Electrical and dielectric properties of As₁₀Ge₁₅Te₇₅Ag_x glasses

Abstract

This paper analyses the effect of the addition of varying amounts of silver in concentrations from 0 to 10.0 at.% to As₁₀Ge₁₅Te₇₅ glass on d.c. and a.c. conductivities, dielectric constant and various allied parameters in the temperature range 83-383 K and the frequency range from d.c. to 50 MHz. The activation energy of d.c. conductivity increases with silver content up to 1.0 at.% and shows a reversal in the trend with higher percentages (5.0 and 10.0 at.%). The a.c. conductivity and memory switching behaviour are not altered by the addition of silver. The dielectric data suggest a dipole-type relaxation mechanism. The dielectric data corroborate the observed conductivity data in suggesting a probable increase in Te-chain breakages leading to an increase in the number of charged dangling bonds with silver content up to 1.0 at.% and, at higher percentages of silver, alloy formation occurs resulting in the reversal of the trend. Most of the data can be explained by the ‘charged dangling bond’ model of Mott, Davis and Street (1975) and ‘valence-alternation pairs’ (VAPs) and ‘intimate valence-alternation pairs’ (IVAPs) suggested by Kastner, Adler and Fritzsche (1976).