Dielectric spectroscopy up to 20 GHz of LiCl/H2O solutions

Abstract

Detailed measurements of the complex dielectric function ε=ε′−iε″ as functions of frequency between 45 MHz and 20 GHz and concentration c are presented and analyzed for LiCl/H2O solutions. In this frequency range, the dielectric response is due to free water molecules and the response of the bound water occurs at lower frequencies and is not observed. From the data, several parameters—the static and high frequency limiting values ε0 and ε∞, the dc conductivity σdc, the dielectric relaxation time τd, and the hydration number nhyd—are extracted. The dissociation is observed to be incomplete suggesting the presence of undissociated ion pairs. A dissociation parameter is inferred from the σdc data. A model which views the liquid as composed of free water, hydrated single ions, and hydrated ion pairs is used to analyze the ε0 data. With inclusion of the dissociation parameter, the model describes the data reasonably well for c≤5.1 M. At higher concentrations, a unique relaxation time is not observed indicating glasslike behavior.