Dielectric spectroscopy of a ferroelectric nematic liquid crystal and the effect of the sample thickness

Ferroelectric nematogens containing a methylthio group

“…2,8,10,12,14–16,18,58–60 However, it has been recently reported that there may be a relationship between these values and the cell thickness. 61 The polar character of the N F phase was further confirmed by the polarisation switching behaviour. When an AC voltage was applied a single current peak per half cycle was registered and this corresponded to a large spontaneous polarisation of 3.1 μC cm −2 , Fig.…”

The Emergence of a Polar Nematic Phase: A Chemist's Insight into the Ferroelectric Nematic Phase

“…This has been highlighted recently by reports of DIObased molecules also exhibiting a ferroelectric smectic A phase, Figure 1. [31,38,45] For many of the materials reviewed here, the polar character of the N F phase was described by the appearance of a strong dielectric relaxation mode, [14,[19][20][21]24,25,33] the exact magnitude of which, as was mentioned previously, has come under some discussion recently, [27] but this review will not look to resolve this and will use the phase sequences as they have been reported in the literature. The other method used in the determination of the N F phase was polarised optical microscopy and the observation of characteristic banded textures, with examples of these shown in Figure 3.…”

“…Indeed, these include some which mean that the phase may have real application potential. Some of these properties include: being easy to align; [9,10] having a strong non-linear optical response; [11][12][13][14][15] high polarisation values; [7,8,16,17] large dielectric permittivity [18][19][20][21][22][23][24][25][26] (although there has been some debate around the exact magnitude of these permittivity values) [26,27] and switching occurs for very low electric fields. [7,8,20,[28][29][30][31][32][33] While there has been a large upsurge in materials in the last couple of years that have been reported to exhibit the ferroelectric nematic phase, the majority of these compounds fall into a relatively small structure space.…”

Room-temperature ferroelectric nematic liquid crystal showing a large and diverging density

“…Dielectric measurements have reported large dielectric permittivity values on the order of 10 4 for RM734 16 and for DIO, 3,17 although the validity of these has been questioned. 18,19 Polarisation investigations have found values of spontaneous polarisation for RM734 (6 mC cm À2 ) 5,20 and DIO (2.5-6 mC cm À2 ) 3,17 which are comparable with polar columnar (5.8 mC cm À2 ) 21 and bent core liquid crystals (LCs) (0.5-0.8 mC cm À2 ). 22 The measured N F spontaneous polarisation values is far larger than typical chiral smectic C materials (e.g.…”