Dielectric and thermodynamic studies of Smectic-A–Smectic-C* phase transition in antiferroelectric liquid crystal: thermal hysteresis

We present the experimental evidence and theoretical studies of the para-ferroelectric phase transition in the chiral liquid crystal C12HH. The investigated compound presents a large SmC* range. Both microscopic observation and dielectric measurements show thermal hysteresis and coexistence phases at paraelectric (SmA)-ferroelectric (SmC*) phase transition. The thermal hysteresis is analysed in samples with different planar cell thickness. The SmA-SmC* phase transition under electric field is also investigated. Finally, the Landau free energy density is used to analyse the experimental measurements, showing a satisfactory agreement with experimental data.