Molecular dynamics simulation was employed to study oxygen ion diffusion in Ba2In2O5 having the brownmillerite structure. When the system was heated, the original orthorhombic cell changed to a tetragonal cell at 2300K. Inspection of the structure revealed that oxygen ions jumped from their original sites to the nearest vacant sites. The diffusion was restricted for sites around the tetrahedrally coordinated In ion, resulting in highly anisotropic diffusion on the ac plane. At 4600K it further transformed to an oxygen disordered cubic perovskite structure in which all oxygen ions contributed to diffusion. The predicted transition was consistent with the observed transition to a fast oxide-ion conductor for this compound, although the predicted temperature was overestimated. The effect of composition upon the transition was studied by simulating the A2B2O5 (A2+ = Ba, Sr, Ca; B3+ = Al, Fe, In) systems. From these results, oxide-ion conductors with lower transition temperatures could be predicted.

Molecular Dynamics Simulation of Oxygen Ion Diffusion in Ba2In2O5. Kanzaki, M., Yamaji, A.: Materials Science and Engineering B, 1996, 41[1], 46-9