Superconductivity in the Re1-zCDzBa2Cu3O7-δ (Re = Y, Nd, Sm, Gd, Dy, Ho, Yb) systems

Ac electrical resistance R(t) and powder X-ray diffraction measurements have been performed on the pseudoquaternary systems RE1-xCdxBa2Cu3O7-δ with RE = Y, Nd, Sm, Gd, Dy, Ho and Yb for O ≤ x ≤ 1.0. Powder x-ray diffraction patterns reveals that although impurity phase shows up in the samples as Cd concentration x increases, but the majority phase of the samples are of the 123 perovskite oxygen deficiency type structure. Substitution of the RE elements with Cd produces the effect of changing the normal state resistance from metallic behavior to semiconducting behavior as x increases for all system. However, the effects of Cd concentration x on the superconducting transition temperature Tc are different from different RE elements and can be roughly assorted into two different types. In one case, increasing Cd concentration x produces no appreciable effect on Tc for x ≤ 0.5 for RE elements such a Y, Gd and Ho. While for RE = Dy, Nd, Tc decreases monotonically as x increases