Tetragonal YBaFe{sub 4}O{sub 7.0}: a stoichiometric polymorph of the '114' ferrite family
- Materials Science Division
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{sup -}3m), which is observed up to 600 C and for 0 < {delta} {le} 0.65, a stoichiometric tetragonal form ({delta} = 0) is isolated below 300 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{sup -}, 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}]{infinity} sublattice on the structural transition is also discussed.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- SC DIVISION OF MATERIALS SCIENCE AND ENGINEERING
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 1048030
- Report Number(s):
- ANL/MSD/JA-73878; JSSCBI; TRN: US1204078
- Journal Information:
- Journal of Solid State Chemistry, Vol. 191, Issue Mar. 2012; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- ENGLISH
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