Rubidium silver iodide

Rubidium silver iodide is a ternary inorganic compound with the formula RbAg₄I₅. Its conductivity involves the movement of silver ions within the crystal lattice. It was discovered by Dr. Boone B. Owens while searching for chemicals which had the ionic conductivity properties of alpha-phase silver iodide at temperatures below 146 Ã‚°C for AgI.

RbAg₄I₅ can be formed by melting together or grinding together stoichiometric quantities of rubidium iodide and silver(I) iodide. The reported conductivity is 25 siemens per metre (that is a 1×1×10 mm bar would have a resistance of 400 ohms along the long axis).

The crystal structure is composed of sets of iodine tetrahedra; they share faces through which the silver ions diffuse.

RbAg₄I₅ was proposed around 1970 as a solid electrolyte for batteries, and has been used in conjunction with electrodes of silver and of RbI₃. Its conductivity does not exhibit substantial variation with changes in relative humidity.

Rubidium silver iodide family is a group of compounds and solid solutions that are isostructural with the RbAg₄I₅ alpha modification. Examples of such advanced superionic conductors with mobile Ag⁺ and Cu⁺ cations include KAg₄I₅, NH₄Ag₄I₅, K_{1−x}Cs_xAg₄I₅, Rb_{1−x}Cs_xAg₄I₅, CsAg₄Br_{1−x}I_2+x, CsAg₄ClBr₂I₂, CsAg₄Cl₃I₂, RbCu₄Cl₃I₂ and KCu₄I₅.

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