Low-frequency dielectric dispersion and microwave dielectric properties of dry and water-saturated limestones of Jodhpur region

Abstract

We investigated the complex dielectric constant of 17 different grades of dry and water-saturated limestone samples from the Jodhpur region in the frequency range of [Formula: see text] to [Formula: see text] and also at [Formula: see text] at room temperature. The Cole-Cole dielectric dispersion model was used to compute the values of low-frequency-limit dielectric constant, high-frequency-limit dielectric constant, dielectric strength, and principal value of the relaxation time for each dry limestone sample. The chemical composition, sample bulk density, and porosity of each sample studied were determined to learn which of these factors govern their dielectric parameters. Analysis of the low-frequency dielectric constant confirms that chemical composition and bulk density are the ma-jor factors governing the dielectric constant values; but for water-saturated samples, the frequency-dependent dielectric constant values are also sensitive to porosity and grain size. The ac conductivity of all of the dry samples increases with the increase in frequency from [Formula: see text] to [Formula: see text], but water-saturated samples have comparatively high conductivity; some samples have values independent of the frequency. The microwave dielectric constant of dry samples depends mainly on the amount of the constituents of the oxide, their chemical composition, and sample bulk density. The contribution of the measured dielectric-constant values of each oxide present in the sample is identified by using their density-reduced values of the dielectric constant. The porosity-dependent mixing equations for solid and fluid components of the system were also found suitable for determining the dielectric constant of water-saturated limestone samples at microwave frequency.