Beschreibung:
For ferroelectric crystals with a second order transition the phenomenological theory predicts an infinite value of the dielectric constant at the CURIE-point. The highest value observed in the case of Rochelle salt is only about 104. This is not caused by the methods of sample preparation or measurement but by a dispersion of the permittivity. The temperature dependence of the dielectric constant and of the dielectric modulus (dielectric impermeability) at constant frequency is examined. The influence of several relaxation mechanisms on the formation of the spontaneous polarization is discussed.