AC impedance studies of copper doped silica glass

Copper doped silica glass with nominal composition 10Cu (mol%)–90SiO2 (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, φ(t)=exp[−(t/τ0)β], 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 β at 550 °C 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 °C; 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.