Dielecteric Permittivity and Relaxation Phenomena in smectic Phases

Dielectric permittivities were measured on compounds having different smectic phases in broad temperature intervals. Both the parallel and the perpendicular component of permittivity are given and the variationsare interpreted. The intensity of the low frequency dielectric dispersion is interpreted by Bordewijk's formula and dipole-dipole correlation. The temperature dependences of the relaxation time in the different liquid crystalline phases are given. A small break was found at the N-SmA, SmA-SmC, SmB-SmF phase transitions, an order of magnitude change at the SmA-SmBand SmC-SmB phase transition, and a definite stepat the SmF-SmG phase transition. The big change at these last three phase transitions is interpreted by the appearance of the collective librational modes.