Electrical and optical investigations in Te–Ge–Ag and Te–Ge–AgI chalcogenide glasses

(GeTe4)100-xAgx and (GeTe4)100-x(AgI)x glasses were prepared by a melting-quenching method. The glass electrical conductivity was investigated by both electrochemical impedance spectroscopy at different temperatures from 283K to 333K and four-probe method at room temperature (293K). Meanwhile, as a major factor determining the electrical conductivity of a solid, optical band gap was also studied. By comparing the electrical conductivity values and glass optical band gap evolution, it was found that (GeTe4)100-xAgx glasses are mainly electronic conductive. On the other hand, the electrical conductivities of (GeTe4)100-x(AgI)x glasses firstly show a monotonic decrease by increasing AgI up to 15 mol. %, and then an increase when the AgI content is higher than 15 mol. %. The activation energy and the pre-exponential factor show apparent turning point when AgI content is 15 mol. %, signifying a conductivity mechanism change. In this paper, correlations between the conductivity and hypothetical structures in (GeTe4)100-xAgx and (GeTe4)100-x(AgI)x glasses are done and the importance of the Ag role is underlined.