CRYSTAL-STRUCTURE OF THE METALLIC LAYERED BARIUM LEAD-OXIDE

The structure of the layered oxide Ba4Pb3O10 has been refined by profile analysis from neutron powder diffraction data. The results of this study confirm the structural model proposed earlier. The material has tetragonal symmetry, space groupe I 4/mmm with lattice parameters a=4.2867(2)angstrom and c=30.217(1)angstrom. Its structure may be considered as an intergrowth of triple perovskite-like layers and single rock salt-like layers. The oxygens in the Pb(1)O2 layer are disordered over two positions along the c-axis, while the disorder of apical oxygens is confined to the ab plane along the a- and b-axis. The two crystallographycally independent lead atoms are octahedrally coordinated by oxygen. The Pb(1)O6 and Pb(2)O6 octahedra are slightly compressed and elongated along the c-axis respectively.