Ionic conductivity of glasses in the MI + M 2S + (0.1Ga 2S 3 + 0.9GeS 2) system (M = Li, Na, K and Cs)

Abstract

In this study, the base 0.1Ga 2S 3 + 0.9GeS 2 was chosen because it was found that it could be combined with all of the alkali sulfides to yield glasses over the same relatively wide glass-forming composition range. Both M 2S and MI, where M = Li, Na, K and Cs, were added to form broad glass-forming composition ranges to systematically study the ionic conductivity in these ionic conducting chalcogenide glasses as a function of the alkali ion radius. As expected, additions of both alkali sulfide (M 2S) and alkali iodide (MI) increase the conductivity of the glass. For the 0.6M 2S + 0.4(0.1Ga 2S 3 + 0.9GeS 2) glasses, however, the conductivity only increases slightly with the addition of NaI. The ionic conductivities show significant differences between the Li 2S, Na 2S and K 2S, Cs 2S glasses due to the large differences in their activation energies. The alkali radius effect on the activation energy was analyzed and discussed based on the modified Anderson and Stuart model.