DIELECTRIC-DISPERSION OF FERROELECTRIC CERAMICS AND SINGLE-CRYSTALS BY SOUND GENERATION IN PIEZOELECTRIC DOMAINS

Periodic domain configurations with alternating 180 degrees and 90 deg rees domains are not completely mechanically clamped up to microwave f requencies, Above the acoustic resonance of the ferroelectric sample, therefore, the dielectric constant comprises contributions which can b e attributed to the free dielectric constant, Up to microwave frequenc ies the domains are piezoelectrically active; they emit longitudinal a cid shear thickness waves into the surroundings which cause dielectric loss in the sample, The dielectric step from the free condition to th e damped condition at the relaxation frequency is on the order of Delt a epsilon approximate to 10-100. This step is much smaller than the st ep caused by the emission of shear waves from 90 degrees domain walls.