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Title: Reversible Exsolution of Nanometric Fe 2O 3 Particles in BaFe 2-x(PO 4) 2 (0 ≤ x ≤ 2/3):The Logic of Vacancy Ordering in Novel Metal-Depleted Two-Dimensional Lattices

We show here that the exsolution of Fe 2+ ions out of two-dimensional (2D) honeycomb layers of BaFe 2(PO 4) 2 into iron-deficient BaFe 2–x(PO 4) 2 phases and nanometric α-Fe 2O 3 (typically 50 nm diameter at the grain surface) is efficient and reversible until x = 2/3 in mild oxidizing/reducing conditions. It corresponds to the renewable conversion of 12 wt % of the initial mass into iron oxide. After analyzing single crystal X-ray diffraction data of intermediate members x = 2/7, x = 1/3, x = 1/2 and the ultimate Fe-depleted x = 2/3 term, we then observed a systematic full ordering between Fe ions and vacancies (V Fe) that denote unprecedented easy in-plane metal diffusion driven by the Fe 2+/Fe 3+ redox. Besides the discovery of a diversity of original depleted triangular {Fe 2/3+ 2–xO 6} topologies, we propose a unified model correlating the x Fe-removal and the experimental Fe/V Fe ordering into periodic one-dimensional motifs paving the layers, gaining insights into predictive crystahemistry of complex low dimensional oxides. When we increased the x values it led to a progressive change of the materials from 2D ferromagnets (Fe2+) to 2D ferrimagnets (Fe2/3+) to antiferromagnets for x =more » 2/3 (Fe3+).« less
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Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystal Growth and Design; Journal Volume: 15; Journal Issue: 9
American Chemical Society
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org:
Country of Publication:
United States