent domains and crystallites where they are scattered and attenuated. The relaxation frequency is determined by the width of the domains and by other factors which govern the domain wall mobility. Above the relaxation the masses can no longer follow the excitation. The domain walls then are clamped by this inertia. In this case the contributions of the domain walls to the dielectric, piezoelectric and elastic constants are frozen in. The relaxation step can be up to δe≈ 1000. The transducer prope...