Ionic conduction in As 2S 3Ag 2S, GeS 2GeSAg 2S and P 2S 5Ag 2S glasses

Abstract

The glass-forming region in the system PSAg was determined and density, thermal expansion, dc conductivity and the transport number of Ag ions were measured for P 2S 5Ag 2S glasses found in the PSAg system. The results for the transport number measurement show that P 2S 5Ag 2S glasses are purely ionic conductors owing to the Ag ion migration, like most of the As 2S 3Ag 2S and GeS 2GeSAg 2S glasses reported previously. Glass structure and ionic conduction processes in As 2S 3Ag 2S, GeS 2GeSAg 2S and P 2S 5Ag 2S glasses are discussed, based on their ionic conductivity and density data. The structural concept of α-Ag 2S was applied to these glasses, which suggests that the Ag ions in the glasses are distributed in the available Ag ion sites in the non-conducting framework composed of both S anions and As, Ge or P cations. In each system the ionic conductivity increases linearly with increasing Ag +/total cation (%) in glass composition, the determining factor being the activation energy for ionic conduction alone. Thus, the activation energy in these glasses depends predominantly upon the molar ratio of Ag ions to total cation in the glass, irrespective of the kind of system. Small differences in the activation energy among the three systems can be interpreted as arising from differences in the field strength of As, Ge and P cations.