INcorporating Transition Metals in Ferroelectric Oxides

School of Chemistry, The University of Sydney
â—‹Brendan J Kennedy Qingdi Zhou Scott Mckenzie Chris Ling

There is considerable practical and fundamental interest in developing multiferroic materials that exhibit the unusual co-existence of ferroelectricity and ferromagnetic and display coupling between these. One strategy to prepare such oxides is to incorporate transition metals into ferroelectric oxides such as the Aurivillius oxides. In the present presentation we shall describe recent efforts to prepare such oxides. Two systems shall be presented in some detail, firstly we describe a novel method to prepare high quality samples of the three layered oxides ASrBi2Nb2TiO12 A = Ca, 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. Next we will describe efforts to replace the Ti with paramagnetic ions such as Cr, Mn and Fe. Here we find there is a limit to the amount of the transition metal that can be incorporated with the high quality samples of the type Sr2Bi2Nb2.5M0.5O12 being prepared. The structures of these oxides will be described.