Novel Nanorod Precipitate Formation in Neodymium and Titanium Codoped Bismuth Ferrite

Abstract

The discovery of unusual nanorod precipitates in bismuth ferrite doped with Nd and Ti is reported. The atomic structure and chemistry of the nanorods are determined using a combination of high angle annular dark field imaging, electron energy loss spectroscopy, and density functional calculations. It is found that the structure of the BiFeO3 matrix is strongly modified adjacent to the precipitates; the readiness of BiFeO3 to adopt different structural allotropes in turn explains why such a large axial ratio, uncommon in precipitates, is stabilized. In addition, a correlation is found between the alignment of the rods and the orientation of ferroelastic domains in the matrix, which is consistent with the system's attempt to minimize its internal strain. Density functional calculations indicate a finite density of electronic states at the Fermi energy within the rods, suggesting enhanced electrical conductivity along the rod axes, and motivating future investigations of nanorod functionalities.

The atomic structure and chemistry of Fe-rich steps on antiphase boundaries in Ti-doped Bi0.9Nd0.15FeO3

“…1 Whilst much of the Ti doping enters the perovskite structure as a randomly distributed B-site dopant, uncompensated Ti doping on the B-site causes precipitation of NdO x nanorods, with a novel corestructure just two atoms across. 2 The nanorods are present due to the ex-solution of Nd ions 3 and are accompanied by the formation of vacancies (V Nd /// ) in the perovskite matrix that compensate for the Ti substitution onto Fe sites (Fe Ti • ).…”

Tungsten Bronze Barium Neodymium Titanate (Ba6–3nNd8+2nTi18O54): An Intrinsic Nanostructured Material and Its Defect Distribution

“…While full simulations of inelastic scattering in the sample would be necessary to accurately quantify the column occupancies from experimental maps, the internal normalisation procedure described has been shown to yield reliable results when applied to samples of known compositions 31 . to-noise images 32 , which allow the determination of atomic column coordinates with picometer precision [33][34][35] . Unless otherwise stated, all images shown in this manuscript were acquired in this fashion.…”

“…Unless otherwise stated, all images shown in this manuscript were acquired in this fashion. The positions of the heavy-ion-containing A-site (Nd and Ba) columns were determined by 2D fitting of Gaussian profiles to each atomic column using the iMtools software 36 as used in previous quantitative atomic resolution electron microscopy studies [33][34][35]37 . The left edges of the images were systematically avoided due to possible scan distortions.…”

Maghemite-like regions at the crossing of two antiphase boundaries in doped BiFeO3

“…The present APB cross was in material that was probably too thick for good BF STEM, and also contained some bending across the area of interest, making the achievement of perfect imaging conditions at all points almost impossible. Performing a simulation using density functional theory, as used in some of our Salih et al two antiphase boundaries in doped BiFeO 3 of Cros s ing previous work, 13 is also unrealistic due to the huge number of atoms that are required. Thus, while the oxygen positions in the model are not perfect, they are within *25 pm of the correct positions, which is the maximum likely displacement due to spontaneous polarisation (c.f.…”