Reversible Exsolution of Nanometric Fe₂O₃ Particles in BaFe_2-x(PO₄)₂ (0 ≤ x ≤ 2/3):The Logic of Vacancy Ordering in Novel Metal-Depleted Two-Dimensional Lattices

Journal Article · Wed Aug 12 04:00:00 EDT 2015 · Crystal Growth and Design

DOI:https://doi.org/10.1021/acs.cgd.5b00525· OSTI ID:1225095

Alcover, Ignacio Blazquez; David, Rénald; Daviero-Minaud, Sylvie; Filimonov, Dmitry; Huvé, Marielle; Roussel, Pascal; Kabbour, Houria; Mentré, Olivier ^[1]

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1. CNRS-UMR

We show here that the exsolution of Fe²⁺ ions out of two-dimensional (2D) honeycomb layers of BaFe₂(PO₄)₂ into iron-deficient BaFe_2–x(PO₄)₂ phases and nanometric α-Fe₂O₃ (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 Fe²⁺/Fe³⁺ redox. Besides the discovery of a diversity of original depleted triangular _∞{Fe^2/3+_2–xO₆} 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 = 2/3 (Fe3+).

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: FOREIGNOTHER
• OSTI ID: 1225095
• Journal Information: Crystal Growth and Design, Journal Name: Crystal Growth and Design Journal Issue: 9 Vol. 15; ISSN 1528-7483
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: ENGLISH