Defect and dopant properties of the Aurivillius phase Bi4Ti3O12

Computer modelling techniques have been used to investigate the defect and oxygen transport properties of the Aurivillius phase Bi₄Ti₃O₁₂. A range of cation dopant substitutions has been considered including the incorporation of trivalent ions (M³⁺=Al, Ga and In). The substitution of In³⁺ onto the Bi site in the [Bi₂O₂] layer is predicted to be the most favourable. The calculations suggest that lanthanide (Ln³⁺) doping at the dilute limit preferentially occurs in the [Bi₂O₂] layer, with probable distribution over both the [Bi₂O₂] and the perovskite A-site at higher dopant levels. It is predicted that the reduction process involving Ti³⁺ and oxygen vacancy formation is energetically favourable. The energetics of oxide vacancy migration between various oxygen sites in the structure have been investigated.