This solid electrolyte was unique in that, in spite of having some filled Cu+ ion sites in even the most favorable conduction pathway, and a low ratio (232:108) of available sites to Cu+ ions, it nevertheless exhibited a good activation enthalpy (0.21eV) and a reasonable conductivity (0.0044S/cm at 300K, 0.032S/cm at 420K). The crystals belonged to the space group, R¯3c, there were 12 formula units per rhombohedral unit cell, and there were 8 octahedral clusters of Rb+ ions in a rhombohedral cell. A Cl- ion was located at the center of each Rb+ ion octahedron. All of the Rb+ ions had a 9-fold coordination to Cl- ions. The Cu+ ions were distributed over 11 sets of tetrahedral sites and 1 set of sites which had a 3-fold coordination to Cl- ions. None of the tetrahedra shared faces. However, there were Cl- octahedra and square pyramids which did share faces with the tetrahedra and thus formed pathways for the movement of Cu+ ions through the crystal. The octahedra and pyramids were empty, thus indicating that the residence time of the Cu+ ions in them was very short. The nature of the structure and of the Cu+ ion distribution forced the Cu+ ion motions to be highly correlated.

J.M.Gaines, S.Geller: Journal of the Electrochemical Society, 1986, 133[7], 1501-7