New defect-perovskite oxides related to the yttrium-barium-copper oxide superconductor

$LaBa_2CuCo_2O_8$ and $LaBa_2Cu_2CoO_{7.4}$ possessing defect-perovskite structures related to $YBa_2Cu_3O_7$ (123) have been prepared. The cobalt in both the phases substitutes for the plane copper [Cu(2)] sites, preserving the Cu---O chains of the (123) structure. Accordingly, removal of oxygen from the new phases transforms the orthorhombic structure to the tetragonal structure of $YBa_2Cu_3O_{7-6}$. $LaBa_2CuCo_2O_8$ prepared above $1000^0C$ adopts a disordered cubic perovskite structure