It was noted that Ag and Na had qualitatively different diffraction-determined ionic distributions on the conduction planes of a -alumina host. The possibility that this could lead to differing conduction mechanisms was investigated by introducing Cd2+ ions into both compounds and measuring the resultant mixed-ion distributions. A system of the form, Ag1.22-yCdy/2Al11O17.11, where y was equal to 0, 0.10, 0.41 or 1.11, and a system of the form, Na1.22-yCdy/2Al11O17.11, where y was equal to 0, 0.22, 0.45 or 1.22, were investigated by means of single-crystal X-ray diffraction. The difficulties of applying diffraction techniques to highly disordered systems of this type were considered, and it was shown that some of these difficulties could be resolved by taking account of additional physical and chemical information. Qualitatively different mechanisms were detected in the 2 cases, and it was concluded that aliovalent substitution could be a useful general tool for studying ionic conduction mechanisms in crystalline systems.

K.Edström, J.O.Thomas: Solid State Ionics, 1995, 80[3-4], 245-50