Studies on Fast Ion Transport in Silver Sulphide Halogenides

The need for solid state ionics with fast ion transport at or near room temperature has tempted researchers to look for such materials and study their relevant properties for battery and other applications. One group of such candidates discovered early is the Silver Sulphide halogenides with their simple structure endowed with a disordered manifestation of Silver ions. The convenient phase transition exhibited by them at nearby room temperature has attracted them as good solid-state ionic materials. We were tempted to study the nature of ion diffusion in them using a reaction coordinate approach with the phonons excited in these materials. In the present paper we discuss the results of our investigation on AgSBr and AgSI on the nature of ion transport and the role such transport plays in deciding them as fast ion materials. Unlike a simulation study, in the present work we estimate the dynamics of all the relevant ions in deciding the jump frequency of Silver ion in such a lattice in the frame work of phonon field and hence obtain the diffusion profile of the jumping Ag+ ion. The results of the calculation are compared with the existing experimental results and also with other earlier calculations.