Re-entrant ferroelectric phases in binary mixtures of ferroelectric and antiferroelectric homologues of a series with three chiral centers

• Published in: The Journal of chemical physics 2001-11, Vol.115 (19), p.9036-9041
• Main Authors: Novotná, Vladimı́ra, Glogarová, Milada, Hamplová, Věra, Kašpar, Miroslav
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.1412871

In binary mixtures composed of homologues from a series derived from 4-alkoxybiphenyl- 4′-carboxylic acid exhibiting ferroelectric (FE) and antiferroelectric (AF) phases, a re-entrant FE phase may be induced in a certain concentration region, which is miscible with the SmC* phase. Dielectric spectroscopy study revealed a softening of the antiphase mode in the AF phase, which is responsible for the appearance of the re-entrant phase. The helix twist inversion occurs at the low temperature limit of the (AF) phase so that the helix handedness of the upper and lower temperature FE phases have opposite sense. The values of spontaneous polarization and the spontaneous tilt angle evolve continuously with the concentration, while dielectric strength exhibits a maximum for a certain concentration of homologues. All phase transitions existing in the binary mixtures are sharp and divide homogeneous phases in contrast to results reported in E. Gorecka et al. [Phys. Rev. Lett. 81 2946 (1998)], where a frustrated cluster phase exists. The reason is in different behavior of interlayer interactions at the FE-AF phase transition.