Abstract
Ab initio investigation of the possibility of oxygen ion migration in non-stoichiometric bismuth titanate pyrochlore Bi1.5Ti2O6.25 has been performed. Density functional theory calculations together with the nudged elastic band method were used to estimate the O2– migration barriers. The migration energy barriers for the most favorable paths of oxygen migration related to O48f–O48f jumps are in the range 0.67–0.92 eV with the corresponding vacancy formation energy in the range 1.76–2.60 eV. These paths form extensive migration network in non-stoichiometric Bi1.5Ti2O6.25 which is sufficient for 3-dimensional O2– diffusion. The results show a good agreement with the experimentally obtained activation energy of oxygen diffusion in doped bismuth titanate pyrochlores with low dopant concentration.
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