Effects of electric double layer and space charge polarization by plural kinds of ions on complex dielectric constant of liquid crystal materials

The complex dielectric constant of a liquid crystal material, 4-cyano-4'-al kyl-biphenyl (5CB), was measured in low-frequency regions below 1000 Hz. Th e anomalous increasing behavior was analyzed using an equivalent circuit wh ich takes two kinds of contributions into account: one is from the electric double layer and the other is from the space charge polarization. It was f ound by numerical calculations that these two effects exhibit different dep endences of dielectric dispersion on the thickness of a specimen, and both effects were successfully distinguished in the experimental results. In the analysis of the space charge polarization, the experimental results were b est fitted by the calculated results with five kinds of ions in terms of th e diffusion coefficient. These measurements can be applied to a precise det ermination of the attributes of plural kinds of ions, such as the diffusion coefficient and the number density.