AC impedance studies of copper doped silica glass

Copper doped silica glass with nominal composition 10Cu (mol%)-90SiO(2) (mol%) is prepared using the sol-gel method. The dc conductivities are Arrhenius temperature dependent with activation energy 1.0 eV. The conducting species is attributed to the un-reduced Cu+ ions. The Kohlrausch-Williams-Watts function, phi(t) = exp[-(t/tau(0))(beta)], and the coupling model are utilized for analyzing electric modulus at various temperatures. The analyses indicate that the ionic relaxation is coupled with the structural relaxation, the decreasing of beta at 550 degreesC is due to the approaching the glass transition temperature of the sample. The dielectric constants at high frequency limit increase with temperature initially and then level off at temperatures above 550 degreesC; while, the dissipation factors increase exponentially with temperatures. The increase of dielectric constants and dissipation factors with temperature changes are explained by the net polarization in the medium at high frequency. (C) 2003 Elsevier Science B.V. All rights reserved.