Superconductivity in the solid solutions Y_nLa_2-n+xBa_4-xCu₆O_14+y (n=0, 1, 2)

The synthesis of a range of superconducting copper perovskites of the general formula YLaBaCu O (n=0, 1, 2) is reported. These materials have been characterised in terms of their lattice parameters, oxygen stoichiometry and superconducting critical temperature, T. Substitution of yttrium by lanthanum in YBACuO results in only minor changes in physical properties whilst replacement of barium by lanthanum causes a rapid drop in T. These results are interpreted in terms of the distribution of oxygen within the structure. It is concluded that all superconducting samples are essentially orthorhombic.