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Investigation of fe ions local states in perovskites La<sub>1-x</sub>Sr<sub>x</sub>Co<sub>0.98</sub><sup>57</sup>Fe<sub>0.02</sub>O<sub>3-y</sub> (x = 0.00; 0,25) by Mossbauer effect

Keywords:

A.S. Sigov - Dr.Sc. (Phys.-Math.), Professor, Member of RAS, President of the University, Moscow Technological University (MIREA). E-mail: pokatilov@mirea.ru V.S. Pokatilov - Dr.Sc. (Phys.-Math.), Professor , Moscow Technological University (MIREA). E-mail: pokatilov@mirea.ru A.O. Makarova - Ph.D. (Phys.-Math.), Senior Research Scientist, Moscow Technological University (MIREA). E-mail: a.o.konovalova@gmail.com V.V. Pokatilov - Junior Research Scientist, Moscow Technological University (MIREA). E-mail: v_pokatilov@mirea.ru V.V. Kitaev - Ph.D. (Eng.), Research Scientist, Southern Federal University (Rostov-on-don). E-mail: ktv2001@mail.ru E.F. Pevtsov - Ph.D. (Eng.), Director of the Center, Moscow Technological University (MIREA). E-mail: pevtsov@mirea.ru


Polycrystalline single-phase samples with a rhombohedral structure in the system La1-xSrxCo0.9857Fe0.02O3-y (x = 0,00; 0,25) were prepared with solid-state ceramic technology in air. Local structural and valence state of impurity iron ions in these perovskites were studied by the Mossbauer effect on the 57Fe nuclei at room temperature. Spectrum of impurity 57Fe nucleus in the sample LaCo0.98 57Fe0.02 O3 contains a single doublet, caused by the trivalent iron ions Fe3+ in a slightly distorted CoO6 octahedron. Replacement of the La3+ ions for Sr2+ in the perovskite La0.75Sr0.25Co0.9857Fe0.02O3-y leads to the appearance in the Mossbauer spectrum of the two local inequivalent states of the trivalent impurity iron ions. One of these states, caused by the trivalent iron ions in the octahedral Co3+O6. Other local state of iron ions is due to the position of trivalent iron ions in a square pyramidal oxygen environment in Co3+O5. The observed distortion of the oxygen octahedra and the formation of pyramidal complexes is due to both a significant difference of effective ionic radii of the ions of lanthanum and strontium and oxygen deficit.
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