Bulg. J. Phys. vol.34 no.s1 (2007), pp. 219-225

Oxygen Nonstoichiometry Study of LaSr3Fe3O10 in the Temperature Range 25−650oC

S. Neov1, O. Prokhnenko2, N. Velinov3, V. Kozhukharov3, D. Neov4, L. Dabrowski5
1Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Tsarigradsko Chaussee 72, BG-1784, Sofia, Bulgaria
2Hahn-Meitner Institut, Berlin, Germany
3University of Chemical Technology and Metallurgy, Sofia, Bulgaria
4Joint Research Centre - Institute for Energy, Petten, The Netherlands
5Institute of Atomic Energy, Otwock - Swierk, Poland
Abstract. Neutron diffraction method has been applied to study structure-to-conductivity changes of Ruddlesden-Popper phase LaSr3Fe3O10 in the temperature range 25-650oC. Structure parameters have been obtained by Rietveld analysis of high-resolution neutron diffraction spectra. Experimental data shows that the structure symmetry of LaSr3Fe3O10 is tetragonal, space group I4/mmm, and persists from ambient temperature to 650oC. The thermal expansion of a and b-axes is linear, while c-axis shows small positive deviation from linearity. The oxygen content decreases from 9.8 at room temperature to 9.4 at 650oC. The loss of oxygen is attended by bonds length changes mainly in the triple-perovskite layers of the structure. It has been established that part of the interatomic Fe-O and La(Sr)-O distances decrease with increasing temperature and as a result, the thickness of the inner layer formed by FeO6 octahedra decreases from 3.83 Å at 25oC to 3.69 Å at 650oC.

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