Crystals of this cubic compound, I¯43d - Td6 (a = 2.222nm, Z = 4), were studied. One of the 2 crystallographically non-equivalent Rb+ ions was 9-fold coordinated to Cl- ions. The other, in effect, had a (7+2)-coordination to Cl- ions. All of the Cu+ ions were tetrahedrally coordinated to Cl- ions. Each of 2 of the 4 crystallographically non-equivalent Cu+ ions had a very large Cu+-Cl- separation. The arrangement of the [CuCl4] tetrahedra was complex; sharing mainly corners, and some edges. The Cu+ ions in at least one set of positions were disordered. That is, there were 12 Cu+ ions in a set of 16c positions. At 298K, the specific conductivity at 1kHz was equal to 3.2 x 10-5S/cm. At 420K, it was equal to 1.1 x 10-3S/cm. A straight Arrhenius plot was obtained, and the activation enthalpy for motion was 0.35eV. Two octahedra and two 5-cornered pyramids of Cl- ions connected the [CuCl4] tetrahedral, via face-sharing, throughout the crystal structure. It was suggested that this material was a true solid electrolyte, but a poor one; with a considerable correlation of the motions of the Cu+ charge carriers.

S.Geller, S.Xie: Journal of Solid State Chemistry, 1986, 63[2], 316-25