Silver alkali halide glasses and a vitreous analog of the RbAg₄I₅ superionic conductor

We report the existence of silver halide-rich glasses of a type not previously recognized. These contain only monovalent halides and represent perhaps the simplest ionic glasses yet realized. Despite the lack of the usual oxyanion matrix the new glasses show room temperature conductances which equal or exceed those of the best Ag⁺ glasses yet reported. Cu⁺ analogues have also been prepared. At the high conducting extreme apparently lies a vitreous state analog of the well-known crystalline conductor RbAg₄I₅. A crystalline analog of the latter FIC, CsAg₄ (I_0.45Cl_0.55)₅ forms metastably on careful devitrification of the glass. Like its prototype, it has a very high conductivity and exhibits a sharp C_p anomaly at low temperatures, -77°C, in the vicinity of which the activation energy for conductance changes abruptly.