Non-linear dielectric effect in an ethanol+dodecane critical mixture with minor amounts of ions

Abstract

A critical binary mixture with a low concentration of ions (tetramethylamonium chloride) was investigated by the non-linear dielectric method. It was observed that the addition of ions increases the critical anomaly of the non-linear dielectric effect. The increase was only observable at low frequencies of the measuring field. Possible explanations are presented and discussed. In spite of the very low concentration of ions, some evidence of crossover from Ising-like to the mean field behaviour was found.

Shift of the Critical Mixing Temperature in Strong Electric Fields. Theory and Experiment

“…According to theoretical expectation, the critical exponent z has a value of 0.59. Some experiments confirmed this value, ,, but in many cases a somewhat smaller exponent was obtained. ,, Rzoska and co-workers ,, pointed out that the critical exponent z = 0.59 is validated in an asymptotic region (far from T c and not very strong electric fields), whereas in the mean-field region (close to T c and strong E field) the exponent 0.37 seems to be supported.…”

“…Contrary to Debye–Langevin theory, in many cases the NDE increment is positive. A positive NDE increment is observed, for example, in the vicinity of a critical mixing point both in binary ,,− and in ternary mixtures . When the temperature and concentration are approaching the critical value, the NDE increment exhibits a divergence according to the equation normalΔ ε italicE 2 = italicD bg + italicD normalz italict − normalz where D bg is the backgroud conribution, D z is the positive critical amplitude, and z = γ + 2β ≈ 0.59. , The negative sign of the exponent in eq proves the large sensitivity of NDE method to critical phenomena.…”

Non-linear dielectric effect and critical phenomena in a ternary mixture cyclohexane+acetonitrile+p-xylene

“…This 'abnormal' NDE increment is a consequence of an influence of a strong external field on molecular association [5][6][7], tautomeric equilibriums [8,9] as well as thermodynamic and critical fluctuations [4,10]. In the vicinity of the critical mixing point very strong increase in the NDE increment is observed [11][12][13][14]. The anomaly of NDE in the vicinity of the critical consolute point can be explained on the basis of a droplet model proposed originally by Oxtoby and Metiu [19,20] and applied to dielectric properties by Goulon et al [21].…”