2 Diffusion in alkali and alkaline earth halides

Cyclic Corrosion and Chlorination of an FeCrAl Alloy in the Presence of KCl

“…Alkali chlorides are good ionic conductors at 600°C, since electrical current is carried solely by ions [33]. The diffusion of chloride ions in KCl has been reported to occur by the jump of an ion into a neighbouring anion vacancy, the activation energy for a single anion vacancy jump being 0.95 eV [34].…”

“…Thus, at 600°C, single-crystal a-alumina is an extrinsic semiconductor with E a = 0.4 eV, conduction being dominated by impurity states in the crystal [35]. Based on [33,35] the ionic conductivity of single-crystal KCl at 600°C is estimated to be 10 10 -10 12 larger than the ionic conductivity of single-crystal alumina. Thermally grown alumina scales on high temperature alloys differ from the material investigated in [35], because alumina scales are both polycrystalline and relatively impure.…”