STUDY OF THE MODULATED STRUCTURE OF BI2SR2CAFE2OX

The ceramics and single crystals of the Bi2Sr2CaFe2Ox compound were sy nthesized. The X-ray diffraction data showed orthorhombic symmetry. Th e lattice parameters are equal to a = 5.464 Angstrom, b = 5.453 Angstr om, c = 31.313 Angstrom The crystal structure is described by the prim itive Bravais lattice with the possible space groups Pbmm, Pbm2 and Pb 2(1)m. The obtained X-ray patterns show the presence the incommensurat e structural modulation with the following parameters: the modulation vector lies in the (100)-plane, the value of the wave-vector component q(b) = 0.22(3). The comparison of the obtained results with data for Fe-doped Bi2Sr2CaCu2Ox and Bi2Sr3Fe2Ox are presented. No magnetic pecu liarities of the compound were found. Mossbauer measurements of the ce ramic samples indicate the presence mainly of Fe3+ oxidation state and Fe4+ (about 20%). The decrease of the quadrupole-splitting values for 2212Fe in comparison with Fe-doped 2212Cu was revealed that may be co nnected with higher symmetry of the local environment of Fe atoms in 2 212Fe.