Ionic conductivity (Ag +) in AgGeSe glasses

Abstract

Ag x (Ge 0.25Se 0.75) 100− x (10≤ x≤25 at.%) ionic conductor glasses, prepared by a melt-quenching method, are investigated by impedance spectroscopy in the frequency range 5 Hz–2 MHz at different temperatures T from room temperature to 363 K. The conductivity of the glasses σ was obtained as a function of the silver concentration and the temperature. The temperature dependence of the ionic conductivity follows an Arrhenius type equation σ=( σ 0/ T)·exp(− E σ / kT). The activation energy of the ionic conductivity E σ and the preexponential term σ 0 were calculated. It was found that the room temperature conductivity increases by a factor of about 10 with increasing silver content (1.32 10 −5 S cm −1 at x=10 and 1.09 10 −4 S cm −1 at x=25), while the activation energy decreases from 0.367 to 0.339 eV. The diffusion coefficient of the Ag + ions was estimated. In addition, a model proposed by Elliott was applied to determine the activation energy of conductivity in the high-modifier-content region. The results are discussed in connection with structural aspects and with those published in the literature related to other chalcogenide and chalcohalide systems.