Effect of synthesis conditions on the morphology and crystal structure of biferroic Bi5Ti3FeO15

The biferroic Aurivillius-phase Bi5Ti3FeO15 was obtained by molten salt synthesis (MSS) using an equimolar mixture of NaCl/KCl as the ionic solvent. The morphology, size and crystal structure of the material was strongly dependent on the synthesis conditions. Particles with plate-like morphology and high aspect relation were obtained with sizes ranging from 50 nm to 10 μm. Using conventional X-ray diffraction, it was qualitatively determined that at synthesis temperatures lower than 850 °C, the phase has a tetragonal structure, while at temperatures at or above 850 °C, the phase presents an orthorhombic structure. Synchrotron X-ray diffraction and Rietveld refinement were used to determine the crystal structure of the best crystallized phase in detail (synthesis temperature: 850 °C). The model that best fits the experimental data is the orthorhombic space group A21am. The lattice parameters (Å) determined are a=5.47722(6), b=5.44365(6) and c=41.17004(37). The crystalline particles obtained were used to obtain highly textured polycrystalline material with high densities (ρ>96% of theoretical maximum density).