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

(GeTe sub(4)) sub(100-x)Ag sub(x) and (GeTe sub(4)) sub(100-x)(AgI) sub(x) glasses were prepared by a melting-quenching method. The glass electrical conductivity was investigated by both electrochemical impedance spectroscopy at different temperatures from 283 K to 333 K and four-probe method at room temperature (293 K). 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 (GeTe sub(4)) sub(100-x)Ag sub(x) glasses are mainly electronic conductive. On the other hand, the electrical conductivities of (GeTe sub(4)) sub(100-x)(AgI) sub(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 E sub(a) and the pre-exponential factor [sigma] sub(0) 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 (GeTe sub(4)) sub(100-x)Ag sub(x) and (GeTe sub(4)) sub(100-x)(AgI) sub(x) glasses are done and the importance of the Ag role is underlined.