Dielectric properties of some minerals of western Rajasthan

Abstract

Dielectric constant ε' and loss ε" of dry samples of clay, siliceous earth, fuller’s earth, gypsum, lignite, calcite, tourmaline and magnesium rock of opencast mines of western Rajasthan, India, were studied in the frequency range 100 Hz - 100 kHz and also at X-band microwave frequencies. It is observed that the values of ε' decreases with increase in frequency in low frequency region. Exceedingly high ε' values were found for clay, siliceous earth and, fuller’s earth at lower frequencies in the 100 Hz to 100 kHz frequency range. The complex plane plots (ε" versus ε') of these minerals are the Cole-Cole arcs. The low frequency limiting dielectric constant ε₀, high frequency limiting dielectric constant ε∞, relaxation time of dipole rotation  and, distribution parameter α of these materials were determined using the Cole-Cole plots. All these minerals have large value of α, and their  values varies in the range from ≈ 0.1 to 11 ms. Frequency dependent ac conductivity of these minerals has been determined and discussed and, the contribution of sample bulk density and percent weight of the constituents of their chemical composition on the microwave values of ε' and ε" has been explored for the studied samples.