Electrode effects in dielectric spectroscopy of colloidal suspensions

Theory of small-signal ac response of a dielectric liquid containing two groups of ions

“…More recently, simple versions of the equations of Macdonald, relevant to the case in which the impurities dissolved in the liquid are completely dissociated, have been discussed for several cases. [6][7][8][9][10][11][12][13][14] Our goal now is to generalize the analysis of Macdonald to the case in which the dielectric liquid contains two groups of ions. Very detailed treatments of two carrier systems exist in the liquid and solid electrochemistry.…”

Analysis of the Dielectric Permittivity of Suspensions by Means of the Logarithmic Derivative of Its Real Part

“…In order to analyze the EP contribution, we will follow the approach by Cirkel et al (16). Let us assume for the moment that the measuring cell consists of two planar electrodes separated by a distance L; the cell contains a simple ionic solution or even a colloidal dispersion, but it will be admitted that in the frequency range of interest no relaxation occurs, that is, the dielectric permittivity of the system is frequency-independent, and equal to some value ε 0 ε m .…”

“…There is, however, a serious difficulty that has likely prevented the method from being more extensively used: this is the phenomenon of electrode polarization (EP). Recall that it is related to the existence of the metal/electrolyte solution interface, which manifests itself as a potential barrier at the latter and can be modelled as a complex impedance Z * EP in series with the true sample impedance, Z * s (14)(15)(16). The important point here is that the presence of Z * EP can lead to apparent low-frequency dielectric constants much higher (even orders of magnitude higher) than the actual value of the suspension.…”

Wide-frequency-range dielectric response of polystyrene latex dispersions

“…Although the nature of this problem is poorly understood, various heuristic correction methods have been proposed [11][12][13][14][15][16][17], and there have also been some theoretical proposals to deal with the problem [18][19][20]. Particularly interesting and encouraging are the results reported first by Cirkel et al [21] and then by Hollingsworth and Saville [22] who give two different analytical descriptions of the complex dielectric permittivity of an ideally polarized flat electrode in a symmetric electrolyte, based on standard electrokinetic theory. In most experimental studies using dielectric spectroscopy, however, the frequency range inspected begins at around 5 Hz, thus missing part of the contribution of the EP which extends down to very low frequencies (mHz range).…”

“…In most experimental studies using dielectric spectroscopy, however, the frequency range inspected begins at around 5 Hz, thus missing part of the contribution of the EP which extends down to very low frequencies (mHz range). Hence, as one only observes the highfrequency tail of this contribution, it becomes difficult to apply the analytical expressions proposed in these theoretical models, and one has to have recourse to the simplification of their high-frequency asymptotic dependence [21,22], with which it is difficult to determine some parameters of the models. Also, one has to fit the entire frequency range of the dispersion of the dielectric constant and conductivity, so that one needs to have theoretical models available that correctly represent the behavior of the latex.…”