Mechano-chemical synthesis of RbAg4I5 and KAg4I5 crystals and their silver ion conducting properties

Abstract

A high-energy-ball-milling process was applied to the synthesis of the RbAg4I5 and KAg4I5 crystalline phases, which were known to show high Ag+ ion conductivity 2.7 × 101 Sm-1 at room temperature2,3). RbI, KI, and AgI were used as raw materials for the mechanical synthesis of the RbAg4I5 and KAg4I5 phases. Only 20 min-ball milling of a mixture of RbI and AgI led to the formation of RbAg4I5 phase, and the powder sample after 140 min-ball milling was containing only RbAg4I5 phase. On the other hand, the preparation of the sample containing only KAg4I5 phase needed the ball-mill treatment more than 50 h. The obtained RbAg4I5 and KAg4I5 samples showed high ion conductivity more than 101 Sm-1 at room temperature, and the conductivities were almost same as those of the RbAg4I5 and KAg4I5 crystalline phases reported by Owens et al.2,3). The DC polarization measurements suggested that main carrier of the ball-milled samples was silver ions and the silver ion transport numbers of the ball-milled samples were almost unity.