Oxygen ion dynamics in pyrochlore-type ionic conductors: Effects of structure and ion–ion cooperativity

We summarize recent studies of oxide ion dynamics in ionically conducting defect pyrochlores of general formulae Ln 2 Ti 2 − y Zr y O 7 . Unit cell volume, structural disorder, and ion–ion interactions, are all relevant in determining ion hopping probability and thus the mobility of oxide ions at high temperatures. At enough low temperatures ion hopping is scarce and oxide ion dynamics are restricted to local displacements within the cage.