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Rubidium silver iodide

Rubidium silver iodide, formula RbAg₄I₅, is an unusually conductive crystal, with the conductivity involving movement of the silver ions within the crystal lattice. It was discovered while searching for chemicals which had the ionic-conductivity properties of alpha-phase silver iodide at temperatures below the 146 °C for AgI.^[1]

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It can be formed by melting together^[2] or grinding together^[3] stoichiometric quantities of rubidium iodide and silver (I) iodide. The published conductivity is 25 siemens per metre (IE a 1mm x 1mm x 1cm bar would have a resistance of 400 ohms along the long axis).

The crystal structure is composed of sets of iodine tetrahedra sharing faces, through which the silver ions are able to diffuse.^[4]

It was proposed around 1970 as a solid electrolyte for batteries, and has been used in conjunction with electrodes of silver and of RbI₃.^[1]

References

^ ^a ^b Smart, Lesley and Elaine A. Moore (2005). Solid State Chemistry: An Introduction. CRC Press, p. 192. ISBN 0748775161.
^ Popov, A. S.; Kostandinov, I. Z.; Mateev, M. D.; Alexandrov, A. P.; Regel, Liia L. (May 1990). "Phase analysis of RbAg4I5 crystals grown in microgravity". Microgravity Science and Technology 3: 41-43. Bibcode: 1990MiST....3...41P.
^ Peng H.; Machida N. Shigematsu T. (2002). "Mechano-chemical Synthesis of RbAg4I5 and KAg4I5 Crystals and Their Silver Ion Conducting Properties". Journal of the Japan Society of Powder and Powder Metallurgy 49 (2): 69-74.
^ Geller, S. (July 1967). "Crystal Structure of the Solid Electrolyte, RbAg4I5". Science 157 (3786): 310-312. doi:10.1126/science.157.3786.310.