cg5b00525_si_002.cif (454.75 kB)
Reversible Exsolution of Nanometric Fe2O3 Particles in BaFe2–x(PO4)2 (0 ≤ x ≤ 2/3): The Logic of Vacancy Ordering in Novel Metal-Depleted Two-Dimensional Lattices
dataset
posted on 2015-09-02, 00:00 authored by Ignacio
Blazquez Alcover, Rénald David, Sylvie Daviero-Minaud, Dmitry Filimonov, Marielle Huvé, Pascal Roussel, Houria Kabbour, Olivier MentréWe show here that the exsolution
of Fe2+ ions out of
two-dimensional (2D) honeycomb layers of BaFe2(PO4)2 into iron-deficient BaFe2–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 observed a
systematic full ordering between Fe ions and vacancies (VFe) that denote unprecedented easy in-plane metal diffusion driven
by the Fe2+/Fe3+ redox. Besides the discovery
of a diversity of original depleted triangular ∞{Fe2/3+2–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
(Fe2/3+) to antiferromagnets for x = 2/3
(Fe3+).
