Mossbauer and XAFS studies of the effect of compositional disorder on the local structure of Pb₂FeSbO₆

X-ray absorption spectroscopic (XAS) and Mo center dot ssbauer investigations have been carried out to obtain information on the local environment of Fe ions in Pb2FeSbO6 (PFS) samples with different degree of the Fe3+ and Sb5+ ordering. Analysis of Mo center dot ssbauer spectra shows, that the fraction of doublet component in the spectrum of the disordered PFS sample is significantly larger, than that of the ordered one, however singlet component still persists, indicating the presence of the compositionally ordered regions. The Fe K-spectrum absorption for the ordered PFS sample exhibits the lowest pre-edge intensities, indicating that Fe position is close to the oxygen octahedron center. The higher amplitude of this peak for the disordered sample provides evidence for structural distortions, involving Fe displacement off the octahedra centers. Additional support to this conclusion provides the structure of absorption spectra, which gave substantially higher Debye-Waller factor of Fe-O shell for disordered sample as compared to the ordered one.