AC conductivity and dielectric measurements of bulk magnesium phthalocyanine (MgPc)

The AC conductivity, sigma(ac)(omega) for bulk magnesium phthalocyanine (MgPc) in the form of compressed pellet in the frequency range of 1-500 kHz and in a temperature range of 303-443 K with evaporated ohmic Au electrodes have been investigated. The frequency dependence of the impedance spectra plotted in the complex plane shows semicircles. The Cole-Cole diagrams have been used to determine the DC conductivity. The AC conductivity, sigma(ac)(omega), is found to vary as omega(5) in the frequency range of 1-500 kHz. At high range of frequency, s < 1 and it decreases with increasing the temperature. The variation of s with temperature suggests that the AC conduction is due to the correlated barrier hopping (CBH). The dielectric constant, epsilon', and dielectric loss, epsilon '', for bulk MgPc were decreased with increasing frequency and increased with increasing temperature. (C) 2009 Elsevier B.V. All rights reserved.