High Frequency Alternating Current Conductivity, Nuclear Magnetic Resonance Relaxation, and Short Range Motion of Ions in Sulfide Glasses

Abstract

The alternating current (ac) frequency responses for several sulfide ionically conductive glasses were investigated in the frequency range from 1 kHz to 1 GHz, which corresponds to the Larmor and probing frequencies for nuclear magnetic resonance (NMR) relaxation experiments. The additional conductivity under high frequency ac fields showed Arrhenius behavior in the temperature range studied (25 to 95°C). A frequency dependence of activation energy, , for the additional conductivity was observed. showed a plateau region with an ac frequency range covering the NMR Larmor frequencies. NMR spin echo experiments were carried out. The static quadrupolar and the heteronuclear dipolar contributions to the NMR lineshape were circumvented by the spin echo experiments. The activation energies obtained, , were consistent with plateau values for each glass composition. The consistency of these two experiments suggests that the additional conductivity is caused by the forced short‐range motion of the mobile ions, while the NMR relaxation experiments characterize the short range thermal motion in the temperature range of 220 to 380 K. Based on the experimental observations of this study combined with the concepts from the Anderson‐Stuart model, the weak electrolyte theory and the ion‐ion repulsion models, a simple qualitative interpretation for the ionic conduction in glasses is proposed. The ionic motion in glasses is controlled by: (i) the coulombic attraction energy, , between the ion under consideration and its oppositely charged environment; (ii) the strain energy, , for the ion going through a bottleneck; and (iii) the mobile ion‐ion repulsion energy, .