Structural phase transitions in the Bi1−x La x FeO3 system

Crystal structure of Bi0.9Sm0.1Fe1−xMnxO3 multiferroics

“…Several structural models were considered for the x = 0.30 sample and after an initial screening using Le Bail fittings an orthorhombic Imma model, adapted from ref. 16, was selected for full Rietveld analysis. Fig.…”

Magnetically Driven Dielectric and Structural Behavior in Bi0.5La0.5FeO3

“…6 Electron and x-ray diffraction studies of x=0.25 showed that the samples comprised of coarse and fine grains of the nominal compositions x=0.1 and x=0.45 respectively. 7 Increasing the synthesis temperature, it was found that the composition of the grains changed to a situation where finer grains were rich in bismuth and iron and no longer contained La 3+ ions and the coarse phase remained. 7 In addition to variations due to synthesis conditions, structural characterisation of some of the phases can prove challeng-ing.…”

“…7 Increasing the synthesis temperature, it was found that the composition of the grains changed to a situation where finer grains were rich in bismuth and iron and no longer contained La 3+ ions and the coarse phase remained. 7 In addition to variations due to synthesis conditions, structural characterization of some of the phases can prove challenging. For instance the 'Pnam' phase, which has been successfully applied to other lanthanide dopants, has been suggested to contain a more complex octahedral tilt system, leading to a quadrupled axis, perhaps analogous to that seen in NaNbO 3 .…”

Strain-Driven Nanoscale Phase Competition near the Antipolar–Nonpolar Phase Boundary in Bi0.7La0.3FeO3 Thin Films

“…This result combined with the extracted lattice parameters (Figure d) indicates a second orthorhombic phase that agrees closely with both the incommensurate Imma (00γ) s 00 superstructure and Pnma phases that have been previously observed. ,, The Pnma phase is the most widely reported nonpolar phase in the rare earth-alloyed BiFeO 3 system, ,, but there has been some disagreement over whether the Imma (00γ) s 00 superstructure phase is an intermediate nonpolar phase. To further complicate phase identification, the Imma (00γ) s 00 superstructure phase was initially incorrectly indexed as a conventional Imma phase with secondary parasitic phases. , This oversimplified assignment was subsequently amended based on the persistence of the superstructure peaks with varied synthesis conditions. , A second Pn 2 1 a (00γ) s 00 superstructure has also been reported in bulk Bi 0.7 La 0.3 FeO 3 and has been differentiated from the Imma (00γ) s 00 superstructure only by minute changes in the superstructure diffraction peaks. , We can rule out the presence of either of the two superstructured phases because satellite peaks are not observed in the X-ray diffraction patterns (Supporting Information, Figure S1) nor in transmission electron microscopy (TEM) selected area electron diffraction (SAED, discussed later). The lack of both quarter-order and superstructure satellite diffraction peaks confirms that the tensile-strained heterostructures grown on GdScO 3 are a single nonpolar Pnma phase.…”

“…As the lanthanum content increases, things get more interesting as there is a reported polar-to-nonpolar phase transition. − As noted, there remains disagreement over the exact nature of this phase progression from the ferroelectric R 3 c to the paraelectric Pnma end members . For instance, first-principles calculations have predicted a direct transition from the rhombohedral R 3 c to the orthorhombic Pnma phase akin to a MPB-like transition with several quasi-energy-degenerate phases occurring at x ≈ 0.3. , Others have reported the existence of intermediate orthorhombic phases (i.e., an antipolar Pbam or an incommensurate nonpolar Imma phase) between the R 3 c and Pnma phases. ,,,− Despite these reports, the nature of the orthorhombic phases near the so-called MPB-like transition and their strain and field dependence are still a matter of discussion.…”