Dielectric spectroscopy of water at low frequencies: The existence of an isopermitive point

TL;DR

This study investigates the dielectric properties of water at low frequencies, identifying an isopermitive point where the dielectric constant remains unaffected by temperature changes, revealing a balance between ionic and dipolar effects.

Contribution

It introduces the concept of an isopermitive point in water's dielectric response and models water as a system of ions and dipoles to explain this phenomenon.

Findings

Identification of an isopermitive point at a specific frequency.

Demonstration of temperature dependence of dielectric constant below and above this point.

Explanation of the behavior through ionic and dipolar mechanisms balance.

Abstract

We have studied the real part of the dielectric constant of water from 100 Hz to 1 MHz. We have found that there is a frequency where the dielectric constant is independent of temperature, and called this the isopermitive point. Below this point the dielectric constant increases with temperature, above, it decreases. To understand this behavior, we consider water as a system of two species: ions and dipoles. The first give rise to the so called Maxwell-Wagner-Sillars effect, the second obey the Maxwell-Boltzmann statistics. At the isopermitive point the effect of both mechanisms in the dielectric response compensate each other.