Rubidium silver iodide

From Wikipedia, the free encyclopedia

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]

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]

Rubidium silver iodide –family is a group of compounds and solid solutions which are isostructural with the RbAg4I5 alpha modification. The examples of such advanced superionic conductors with mobile Ag+- and Cu+-cations are: KAg4I5, NH4Ag4I5, K1-xCsxAg4I5, Rb1-xCsxAg4I5, CsAg4Br1-xI2+x, CsAg4ClBr2I2, CsAg4Cl3I2, RbCu4Cl3I2, KCu4I5 and others [5-8].

[edit] References

  1. ^ a b Smart, Lesley and Elaine A. Moore (2005). Solid State Chemistry: An Introduction. CRC Press, p. 192. ISBN 0748775161. 
  2. ^ 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. 
  3. ^ 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. 
  4. ^ Geller, S. (July 1967). "Crystal Structure of the Solid Electrolyte, RbAg4I5". Science 157 (3786): 310–312. doi:10.1126/science.157.3786.310. 

[5] Geller S., Akridge J.R., Wilber S.A. Crystal structure and conductivity of the solid electrolyte α-RbCu4Cl3I2 // Phys. Rev. B 1979. V.19. P. 5396 – 5402.

[6] Hull S. Keen D.A., Sivia D.S., Berastegui P. Crystal Structures and Ionic Conductivities of Ternary Derivatives of the Silver and Copper Monohalides - I. Superionic Phases of Stoichiometry MAg4I5: RbAg4I5, KAg4I5, and KCu4I5 // J.Solid State Chemistry 2002. V. 165. P. 363-371.

[7] Despotuli A.L., Zagorodnev V.N., Lichkova N.V., Minenkova N.A. New high conductive CsAg4Br1-xI2+x (0.25 < x <1) solid electrolytes // Sov. Phys. Solid State 1989. V.31. P. 242-244.

[8] Lichkova N.V., Despotuli A.L., Zagorodnev V.N., Minenkova N.A., Shahlevich K.V. Ionic conductivity of solid electrolytes in the two- and three-components AgX –CsX (X = Cl, Br, I) glass-forming systems // Sov. Electrochem. 1989. V.25. P.1636-1640.