we have explored the stability of oxy-halides in the Ba-Fe-O-X system (X=F, Cl). In this sense, we have prepared four samples in the BaFeClxOy system. Depending on the halogen content two polypypes (hchc)-4H and (chchh)2 -10H has been stabilized.In the atomically-resolved HAADF images obtained in an aberration corrected TEM microscope the anion substructure was initially observed. In this image, the halogen distribution through the anionic sublattice is visualized. From this, it is evidenced that halogen are not coordinated to the Fe atom but only to the larger barium ones. Our aim is to obtain a detailed structural characterization of the four BaFeClxOy samples with high resolution powder diffractometer D2B in order to establish how the oxygen rearrangement is modified by the incorporation of halides in the anionic sublattice as well as to accurately locate the halogen atom in the structure.