Structural, hyperfine and Raman properties of RE2FeSbO7 compounds

Pyrochlores of the RE2FeSbO7 type were synthesized by ball-milling followed by annealing in free atmosphere at high temperatures. The samples prepared were characterized by X-ray diffraction, Raman spectroscopy and 57Fe Mössbauer spectroscopy, at room temperature. The results showed that RE2FeSbO7 compounds have a cubic structure, i.e., Fd-3m (#227) space group, and that a site disorder takes place for the RE's of larger ionic radii. Lattice parameters, Raman bands and quadrupole splittings were shown to depend correlatedly on the RE ionic radius. This behavior is discussed in terms of the pyrochlore crystallographic structure.