Four solid-state phases were found in Cu4Cs1-xRbxI2Cl3 when x was less than 0.36 and the temperature was greater than 295K. The α-phase was isostructural with Ag4RbI5 and the α’-phase was thought to belong to a P213 sub-group of the α-phase. The β-phase existed only within a narrow temperature range, when x was less than 0.36, was rhombohedral and transformed to the α’-phase. The γ-phase was orthorhombic and transformed to the β-phase, when x was less than 0.36, or directly to the α-phase, when x was greater than 0.36. There was a triple-point when x was 0.36 and the temperature was 399K. The α and α’ phases attained conductivities greater than 0.73S/cm at 419K, and the activation enthalpies for the motion of Cu+ ions were of the order of 0.11eV.

S.Geller, A.K.Ray, T.Sakuma: Solid State Ionics, 1983, 9-10, 1227-32