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

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Abstract
Structure, resistivity and susceptibility have been studied in the Bi2Sr2Ca1-x RE x Cu2O8+δ (RE=Nd and Pr) system. The samples with 0≦x≦1 have a single phase of the Bi2Sr2CaCu2O8+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.