Dielectric, electro optic and X-ray studies of a room temperature ferroelectric mixture

Abstract Dielectric spectra for the SmA* and SmC* phases of a room temperature ferroelectric liquid crystalline mixture FELIX-008 have been studied in the frequency range from a few Hz to 13 MHz. It has been found that in the vicinity of the SmA*-SmC* transition there is a pronounced soft mode dielectric spectrum, the dielectric parameters of which obey a Curie-Weiss law given by the mean-field theory. In the SmC* phase a distinguished Debye-type dielectric spectrum of the Goldstone mode has been detected, and upon increasing the bias field to 35 V it is suppressed and a new non-Debye-type dielectric spectrum-originating most probably from the so-called domain mode-shows up. Spontaneous polarization and tilt angle measurements show that the transition SmA*-SmC* is of the second order type. The dielectric and electro optic studies make it possible to compute the rotational viscosity, which is of great importance for practical applications. It turns out that the energy barrier for rotational viscosity (19.6...