Reversible Exsolution of Nanometric Fe2O3 Particles in BaFe2鈥?i>x(PO4)2 (0 鈮?x 鈮?2/3): The Logic of Vacancy Ordering in Novel Metal-De

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• 作者：Ignacio Blazquez Alcover ; R茅nald David ; Sylvie Daviero-Minaud ; Dmitry Filimonov ; Marielle Huv茅 ; Pascal Roussel ; Houria Kabbour ; Olivier Mentr茅
• 刊名：Crystal Growth & Design
• 出版年：2015
• 出版时间：September 2, 2015
• 年：2015
• 卷：15
• 期：9
• 页码：4237-4247
• 全文大小：864K
• ISSN：1528-7505

文摘

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鈥?i>x(PO₄)₂ phases and nanometric 伪-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 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 _{鈭?/sub>{Fe^2/3+2鈥?i>xO6} topologies, we propose a unified model correlating the x Fe-removal and the experimental Fe/VFe ordering into periodic one-dimensional motifs paving the layers, gaining insights into predictive crystal chemistry of complex low dimensional oxides. Increasing the x values led to a progressive change of the materials from 2D ferromagnets (Fe²⁺) to 2D ferrimagnets (Fe^2/3+) to antiferromagnets for x = 2/3 (Fe³⁺).}