Oxygen Nonstoichiometry Study of LaSr3Fe3O10 in the Temperature Range 25-650°C

Neutron diffraction method has been applied to study structure-to conductivity changes of Ruddlesden-Popper phase LaSr3Fe3O10 in the temperature range 25 - 650°C. 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 650°C. 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 650°C. 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 3.83Angstrom at 25°C to 3.69Angstrom at 650°C.JRC.F.3-High Flux and Future Reactor