Ionic conductivity (Ag+) in AgGeSe glasses

Agx(Ge0.25Se0.75)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=(σ0/T)·exp(−Eσ/kT). The activation energy of the ionic conductivity Eσ and the preexponential term σ0 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.