Electrical, Magnetic and Superconducting Properties of the High-Tc Superconductor Bi2Sr2Ca1-xRExCu2O8+δ (RE=Nd and Pr)

Abstract

Structure, resistivity and susceptibility have been studied in the Bi₂Sr₂Ca_1-x RE _x Cu₂O_8+δ (RE=Nd and Pr) system. The samples with 0≦x≦1 have a single phase of the Bi₂Sr₂CaCu₂O_8+δ structure. The oxygen concentration, 8+δ, is estimated as about 8.3 which is independent of the RE composition x. The T _c increases slightly with x in the range of x≦0.10 and remains constant (∼85 K) for 0.10≦x≦0.25, then decreases linearly with x for 0.25≦x≦0.55. Superconductivity disappears for the samples with x≧0.55 in both cases. The Nd and Pr ions in the samples were both determined to be trivalent from the susceptibility data. The results show that the hole concentration in [Cu–O] plays a most significant role in the occurrence of superconductivity in the Bi–Sr–Ca–Cu–O system.