Phase ferrielectric

Initially the octyl to dodecyl compounds were prepared and these were found to exhibit relatively normal behavior, i.e. smectic A phases were found for the lower homologues with smectic and ferroelectric smectic C phases occurring for the higher members. However, when the tetradecyl homologue was examined in the polarizing transmitted light microscope, an iridescent helical mesophase was observed which upon cooling underwent a further phase transition to a ferroelectric smectic phase. In addition, this compound was also found to exhibit antiferroelectric and ferrielectric phases. 

Then, for paraelectric SmA phase both = 0 and = 0, for ferroelectric SmC phase 0 but = 0 as discussed in Section 13.1, for antiferroelectric SmC A phase = 0 but f 0, and for ferrielectric phases SmC F/ both 0 and AP 7 0. Now the Landau expansion of the free energy in the vicinity of transitions between the paraelectric, ferroelectric and antiferroelectric phases will operate with two order parameters and both coefficients at the terms in the free energy are considered to be dependent on temperatiue ... 

The two polarizations Pp and Pap may be taken as secondary order parameters coupled with the genuine order parameters. As a result, depending of the model, the theory predicts transitions from the smectic A phase into either the synclinic ferroelectric phase at temperature Tp or into an anticlinic antiferroelectric phase at Tap- One intermediate ferrielectric phase is also predicted that has a tilt plane in the i + 1 layer turned through some angle

tilt plane in the i layer. The models based on the two order parameters are of continuous nature (9 may take any values) and, although conceptually are very important, caimot explain a variety of intermediate phases and their basic properties. 

SmC f/i biaxial ferrielectric phase with 31 periodicity and finite P. It manifests ORP, which may change sign at a certain temperature. 

Smectic Liquid Crystals Antiferroelectric and Ferrielectric Phases... 

Questions still exist the SmX phase exhibiting V-shaped switching is a new phase or there are some conventional phases such as ferroelectric, antiferroelectric, and ferrielectric phases. One of the most important experiments remaining is the quantitative measurement of the tilting correlation between adjacent layers. This is a future problem. 

The application of an electric field has a considerable effect on the phase transition points in MHPOBC [210] the phase diagram (electric field versus temperature) is shown in Fig. 26. A very narrow low-temperature ferrielectric phase is seen (FIL) between the SmC and SmC phases mentioned earlier. In addition, even a weak field strongly influences the boundary between the SmC and SmC phases. Further inves-... 

Fabry-Perot based wavelength filters 809 Fabry-Perot etalon, Brillouin scattering 719 Fabry-Perot resonator 579 fan textures 436 fanned-out inputs, SLM 798 Faraday balance 213 faults, thermography 832 ferrielectric phases (FIP) 120 external fields 513... 

FIGURE 2.17 Polarized microscopic image of the homeotropic texture of the three-layer intermediate (also known as the ferrielectric phase). The three-layer phase is optically indistinguishable from the four-layer phase, but the two phases can be clearly differentiated using the resonant x-ray scattering technique. ... 

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