Dielectric spectroscopy of some heteronuclear amino alcohol complexes.

The temperature dependent dielectric spectroscopic properties of two heteronuclear complexes of monoethanolamine (MEA) at a wide temperature range (303-413 K) were investigated by impedance spectroscopy, in the frequency range from 100 Hz to 100 kHz. The frequency dependence of the impedance spectra plotted in the complex plane shows semi-circles. The Cole-Cole diagrams have been used to determine the molecular relaxation time, tau. The temperature dependence of tau is expressed by thermally activated process. Relaxation frequencies corresponding to the rotation of the molecules about their long axes are expected to lie above 10 MHz and exhibit Arrhenius behavior, where a single slope is observed with activation energy values equal to 0.67 and 0.78 eV. The ac conductivity sigma(ac) (omega) is found to vary as omega(s) with the index s<or=1, indicating a dominant hopping process at low temperatures. The dielectric permittivity dependence as a function of frequency and temperature have been determined and showed a strong dispersion at frequency lower than 10 kHz. Capacitance and losses, tandelta, decreased with increasing frequency and increased with increasing temperature. The analysis of the data reveals that such characteristics are in good agreement with semi-conducting features based mainly on the hopping mechanism.