Conductivity and Crystal Structure of ( C 5 H 5 NH ) 5Ag18 I 23 A Two‐Dimensional Solid Electrolyte

Abstract

The solid electrolyte pentapyridinium 18‐silver iodide, , has a crystal structure which allows the Ag⁺ ions to move in only two dimensions, perpendicular to its hexagonal c‐axis. The structure consists of face‐sharing iodide tetrahedra which provide a network of pathways for diffusion of the Ag⁺ ions. Planes of (formally) groups, which occupy a considerable proportion of the crystal space, block the motion of Ag⁺ ions in the c‐axis direction. Crystals of belong to space group with lattice constants , , and the unit cell contains one formula unit. There are 55 tetrahedral sites for the Ag⁺ ions in seven crystallographically nonequivalent sets of sites; as expected, the distribution of Ag⁺ ions over these sites is markedly nonuniform. The low specific conductivity of this solid electrolyte is consistent with its two‐dimensionality.