Tetragonal YBaFe{sub 4}O{sub 7.0}: A stoichiometric polymorph of the '114' ferrite family
- CRISMAT, CNRS-ENSICAEN 6 Bd Marechal Juin, 14050 Caen (France)
- Bragg Institute, Australian Nuclear Science and Technology Organization, PMB 1, Menai, NSW 2234 (Australia)
- Materials Science Division, Argonne National Laboratory 9700 S. Cass Avenue, Argonne, IL 60439 (United States)
The exploration of the phase diagram of the ferrite YBaFe{sub 4}O{sub 7+{delta}} versus the oxygen content {delta} and temperature shows the complex crystal chemistry of this system. Besides the cubic form (F4 Macron 3m), which is observed up to 600 Degree-Sign C and for 0<{delta}{<=}0.65, a stoichiometric tetragonal form ({delta}=0) is isolated below 300 Degree-Sign C that is stable only in the absence of oxidizing atmosphere. The resolution of the structure of this new YBaFe{sub 4}O{sub 7.0} form, from combined neutron and synchrotron data, in the space group I4 Macron , shows significant displacements of the atoms with respect to the cubic form, especially concerning the oxygen atoms surrounding the barium cations. The decrease of several Ba-O distances around the underbonded barium cations is explained by the existence of hybridized Ba{sup (2-{delta})+}-O{sup 2-}-Fe{sup (2+{delta})+} bonds, in agreement with Moessbauer spectroscopy. The role of coulombic repulsions in the [Fe{sub 4}O] and [Fe{sub 4}] tetrahedra of the [Fe{sub 4}]{sub {infinity}} sublattice on the structural transition is also discussed. - Graphical abstract: A new form of YBaFe{sub 4}O{sub 7} '114' ferrite which is only stable in oxygen free atmosphere, even at room temperature has been prepared. This new ferrite has its structure closely related to the cubic form YBaFe{sub 4}O{sub 7+{delta}} but differently from the latter which is stable for 0<{delta}<0.65, it requires a rigorous oxygen 'O{sub 7}' stoichiometry, i.e., {delta}=0. We describe herein the phase diagram of the oxides YBaFe{sub 4}O{sub 7+{delta}} and we determine the structure of this new YBaFe{sub 4}O{sub 7.0} form, from combined neutron and synchrotron data. Highlights: Black-Right-Pointing-Pointer Oxygen stoichiometry control in '114' YBaFe{sub 4}O{sub 7+d} ferrites. Black-Right-Pointing-Pointer A new structural transition leading to a new form of YBaFe{sub 4}O{sub 7+d} '114' ferrite for d=0. Black-Right-Pointing-Pointer Structural resolution from combined neutron and synchrotron data. Black-Right-Pointing-Pointer Phase diagram of the oxides YBaFe{sub 4}O{sub 7+d}.
- OSTI ID:
- 22012196
- Journal Information:
- Journal of Solid State Chemistry, Vol. . 191; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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