SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF 5 LAYER COPPER TITANIUM-OXIDE PEROVSKITES

The synthesis and characterization of six members of the ordered quint uple copper titanium perovskite series Ln(2)Ba(2)CaCu(2)Ti(3)O(14) are reported. Structural characterization, carried out by a combination o f powder X-ray and powder neutron diffraction and EXAFS, shows full or dering of the cations for Ln = Sm, Eu, Gd in the tetragonal space grou p P4/mmm with the B type cations stacked in the order Cu-Ti-Ti-Ti-Cu. For Ln = Nd partial disorder on both the a and B cation sublattices oc curs and oxygen is incorporated between the CuO2 layers. In La2Ba2CaCu 2Ti3O14 there is full disordering on both the A and B cation lattices leading to a simple cubic unit cell. When Ln = Tb and Dy, the symmetry of the structure is reduced to an orthorhombic cell, though the B cat ion stacking is maintained. In all materials the TiO6 octahedra are di storted. The in-plane Cu-O distances are similar to those found in hig h-temperature superconductors and are significantly shorter than those found in the corresponding quadruple copper titanium lanthanide perov skites.