Structural Studies of Five Layer Aurivillius Oxides: A 2 Bi 4 Ti 5 O 18 (A = Ca,Sr,Ba and Pb)

Abstract

The room temperature structures of the five layer Aurivillius phases A₂Bi₄Ti₅O₁₈ (A = Ca, Sr, Ba and Pb) have been refined from powder neutron diffraction data using the Rietveld method. The structures consist of [Bi₂O₂]²⁺ layers interleaved with perovskite-like [A₂Bi₂Ti₅O₁₆]²⁻ blocks. The oxides were found to be orthorhombic (space group B2cb) as a consequence of tilting of the TiO₆ octahedra coupled with cation displacement. The tilting is a consequence of the mismatch between the Bi₂O₂ and perovskite-like layers.