SILVER AS A DOPANT AND AS A CONSTITUENT IN AS-AG-TE GLASSES - ELECTRICAL-CONDUCTIVITY

Electrical conductivity data (from 200 to 360 K) on fifteen glass comp ositions of the As-Ag-Te system are reported and discussed. The glasse s were prepared using a two-stage melt-quenching method. For the (As2T e3)(1-x)Ag, glasses, features are seen in the electronic properties, c orresponding to a change in the role of Ag from a dopant (for Ag less than or equal to 1 at.%), to a constituent (for Ag > 1 at.%.). At this composition, step-like changes occur, in the activation energy for el ectrical conductivity and in the pre-exponential factor. Examination o f the data indicate that, as a dopant, Ag acts as neutral scattering c entres for charge carriers. As a constituent, Ag enhances the hopping channel for conductivity near the valence band edge.