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

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