A theoretical analysis was made of O2– diffusion mechanisms in a nanoporous complex oxide 12CaO·7Al2O3. This material could be viewed as being a positively charged framework, arranged in sub-nm sized cages, which hosted extra-framework O2– ions which occupied 1-in-6 cages. By using both classical molecular-dynamics simulations and ab initio calculations, it was demonstrated that the diffusion of O2– species was dominated by the exchange of framework and extra-framework O2– ions rather than by an interstitial diffusion mechanism. The results permitted rationalization of the experimentally observed high oxide ion conductivity of 12CaO·7Al2O3 and of the stability of its lattice under positive ion-beam irradiation.

Mechanisms of Oxygen Ion Diffusion in a Nanoporous Complex Oxide 12CaO·7Al2O3. P.V.Sushko, A.L.Shluger, K.Hayashi, M.Hirano, H.Hosono: Physical Review B, 2006, 73[1], 014101 (10pp)