Novel characterization method of ions in liquid crystal materials by complex dielectric constant measurements

The frequency dependence of the complex dielectric constant of liquid cryst al materials doped with tetra-n-butylammonium iodide (TBAI) is investigated in the low-frequency region, and the experimental results are analyzed in terms of space charge polarization. The contribution from an electric doubl e layer is also taken into consideration in the analysis. By means of curve fitting utilizing theoretical expressions of the space charge polarization , five sets of diffusion coefficient and density values are obtained for mo bile ions. It is confirmed by experiments on the temperature dependence tha t five kinds of ions follow Walden's rule, and verified from the viewpoint of ion radii that two of the five kinds of ions are TBA(+) and I-. The freq uency-dependent dielectric properties, which are characteristic of the beha viors of ions, can be well explained by this study and the analytical metho d introduced here is considered to be powerful for the evaluation of the at tributes of mobile ions.