Crystal structure, magnetic, and dielectric properties of Aurivillius-type Bi3Fe0.5Nb1.5O9

Bi3Fe0.5Nb1.5O9 was synthesized using conventional solid state techniques and its crystal structure was refined by the Rietveld method using neutron powder diffraction data. The oxide adopts an Aurivillius-type structure with non-centrosymmetric space group symmetry A21am (a=5.47016(9) Å, b=5.43492(9) Å, c=25.4232(4) Å), analogous to other Aurivillius compounds that exhibit ferroelectricity. The Fe and Nb cations are disordered on the same crystallographic site. The [(Fe,Nb)O6] octahedra exhibit tilting and distortion to accommodate the bonding requirements of the Bi cations located in the perovskite double layers. Magnetic measurements indicate non-Curie–Weiss-type paramagnetic behavior from 300 to 6 K. Measurements of dielectric properties and electrical resistivity exhibited changes near 250–260 °C and are suggestive of a ferroelectric transition.