ESR and 57Fe Mossbauer Spectroscopy Study of Fe-doped SrBi2Nb2O9

Solid solutions of Bi2SrNb2-2xFe2xO9-delta have been obtained by solid-phase synthesis. The electronic state and nature of the local environment of iron atoms in the SrBi2Nb2O9 matrix with a layered perovskite-like structure were studied by ESR and Mossbauer spectroscopy. In the ESR spectra of samples of Bi2SrNb2-2xFe2xO9-delta (x <= 0.04) solid solutions an intensive asymmetric line in the low-field region with the main feature at g = 4.27, weakly pronounced peak g = 6.15 and shoulder g similar to 9, and also an intensive broad (Delta B-pp similar to 50-150 mT) band centered around g similar to 2.0 is present. The Mossbauer spectrum of the compound Bi2SrNb2-2xFe2xO9-delta is represented by an asymmetric doublet with isomer shift (IS) similar to 0.3, and quadrupole splitting (QS) similar to 0.5 mm/s. The shape of the doublet is reproduced by the superposition of two doublets with small and high IS and QS values. About 85% of the spectral area of the paramagnetic part of the spectrum is represented by the doublet Fe3+(1) with IS = 0.31 +/- 0.04, QS = 0.45 +/- 0.04 mm/s correlated with Fe3+ ions in regular axial positions. The remaining part is represented by the doublet Fe3+(2) with IS = 0.5 +/- 0.1, QS = 0.7 +/- 0.2 mm/s from the Fe3+ ions in defect environment.