Synthesis and structural studies of cation-substituted Aurivillius phases ASrBi2Nb2TiO12

We report here a novel method to prepare high-quality samples of the three layered oxides ASrBi₂Nb₂TiO₁₂ACa, Sr or Ba using the pre-formed intermediates ABi₂Nb₂O₉ and SrTiO₃. The room temperature structures were refined using synchrotron X-ray and Neutron powder diffraction data in the orthorhombic space group B2cb. This symmetry arises as a consequence of cooperative tilting of the BO₆ octahedra in the [ASrNb₂TiO₁₀]²⁻ perovskite-like slabs and a polar displacement of the cations. The structure is characterized by extensive cation disorder but lacks appreciable oxygen vacancies.