Dark Current and Dielectric Relaxation of CdO⋅SiO₂⋅Na₂O Photochromic Glass in Faded State

Abstract

CdO-based oxide glasses exhibit the marked photoconductivity when exposed to the light with the photon energy corresponding to the absorption edge. This leads us to expect that the dark conductivity also originated from an electronic process. In order to understand the conduction mechanism of such type of glasses electric conduction and dielectric relaxation of 47.5CdO⋅47.5SiO₂⋅5Na₂O glass were measured.
The optical gap was much greater than the energy gap evaluated from the activation energy for electric conduction by assuming interband transition. The dielectric relaxation originated from ionic diffusional motion and correlated closely with the electric conduction was observed. These results and presence of Na⁺ ions in glass leads us to the conclusion that the electric conduction is ascribed to the transport process of the Na⁺ ion.