Effect of γ-irradiation on silver-sheathed Bi1.6Pb0.4Ba2Ca2Cu3O10 tapes

Specimens with nominal composition Bi_1.6Pb_0.4Ba₂Ca₂Cu₃O₁₀ were prepared using the powder-in tube technique. The effect of γ-irradiation at room temperature on the superconducting properties have been investigated using x-ray diffraction, resistivity measurements and I-V characteristics. The intensities of the main diffraction peaks decrease by about 25%, however, the peak positions do not change with γ-irradiation up to a dose of 400 MR. The normal state resistance R(T) increases gradually up to a dose of 100 MR, whereas at higher doses, the effect of irradiation becomes rather negligible. The transition temperature T_c decrease slightly and the transition temperature width ΔT broadens at doses below 100 MR with almost no change at higher doses up to 400 MR. At relatively low magnetic fields and low γ doses, the critical current densities J_c(B) increase with γ-irradiation, while the effect of γ-irradiation at relatively high magnetic fields is hardly observable. These results are discussed and explained in terms of the effect of γ-rays on the weak links grain boundaries and Josephson junctions between the grains.